*5.1.1. Approach 1*

The treatment of the radium content in TE-NORM using sequential chemical leaching was based on the individual extraction for each Ra species in the waste, according to the successive four steps (A.1–4). From the data obtained, it was found that the exchangeable radium species was removed from the waste. The removal percentages (%) for Ra226, Ra228, and Ra224 are 5.7 ± 2.4, 6.5 ± 1.4, and 3.1± 0.9%, respectively. These values are high if comparable to the exchangeable Ra species present in and extracted from phosphate ores [61].

In the second step of leaching (A.2), the data obtained show that the removal percentages (%) are found to be of 9.9 ± 0.4, 7.5 ± 0.9, and 11.8 ± 0.2 % for Ra226, Ra228, and Ra224, respectively. This leached part is related to the Ra fraction bounded to carbonate species (acidic fraction of species Ra). In step number three (A.3), it was found that the removal percentages of Ra226, Ra228, and Ra224 are 10.9 ± 1.4, 18.3 ± 2.5, and 19.6 ± 0.4%, respectively. This leached part is related to radium species bounded to metal-oxides such as the Fe-Mn-oxides [62]. The remaining part of radium species found bounded to organic matter and sulfides was leached through two substeps (A.4). The final removal percentages by this approach related to Ra226, Ra228, and Ra224 are 51.5 ± 2.1, 32.5 ± 4.1, and 41.9 ± 5.2%, respectively, as shown in Figure 5.

It is important to focus on the environmental and health impacts from the uncontrolled release of TE-NORM wastes [54, 34, 23]. Treatment of these wastes is of increasing interest because accumulation of large amounts with a significant activity may cause health risks to the workers through exposure, inhalation of radon (Rn222) decayed from radium, and/or ingestion of waste dust during the periodical maintenance of the equipment used. Treatment of TE-NORM wastes from many industries still needs more efforts. The traditional methods used before include subsurface disposal, volume reduction, use of scale and/or sludge inhibitors, recycling, and leaching using chemical solutions [55–57]. In addition, a simple extraction process is carried out using saline solutions and chemical solutions [41, 58] to removal of Ra226, Pb210, Rn220, Th232, Ra228, and Ra224 from TE-NORM wastes produced from oil and gas industry.

Sequential chemical treatment for radium in sludge or scale to reduce its activity concentration in oil and natural gas production fields is recommended. The proposed treatment method was carried out on the basis of two approaches using chemical solutions through four successive

Successive four steps were used to leachate the radium species in the waste of TE-NORM [59].

Before the treatment investigations, the activity concentrations of the main three radium isotopes were measured. It is found that the average activity level of Ra226, Ra228, and Ra224 were 11950 ± 1700, 1750 ± 200, and 1900 ± 250 Bq/kg, respectively. Due to the high accumulation of radium species in huge amounts and high activity concentrations causing health hazards to the environment and the workers, sequential chemicals treatment approaches are suggested

It is well known that the environmental behavior and toxicity of trace elements and radionu‐ clides depend strongly on their physicochemical forms (i.e., speciation) in the environment [60]. In this study, the applied treatments involve four steps achieved sequentially for each approach. Selective extraction of the different radium species present in TE-NORM waste, such as water-soluble species, exchangeable, carbonates, reducible species, oxidizable organics

The treatment of the radium content in TE-NORM using sequential chemical leaching was based on the individual extraction for each Ra species in the waste, according to the successive four steps (A.1–4). From the data obtained, it was found that the exchangeable radium species was removed from the waste. The removal percentages (%) for Ra226, Ra228, and Ra224 are 5.7 ± 2.4, 6.5 ± 1.4, and 3.1± 0.9%, respectively. These values are high if comparable to the

In the second step of leaching (A.2), the data obtained show that the removal percentages (%) are found to be of 9.9 ± 0.4, 7.5 ± 0.9, and 11.8 ± 0.2 % for Ra226, Ra228, and Ra224, respectively. This leached part is related to the Ra fraction bounded to carbonate species (acidic fraction of

exchangeable Ra species present in and extracted from phosphate ores [61].

as a new trend to reduce the human and environmental hazard potential.

steps.

98 Advances in Petrochemicals

**5.1. Approach of treatment**

becomes allowed.

