*2.2.3.1.1.5 Standards and regulations for Cr(VI)*

According to the USEPA water standards, the maximum limit of Cr in drinking water is 0.1 mg/L which is based on the total Cr (EPA, 1990) [92]. Also, the allowable concentration of dischargeable Cr(VI) into surface water is below 0.05 mg/L; however, the permissible concentration of total Cr (Cr(VI), Cr(III) and other forms) is equal to 2 mg/L [93]. The American conference of governmental industrial hygienists' threshold limit time-weighted averages for Cr(VI) is 0.01 mg/m3 . In addition, the Canadian guidelines has indicated a limit of 0.05 mg/L for total Cr concentration in drinking water [94]. Krishnani et al. [95] reported that the maximum permissible limits of Cr(VI) to discharge into potable water, in land surface water, and industrial wastewater are 0.05, 0.1, and 0.25 mg/L, respectively. According to the Moroccan official bulletin (NM 03.7.001), the Russian federation [73], and the Indian standard [65, 94], the maximum allowable limits for Cr in drinking and domestic water are 0.05 and 0.5 mg/L for Cr(VI) and Cr(III), respectively.

#### *2.2.3.1.2 Copper*

*Water Chemistry*

**Table 6.**

is mostly toxic to higher plants at 100 μg/kg dry weights. Sinha et al. [79] reported that Cr is toxic for most agronomic plants at a concentration of about 0.5–5.0 mg/L in nutrient media and of 5–100 mg/g under soil condition. The Cr toxicity in plants affects photosynthesis in terms of CO2 fixation, photophosphorylation, electron

**Industry Cr(VI) concentration (mg/L)**

Hardware factory 60.0 Chrome tanning plant 3.7 Electroplating plant 1.0 Electropolishing plant 42.8 Tannery plant 3950.0 Tannery plant 100.0 Tannery plant 1770.0 Tannery plant 8.3 Electroplating plant 20.7 Electroplating plant 75.4

Given the different chemistries and malignity of Cr(III) and Cr(VI) complexes, the concentration determination of each chemical speciation rather than the total Cr concentration is often desired [81]. Indeed, Cr(VI) is mainly analyzed, and various methods to prevent its reduction have been developed. There are two main groups of Cr speciation methods: off- and online techniques [82]. The off-line methods use pretreatment techniques for separation and concentration of specific Cr species (in the samples) before its insertion into detection instruments. These pretreatment techniques can be (i) colored complex formation methods, (ii) soluble membrane filter techniques, (iii) chromatographic methods, (iv) electrochemical methods, (v) coprecipitation techniques, (vi) ion exchange techniques, (vii) separation using chelating resins, and (viii) solvent extraction. In the online methods, the separation system is coupled with detection system. These methods include (i) flow injection analysis, and (ii) high-performance liquid chromatography (HPLC) that includes ion chromatography (IC), (iii) ion pair chromatography (IPC), and (iv) reversed-phase

The globally acknowledged standard methods for selective Cr(VI) detection are spectroscopic techniques using diphenyl carbazide (DPC) method with a limit of detection (LOD) of 0.12 mg/L [83]. In general, the DPC spectrophotometric determination is an inexpensive and sensitive procedure that also permits the speciation of Cr. It is worth mentioning that de Andrade et al. [84, 85] have employed DPC for the flow injection spectrophotometric determination of Cr(VI). In this work, the authors combined the spectrophotometric procedure with the column preconcentration procedure. New reagents are used for Cr(VI) spectrophotometric determination. Andrle and Broekaert [86] suggested the selective determination of Cr(VI) based upon the formation of a complex between ammonium pyrrolidinedithiocarbamate and Cr(VI). To overcome ion interferences, Pyrzynska [83] proposed a new analysis based on the reaction of Cr(VI) with chromotropic acid (in acidic

transport, and enzyme activities as reported by H. Oliveira [76, 80].

*2.2.3.1.1.4 Cr(VI) detection methods*

*Industrial wastewater containing Cr(VI) [69].*

**54**

chromatography.

From the most common heavy metals that are often present in industrial wastewater, Cu is usually found at high concentrations in industrial discharges (**Figure 6**) [96]. Cu is an abundant trace element found in a variety of rocks and minerals. Over 90% of modern industrial enterprises need Cu products.

The Cu reserves and production (mines and concentrates) in major countries in 2014 are reported in **Table 7** [97]. Cu is involved in reduction, oxidation processes, adsorption/desorption, and dissolution processes which lead to many changes in its speciation. Cu is a transitional metal and appears in nature in four oxidation states: elemental copper Cu(0) (solid metal), Cu(I) cuprous ion, Cu(II) cupric ion, and rarely Cu(III). However in natural water systems, Cu can exist only in two different oxidation states, Cu(I) and Cu(II) [87]. The oxidation states of Cu depend on the concentration of oxygen.

In its oxidation state, Cu forms very stable complexes with both organic and inorganic ligands. The toxicity of serine and citrate is enhanced in case of estuarine bacteria, while Cu-amino acid and Cu-citrate are enhanced in case of *Daphnia* and algae, respectively [99]. In its pure form, Cu has outstanding criteria such as electrical and thermal conductivity, strong chemical stability, good corrosion resistance, and high plasticity and malleability, which makes it so attractive for industries.