*5.1.1. Approach 1*

 **individual extraction for each Ra species in the waste**  According to approach 1, the successive leaching steps released most of the radium species **Figure 5.** Sequential leaching of the radium content in TE-NORM was based on the individual extraction for each Ra species in the waste

**Figure 5 Sequential leaching of the radium content in TE-NORM was based on the** 

found in the treated TE-NORM waste. Also, from the data obtained, it is observed that the real removal percentages (%) of Ra226, Ra228, and Ra224 are 78 ± 2.8, 64.8 ± 4.1, and 76.4 ± 5.2%, respectively. There is variation in the leaching % for each Ra-isotope due to the radiochemical factors such as the differences in their half-lives. Figure 6 shows the leaching of the different Ra species in the waste. It is observed that the oxidizable Ra species is the main Ra fraction in this type of waste. This may be attributed to the high concentration of leaching solutions used to remove Ra species within the TE-NORM sludge waste. Therefore, the radium species in the treated waste using approach A can be ordered as: oxidizable > reducible > acidic > exchangeable. According to approach 1, the successive leaching steps released most of the radium species found in the treated TE-NORM waste. Also, from the data obtained, it is observed that the real removal percentages (%) of Ra226, Ra228, and Ra224 are 78 ± 2.8, 64.8 ± 4.1, and 76.4 ± 5.2%, respectively. There is variation in the leaching % for each Ra-isotope due to the radiochemical factors such as the differences in their half-lives. Figure 6 shows the leaching of the different Ra species in the waste. It is observed that the oxidizable Ra species is the main Ra fraction in this type of waste. This may be attributed to the high concentration of leaching solutions used to remove Ra species within the TE-NORM sludge waste. There‐ fore, the radium species in the treated waste using approach A can be ordered as: oxidiza‐ ble > reducible > acidic > exchangeable.

16

**Figure 6.** Distribution of radium species in T E NORM ludge using approach A

### **5.1.2 Approach 2**  *5.1.2. Approach 2*

**Step B.1** 

 In approach 2, the TE-NORM waste was treated sequentially using different chemical leaching , through four leaching steps. The de-aerated and de-ionized H2O (pH 6.7, 25 ± 1 CH3COONH4 (pH 6.8, 25 ± 1 C, 4 h) as water-soluble and exchangeable solutions for removal of Ra In approach 2, the TE-NORM waste was treated sequentially using different chemical leaching, through four leaching steps. The de-aerated and de-ionized H2O (pH 6.7, 25 ± 1°C, 4 h), 1M CH3COONH4 (pH 6.8, 25 ± 1°C, 4 h) as water-soluble and exchangeable solutions for removal of Ra species are used. The results showed that the leached percentages (%) of radium isotopes are 10.6 ± 1.5, 9.7 ± 1.2, and 11.2 ± 0.8 % for Ra226, Ra228, and Ra224, respectively (step B.1).

**Fig.6. D istribution of radium species in TEN O R M sludge using approach A**

C, 4 h), 1M

species are used. The results showed that the leached percentages (%) of radium isotopes are 10.6 ± 1.5, 9.7 ± 1.2, and 11.2 ± 0.8 % for Ra226, Ra228, and Ra224, respectively (step B.1). In the second leaching process (B.2), the acidic radium species such as carbonates, and in addition , some iron and manganese oxides are removed. The leaching percentages (%) of radium species are 12.8 ± 2.8, 15.2 ± 0.5, and 16.5 ± 1.2% for Ra226, Ra228, and Ra224, respectively. The remaining In the second leaching process (B.2), the acidic radium species such as carbonates, and in addition, some iron and manganese oxides are removed. The leaching percentages (%) of radium species are 12.8 ± 2.8, 15.2 ± 0.5, and 16.5 ± 1.2% for Ra226, Ra228, and Ra224, respec‐ tively. The remaining waste was leached through two successive substeps. The solutions used are selective to the reducible radium species in the waste, such as manganese oxides, amor‐ phous iron oxide, and moderately reducible phase (step B.3). The obtained removal percen‐ tages (%) of Ra226, Ra228, and Ra224 are 14.2 ± 1.2, 17.4 ± 3.1, and 19.0 ± 1.5%, respectively. Finally, the remaining waste was treated using oxidizing reagent solution, as a selective chemical agent to leach the oxidizable radium species in the waste (step B.4). The leached percentages (%) of the oxidizable Ra species are 53.3 ± 1.2, 48.4 ± 1.9, and 45.0 ± 2.3% for Ra226, Ra228, and Ra224, respectively, as shown in Figure 7.

waste was leached through two successive substeps. The solutions used are selective to the reducible radium species in the waste, such as manganese oxides, amorphous iron oxide, and moderately reducible phase (step B.3). The obtained removal percentages (%) of Ra226, Ra228, and Ra224 are From the data obtained from two leaching sequence mentioned above, it was found that using selective chemical solutions is more efficient when dealing with the different radium species present in the TE-NORM waste. Also, the data showed that the overall removal percentages (%) of all radium species are 90.9 ± 3.5, 86.7 ± 4.1, and 89.7± 6.2% for Ra226, Ra228, and Ra224, respectively. These values indicate that the amounts leached of the three radium isotopes by this approach are nearly the same. Figure 8 represents distribution of the actual removed (%)

and 45.0 ± 2.3 % for Ra226, Ra228, and Ra224, respectively, as shown in Figure 7.

**II. 1M CH3COONH4 (pH 6.8, 25 ± 1 o**

17

**I. deaerated & deionized H2O (pH 6.7, 25 ± 1 <sup>o</sup>**

**C, 4 hrs )** 

**C, 4 hrs)** 

14.2 ± 1.2, 17.4 ± 3.1, and 19.0 ± 1.5 %, respectively. Finally, the remaining waste was treated using

oxidizing reagent solution, as a selective chemical agent to leach the oxidizable radium species in the

waste (step B.4). The leached percentages (%) of the oxidizable Ra species are 53.3 ± 1.2, 48.4 ± 1.9,

Overview about Different Approaches of Chemical Treatment of NORM and TE-NORM Produced from Oil Exploitation http://dx.doi.org/10.5772/61122 101

**Figure 7 Sequential leaching of the radium content in TE-NORM was based on the Figure 7.** Sequential leaching of the radium content in TE-NORM was based on the individual extraction for each Ra species in the waste

C, 4 h), 1M C, 4 h) as water-soluble and exchangeable solutions for removal of Ra species are used. The results showed that the leached percentages (%) of radium isotopes are 10.6 ± toward different types of the radium species found in the treated TE-NORM waste. It is found that the high removal % of Ra226 is obtained for the radium oxidizable species. This is due to the high ability of the leaching solutions used in step (B.4) to remove the radium species from sludge waste. This conclusion confirms that the same behavior is obtained when using approach A. Therefore, the oxidizable Ra species is the main Ra fraction in waste. So, the net conclusion, the sequence of the different radium species present in the treated waste by leaching (%) can be ordered as: oxidizable > reducible > acidic > exchangeable as shown in Figure 8.  **individual extraction for each Ra species in the waste**  From the data obtained from two leaching sequence mentioned above, it was found that using

, some iron and manganese oxides are removed. The leaching percentages (%) of radium species are 12.8 ± 2.8, 15.2 ± 0.5, and 16.5 ± 1.2% for Ra226, Ra228, and Ra224, respectively. The remaining waste was leached through two successive substeps. The solutions used are selective to the reducible radium species in the waste, such as manganese oxides, amorphous iron oxide, and moderately reducible phase (step B.3). The obtained removal percentages (%) of Ra226, Ra228, and Ra224 are The overall removal (%) of the radium species using the both approaches (A and B) are illustrated in Figure 9. It is showed that the overall removal percentages of Ra226 and Ra224 are nearly the same when the waste is leached using approaches A and B. It is found that values of the overall removal % of Ra226 and Ra224 leached using solutions of approach A are 78% and 76%, respectively. On the other hand, it was found that the overall removal % using solutions of approach B is increased to ~90 % for Ra226 and Ra224. While the overall leached % of Ra228 is low comparable to Ra226 and Ra224 at the same leaching conditions, the obtained overall removal percentages of Ra228 are ~65% and 87.5% using solutions of the approaches A and B, respectively (Figure 9). The variation in the overall removal % between the leached Ra species from the TE-NORM sludge waste under the same leaching conditions is difficult to be explained. Finally, treatment of the sludge waste using solutions of approach B is more efficient compared to approach A, toward the overall removal percentages of Ra species. selective chemical solutions is more efficient when dealing with the different radium species present in the TE-NORM waste. Also, the data showed that the overall removal percentages (%) of all radium species are 90.9 ± 3.5, 86.7 ± 4.1, and 89.7± 6.2% for Ra226, Ra228, and Ra224, respectively. These values indicate that the amounts leached of the three radium isotopes by this approach are nearly the same. Figure 8 represents distribution of the actual removed (%) toward different types of the radium species found in the treated TE-NORM waste. It is found that the high removal % of Ra226 is obtained for the radium oxidizable species. This is due to the high ability of the leaching solutions used in step (B.4) to remove the radium species from sludge waste. This conclusion confirms that the

18

17

**I. deaerated & deionized H2O (pH 6.7, 25 ± 1 <sup>o</sup>**

**C, 4 hrs )** 

**C, 4 hrs)** 

**Exchangable Acidic R educible O xidisable O veral (A.1-4)**

**R a species**

, through four leaching steps. The de-aerated and de-ionized H2O (pH 6.7, 25 ± 1

In approach 2, the TE-NORM waste was treated sequentially using different chemical leaching, through four leaching steps. The de-aerated and de-ionized H2O (pH 6.7, 25 ± 1°C, 4 h), 1M CH3COONH4 (pH 6.8, 25 ± 1°C, 4 h) as water-soluble and exchangeable solutions for removal of Ra species are used. The results showed that the leached percentages (%) of radium isotopes are 10.6 ± 1.5, 9.7 ± 1.2, and 11.2 ± 0.8 % for Ra226, Ra228, and Ra224, respectively (step B.1).

1.5, 9.7 ± 1.2, and 11.2 ± 0.8 % for Ra226, Ra228, and Ra224, respectively (step B.1).

In the second leaching process (B.2), the acidic radium species such as carbonates, and in addition, some iron and manganese oxides are removed. The leaching percentages (%) of radium species are 12.8 ± 2.8, 15.2 ± 0.5, and 16.5 ± 1.2% for Ra226, Ra228, and Ra224, respec‐ tively. The remaining waste was leached through two successive substeps. The solutions used are selective to the reducible radium species in the waste, such as manganese oxides, amor‐ phous iron oxide, and moderately reducible phase (step B.3). The obtained removal percen‐ tages (%) of Ra226, Ra228, and Ra224 are 14.2 ± 1.2, 17.4 ± 3.1, and 19.0 ± 1.5%, respectively. Finally, the remaining waste was treated using oxidizing reagent solution, as a selective chemical agent to leach the oxidizable radium species in the waste (step B.4). The leached percentages (%) of the oxidizable Ra species are 53.3 ± 1.2, 48.4 ± 1.9, and 45.0 ± 2.3% for Ra226,

From the data obtained from two leaching sequence mentioned above, it was found that using selective chemical solutions is more efficient when dealing with the different radium species present in the TE-NORM waste. Also, the data showed that the overall removal percentages (%) of all radium species are 90.9 ± 3.5, 86.7 ± 4.1, and 89.7± 6.2% for Ra226, Ra228, and Ra224, respectively. These values indicate that the amounts leached of the three radium isotopes by this approach are nearly the same. Figure 8 represents distribution of the actual removed (%)

**Fig.6. D istribution of radium species in TEN O R M sludge using approach A**

In approach 2, the TE-NORM waste was treated sequentially using different chemical leaching

In the second leaching process (B.2), the acidic radium species such as carbonates, and in addition

14.2 ± 1.2, 17.4 ± 3.1, and 19.0 ± 1.5 %, respectively. Finally, the remaining waste was treated using

oxidizing reagent solution, as a selective chemical agent to leach the oxidizable radium species in the

waste (step B.4). The leached percentages (%) of the oxidizable Ra species are 53.3 ± 1.2, 48.4 ± 1.9,

and 45.0 ± 2.3 % for Ra226, Ra228, and Ra224, respectively, as shown in Figure 7.

**II. 1M CH3COONH4 (pH 6.8, 25 ± 1 o**

100 Advances in Petrochemicals

**5.1.2 Approach 2** 

*5.1.2. Approach 2*

**Step B.1** 

CH3COONH4 (pH 6.8, 25 ± 1

**Ra-226 Ra-228 Ra-224**

**Figure 6.** Distribution of radium species in T E NORM ludge using approach A

Ra228, and Ra224, respectively, as shown in Figure 7.

**leached %**

**leached %**

**Ra-226 Ra-228**

**Figure 8.** Distribution of radium species in TENORM s ludge u sin g approach B

**Fig.8. Overall removal percentages (%) of radium species leached from TENORM waste sludge using approaches A and B Figure 9.** Overall removal percentages (%) of radium species leached from TENORM waste sludge using approaches A **Fig. 9.**  and B

The sequential chemical treatment could be the key point for environmental-friendly leaching for TE-NORM waste to select the suitable chemicals for the treatment processes [33]. The sequential chemical treatment could be the key point for environmental-friendly leaching for TE-NORM waste to select the suitable chemicals for the treatment processes [33].

The sequential chemical treatment could be the key point for environmental-friendly leaching for TE-NORM waste to select the suitable chemicals for the treatment processes [33]. The other alternative process for treatment of these wastes is leaching or solubilization of the different The other alternative process for treatment of these wastes is leaching or solubilization of the different radionuclides. This is based on partial dissolution of the radionuclides using strong acids or by conversion of hardly or insoluble radionuclides forms to easily soluble salts. Within these merits, investigations were carried out to assess the direct leaching of radionuclides by HCl or HNO3 or by treating the waste with carbonate solutions followed by leaching the The other alternative process for treatment of these wastes is leaching or solubilization of the different radionuclides. This is based on partial dissolution of the radionuclides using strong acids or by conversion of hardly or insoluble radionuclides forms to easily soluble salts. Within these merits, investigations were carried out to assess the direct leaching of radionuclides by HCl or HNO3 or by

treating the waste with carbonate solutions followed by leaching the formed carbonates with dilute acid solution. The different conditions for the maximum removal of the radionuclides Pb210, Ra226, and Ra228 from the sludge and the scale wastes are given. From this table, it is clear that leaching with nitric acid produced better leaching efficiency for the removal of Pb210, Ra226, and Ra228 and then the use of hydrochloric acid. This is relating mainly to the oxidizing action of nitric acid. It is also

radionuclides. This is based on partial dissolution of the radionuclides using strong acids or by

conversion of hardly or insoluble radionuclides forms to easily soluble salts. Within these merits,

investigations were carried out to assess the direct leaching of radionuclides by HCl or HNO3 or by

treating the waste with carbonate solutions followed by leaching the formed carbonates with dilute

acid solution. The different conditions for the maximum removal of the radionuclides Pb210, Ra226,

and Ra228 from the sludge and the scale wastes are given. From this table, it is clear that leaching

20

with nitric acid produced better leaching efficiency for the removal of Pb210, Ra226, and Ra228 and

then the use of hydrochloric acid. This is relating mainly to the oxidizing action of nitric acid. It is also

20

formed carbonates with dilute acid solution. The different conditions for the maximum removal of the radionuclides Pb210, Ra226, and Ra228 from the sludge and the scale wastes are given. From this table, it is clear that leaching with nitric acid produced better leaching efficiency for the removal of Pb210, Ra226, and Ra228 and then the use of hydrochloric acid. This is relating mainly to the oxidizing action of nitric acid. It is also clear that treatment with carbonate before leaching adds some benefits to the removal efficiency. This can be related to the possible conversion of the sulfate salts to the carbonate, which is easily leachable by dilute acids.

Leaching the carbonate treated sludge and scale wastes by high acid concentration can produce better removal for the different radionuclides, Table 8, yet use of strong acid is not recom‐ mended for its hazardous action. Therefore, and out of the different leaching systems studied, it can be recommended that the treatment of both the sludge and the scale wastes by 10% Na2CO3 followed by leaching with 1 M HNO3 solution is recommended. This treatment will remove more than 70% of Pb210, Ra226, and Ra228 from scale waste and more than 55% of the same radionuclides from the sludge waste. It is also noted that the % removal of Ra226 is different than that of Ra228. This suggests that Ra226 is concentrated in different species of these wastes [63].


**Table 8.** Comparison of maximum % removal of environmental interest radionuclides by different methods

20

**exchangable Acidic reducible oxidisable O veral (B.1-4)**

**Ra-226 Ra-228** R **a-224**

**Ra-226 Ra-228** R **a-224**

**Figure 8.** Distribution of radium species in TENORM s ludge u sin g approach B

**Ra species**

**exchangable Acidic reducible oxidisable O veral (B.1-4)**

**Ra species**

**approach A approach B**

**Fig.7. Distribution of radium species in TENO RM sludge using approach B**

**approach A approach B**

**Ra-226 Ra-228 Ra-224**

**Radium species**

**Figure 9.** Overall removal percentages (%) of radium species leached from TENORM waste sludge using approaches A **Fig. 9.** 

**Fig.8. Overall removal percentages (%) of radium species leached from TENORM waste sludge using approaches A and B**

**Radium species**

The sequential chemical treatment could be the key point for environmental-friendly leaching

The sequential chemical treatment could be the key point for environmental-friendly leaching for

The other alternative process for treatment of these wastes is leaching or solubilization of the different radionuclides. This is based on partial dissolution of the radionuclides using strong acids or by conversion of hardly or insoluble radionuclides forms to easily soluble salts. Within these merits, investigations were carried out to assess the direct leaching of radionuclides by HCl or HNO3 or by treating the waste with carbonate solutions followed by leaching the

The other alternative process for treatment of these wastes is leaching or solubilization of the different radionuclides. This is based on partial dissolution of the radionuclides using strong acids or by conversion of hardly or insoluble radionuclides forms to easily soluble salts. Within these merits, investigations were carried out to assess the direct leaching of radionuclides by HCl or HNO3 or by treating the waste with carbonate solutions followed by leaching the formed carbonates with dilute acid solution. The different conditions for the maximum removal of the radionuclides Pb210, Ra226, and Ra228 from the sludge and the scale wastes are given. From this table, it is clear that leaching with nitric acid produced better leaching efficiency for the removal of Pb210, Ra226, and Ra228 and then the use of hydrochloric acid. This is relating mainly to the oxidizing action of nitric acid. It is also

for TE-NORM waste to select the suitable chemicals for the treatment processes [33].

**Ra-226 Ra-228 Ra-224** <sup>0</sup>

**Fig.8. Overall removal percentages (%) of radium species leached from TENORM waste sludge using approaches A and B**

The sequential chemical treatment could be the key point for environmental-friendly leaching for

The other alternative process for treatment of these wastes is leaching or solubilization of the different

radionuclides. This is based on partial dissolution of the radionuclides using strong acids or by

conversion of hardly or insoluble radionuclides forms to easily soluble salts. Within these merits,

investigations were carried out to assess the direct leaching of radionuclides by HCl or HNO3 or by

treating the waste with carbonate solutions followed by leaching the formed carbonates with dilute

acid solution. The different conditions for the maximum removal of the radionuclides Pb210, Ra226,

and Ra228 from the sludge and the scale wastes are given. From this table, it is clear that leaching

20

with nitric acid produced better leaching efficiency for the removal of Pb210, Ra226, and Ra228 and

then the use of hydrochloric acid. This is relating mainly to the oxidizing action of nitric acid. It is also

TE-NORM waste to select the suitable chemicals for the treatment processes [33].

TE-NORM waste to select the suitable chemicals for the treatment processes [33].

**Fig.7. Distribution of radium species in TENO RM sludge using approach B**

**0**

**Fig. 8**.

**0**

**Fig. 8**.

**2 0**

**4 0**

**6 0**

**8 0**

**100**

**Fig. 9.** 

**overall removal %**

**overall removal %**

and B

**2 0**

**leached %**

**4 0**

**leached %**

**6 0**

**8 0**

102 Advances in Petrochemicals

**100**

Now, interesting study was done by our team using the solvent extraction technique for treatment of TE-NORM at scales on the interior of a pipe used in exploration of gas and oil industry, and several parameters were studied, such as the effect of contact time, organic extractants concentration, organic liquid/solid ratio, temperature, effect of different aliphatic and organic diluents. From the data available up till now, it can be concluded that kerosene as a diluent has a good efficiency on the E % of the radionuclides with the different organic extractants used. The extraction percent order with different types of organic extractants for 226Ra, separation of 228Ra, 238U, 210Pb, and 40K at kerosene was found in the following order:

TOPO ≈ TBP > TBPO > DEHPA > TPPO > TPAsO for 226Ra TBP > TOPO > DEHPA > TBPO > TPPO > TPAsO for 228Ra TBP > DEHPA > TPPO > TBPO > TOPO > TPAsO for 238U TOPO > TBPO > TBP > DEHPA > TPAsO > TPPO for 210Pb TBP > DEHPA > TOPO > TBPO > TPAsO > TPPO for 40K

Also, our team examined and evaluated two surfactants as extracting agent for the removal of radium species from TE-NORM sludge produced from petroleum industry. In this investiga‐ tion, cationic and nonionic surfactants were used as extracting agents for the removal of radium radionuclides from the sludge waste. Two surfactants namely cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX100) were investigated as the extracting agents. Different parameters affecting the removal of both 226Ra and 228Ra by the two surfactants as well as their admixture were studied by the batch technique [64]. The influence of contact time on disso‐ lution/desorption of radium radionuclides (226Ra, 228Ra) from TE-NORM sludge waste using TX100 and CTAB surfactants was investigated. Transport and mass transfers of radium isotopes from the sludge might be a key process responsible for reducing radium from the sludge. To achieve maximum radium species removal, a specific period of time is required. The obtained results are represented in Table 9. It is obvious that the removal efficiency of radium isotopes is increased as the shaking time was increased and reach maximum after 60 minutes. The highest removal efficiency for <sup>226</sup>Ra was obtained using CTAB surfactant, and using TX100 surfactant for <sup>228</sup>Ra. However, further increase in the time of experiment leads to decrease of the removal efficiency [64].


**Table 9.** Effect of contact time on the removal efficiency (R, %) of 226Ra and 228Ra using 1% (w/v) surfactants solutions

Effect of surfactant concentration on the extraction of radium isotopes is regarded as an important parameter affecting the removal of radium isotopes from TE-NORM sludge waste. The removal efficiency of radium species for both surfactant solutions increased with increas‐ ing surfactant concentration up to 1%. At higher surfactants concentration, a slight decrease was observed in Table 10. The optimum concentrations are found to be 1% for both surfactants solutions. The effective removal of radium species from TE-NORM sludge can be explained by the increased solubility of radium species in the surfactant micelles. Generally, the change in the concentration of surfactant leads to change in its physical properties such as micelles formation and its solubilization effect for radium species or any contaminant (organic or inorganic species) present in TE-NORM sludge waste [65]. Therefore, the optimum surfactants concentrations are 1% for this treatment to avoid introduction of excess surfactants into sludge and avoid decrease in the radium removal %.

extractants used. The extraction percent order with different types of organic extractants for 226Ra, separation of 228Ra, 238U, 210Pb, and 40K at kerosene was found in the following order:

Also, our team examined and evaluated two surfactants as extracting agent for the removal of radium species from TE-NORM sludge produced from petroleum industry. In this investiga‐ tion, cationic and nonionic surfactants were used as extracting agents for the removal of radium radionuclides from the sludge waste. Two surfactants namely cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX100) were investigated as the extracting agents. Different parameters affecting the removal of both 226Ra and 228Ra by the two surfactants as well as their admixture were studied by the batch technique [64]. The influence of contact time on disso‐ lution/desorption of radium radionuclides (226Ra, 228Ra) from TE-NORM sludge waste using TX100 and CTAB surfactants was investigated. Transport and mass transfers of radium isotopes from the sludge might be a key process responsible for reducing radium from the sludge. To achieve maximum radium species removal, a specific period of time is required. The obtained results are represented in Table 9. It is obvious that the removal efficiency of radium isotopes is increased as the shaking time was increased and reach maximum after 60 minutes. The highest removal efficiency for <sup>226</sup>Ra was obtained using CTAB surfactant, and using TX100 surfactant for <sup>228</sup>Ra. However, further increase in the time of experiment leads to

**Time, min TX100 solution CTAB solution**

 16.0 ± 1.3 17.0 ± 1.4 20.4 ± 1.8 15.0 ± 1.3 22.0 ± 1.5 20.5 ± 1.8 22.7 ± 2.0 18.2 ± 1.6 25.0 ± 1.7 27.0 ± 2.1 26.0 ± 2.0 22.0 ± 1.3 15.7 ± 1.3 24.0 ± 2.2 23.7 ± 2.1 23.7 ± 2.0 8.2 ± 0.8 18.5 ± 1.6 4.2 ± 0.4 16.7 ± 1.5

**Table 9.** Effect of contact time on the removal efficiency (R, %) of 226Ra and 228Ra using 1% (w/v) surfactants solutions

Effect of surfactant concentration on the extraction of radium isotopes is regarded as an important parameter affecting the removal of radium isotopes from TE-NORM sludge waste. The removal efficiency of radium species for both surfactant solutions increased with increas‐ ing surfactant concentration up to 1%. At higher surfactants concentration, a slight decrease was observed in Table 10. The optimum concentrations are found to be 1% for both surfactants

**226Ra (R, %) 228Ra (R, %) 226Ra (R, %) 228Ra (R, %)**

TOPO ≈ TBP > TBPO > DEHPA > TPPO > TPAsO for 226Ra TBP > TOPO > DEHPA > TBPO > TPPO > TPAsO for 228Ra TBP > DEHPA > TPPO > TBPO > TOPO > TPAsO for 238U TOPO > TBPO > TBP > DEHPA > TPAsO > TPPO for 210Pb TBP > DEHPA > TOPO > TBPO > TPAsO > TPPO for 40K

104 Advances in Petrochemicals

decrease of the removal efficiency [64].


**Table 10.** Effect of surfactants concentrations on the removal efficiency (R, %) of 226Ra and 228Ra

The effect of temperature on the surfactants is not straightforward [66]. So that, temperature of surfactant solutions used for removal of radium species is an important parameter in surfactant-aided sludge washing process, and the experiments have been investigated with concentration of 1% TX100 and CTAB at 25–60°C. The results in Table 11 showed that the removal of Ra-isotopes are increased with increasing temperature and the removal of Ra species reach a maximum at 60°C using both surfactants solutions. The increase of Ra species removal efficiency is due to the properties of surfactants, where an increase in temperature generally results in an increase in the extent of solubility. The cloud point phenomenon occurs when a surfactant above its CMC causes the separation of the original solution into two phases when heated at a characteristic temperature called cloud point temperature. At this tempera‐ ture, surfactant is no longer soluble in water and solution becomes hazy and cloudy. Above the cloud point, micelles formed from surfactant molecules act as an organic solvent in liquid– liquid extraction and the analytes are partitioned between the micelles and the aqueous phases [67]. It has been mentioned that the cloud point extraction procedure not only effectively solubilizes and concentrates pollutants but also appears to offer a means to further the concentrated surfactant-enhanced wash solutions that have been used in soil treatment processes [68]. About 25% of the radium species were initially removed from the TE-NORM sludge by solubilization in surfactants solution. About 55–60% removal was achieved upon the temperature raise to 60°C as shown in Table 11.

Synergism in surfactants may be defined as any situation where mixtures of surfactants have superior properties when compared to the properties of any of the single surfactant alone [69].


**Table 11.** Effect of temperature on the removal efficiency (R, %) of 226Ra and 228Ra using surfactants solutions

There is usually a synergy effect for the CMC of surfactant mixtures (mixture of nonionic and ionic surfactant) [69]. Mixture of TX100 and CTAB surfactants showed synergistic interactions, which can be manifested as enhanced surface properties, spreading, and many other phe‐ nomena, as shown in Figure 5. The synergistic behavior of mixed surfactant systems can be exploited to reduce the total amount of surfactant used in a particular application resulting in the reduction of cost [70]. It was observed that the removal values of radium isotopes of mixed systems of both surfactants are higher than their corresponding values without mixing, which indicate synergistic interaction in mixed CTAB-TX100 as a chemical extraction system. Removal of 84% and 80% for 226Ra and 228Ra, respectively, are obtained using synergistic effect of 1% aqueous solution containing 1:1 of the two surfactants investigated. In other words, mixed micelle formation in aqueous solution can be greater than that of the individual surfactant, and explained by non-ideal solution theory [70]. Also, it was observed that combined extraction of cationic and nonionic surfactants was effective in removal of both 226Ra and 228Ra. Experiments indicated that removal efficiency was optimized (80–84%) when a mixture of 1% CTAB and 1% TX100 was employed at the ratio 1:1. The theoretical justification for this surfactants solution is based upon two hypotheses, first that surfactant micelles may sequester radium radionuclides which are sorbed to the TE-NORM sludge waste, and second that the surfactant micelles may increase the concentration of radium radionuclides in the aqueous phase. The developed chemical treatment process would enable to design an appropriate TE-NORM sludge washing strategy.