#### **Figure 6.**

*Ecology of Cu. Colored arrows represent various aspects, namely, orange, elemental Cu fluxes; blue, human Cu interventions; green, human Cu intake; red, contamination [96].*


#### **Table 7.**

*Cu reserves and production (mines and concentrates) in major countries [97].*

### *2.2.3.1.2.1 Copper (II)*

As stated before, Cu is a redox-active element meaning it can easily go back and forth between the oxidized Cu(II) state and the reduced Cu(I) state [100]. The following Eqs. (7)–(9) represent the reduction processes for Cu ions:

**57**

*Pollution of Water Sources from Agricultural and Industrial Effluents: Special Attention…*

Cu(II) is suggested to be the primary species in nearly all natural waters. In this oxidation state, Cu forms very stable complexes with both organic and inorganic

In contrast, Cu(I) is unstable in aqueous solution and tends to change rapidly to Cu(II). Cu(II) forms strong complexes with the electron donor groups in organic

Many studies confirmed that an increased concentration of Cu(II) in the body leads to serious health problems [96, 98, 103]. Cu and Cu(II) is absorbed in the intestine and then transported to the liver and binds to albumin [96]. Due to its catalytic role, Cu can reduce human immunodeficiency and leads to symptoms of anemia, vomiting, neutropenia, hypopigmentation, bone abnormalities, and growth disorders. It was also related to abnormalities in the metabolism of glucose and cholesterol. Brewer et al. [100] also studied the many roles of Cu in human metabolisms and explained properly the different genetic diseases caused by this metal, namely, Wilson's disease, Menkes disease, and Alzheimer's disease. From an environmental point of view, the high concentration of Cu with an extreme acidity inhibits the ordinary development of plants and animals, reduce the biodiversity, contaminate water reservoirs, and even corrode infrastructure. Generally, sheep suffer plenty from Cu poisoning, because of the effects of Cu that manifest at fairly low concentrations [103].

The development of analytical methods for the selective detection and visualization of Cu(II) is significant. The common methods for the detection of Cu(II), as for Cr(VI), include liquid chromatography, electrochemical detection, spectrophotometry, solid-phase extraction coupled with atomic absorption spectroscopy, potentiometric techniques, X-ray fluorescence, atomic emission spectroscopy, and inductively coupled plasma mass spectrometry [104, 105]. According to Ramanjaneyulu et al. [106, 107], the existing reagents for the photometric determination of Cu permit the detection of 0.025–30 μg/mL Cu. For instance, the diethyldithiocarbamate reagent is considered one of the most frequently used reagents for Cu(II) determination with a LOD of 0.1 μg/L. Zagurskaya et al. [107] developed a spectrophotometric method of determination of Cu(II) with a ligand for a new coordination compound, the sodium salt of 4-phenylsemicarbazone 1,2-naphthoquinone-4-sulfonic acid (L). The formation of this new complex is accompanied by

The maximum permissible limits (MPL) for Cu in water are listed in **Table 8**. Furthermore, the USEPA has set a MPL for Cu discharges either in the soil or in wastewater. The MPL in the soil is equal to 100 mg/L, while the limit for wastewater

*2.2.3.1.2.2 Cu(II) effects on human health and environment*

Cu2+ + 2 e− ↔ Cu<sup>0</sup> (7)

Cu2+ + e<sup>−</sup> ↔ Cu<sup>+</sup> (8)

Cu<sup>+</sup> + e− ↔ Cu<sup>0</sup> (9)

2+ is believed to be the principal cationic hydrolysis product.

*DOI: http://dx.doi.org/10.5772/intechopen.86921*

ligands [101]. Cu2(OH)2

compounds (O, N, and S) [102].

*2.2.3.1.2.3 Cu detection methods*

a color change and LOD of 0.012 mg/L.

*2.2.3.1.2.4 Standards and regulations for Cu and its derivative*

*Pollution of Water Sources from Agricultural and Industrial Effluents: Special Attention… DOI: http://dx.doi.org/10.5772/intechopen.86921*

$$\text{Cu}^{2+} + 2\text{e}^- \leftrightarrow \text{Cu}^0 \tag{7}$$

$$\text{Cu}^{2+} + \text{e}^- \leftrightarrow \text{Cu}^\* \tag{8}$$

$$\text{Cu}^{\ast} \text{+ } \text{e}^{\text{-}} \leftrightarrow \text{Cu}^{0} \tag{9}$$

Cu(II) is suggested to be the primary species in nearly all natural waters. In this oxidation state, Cu forms very stable complexes with both organic and inorganic ligands [101]. Cu2(OH)2 2+ is believed to be the principal cationic hydrolysis product. In contrast, Cu(I) is unstable in aqueous solution and tends to change rapidly to Cu(II). Cu(II) forms strong complexes with the electron donor groups in organic compounds (O, N, and S) [102].

#### *2.2.3.1.2.2 Cu(II) effects on human health and environment*

Many studies confirmed that an increased concentration of Cu(II) in the body leads to serious health problems [96, 98, 103]. Cu and Cu(II) is absorbed in the intestine and then transported to the liver and binds to albumin [96]. Due to its catalytic role, Cu can reduce human immunodeficiency and leads to symptoms of anemia, vomiting, neutropenia, hypopigmentation, bone abnormalities, and growth disorders. It was also related to abnormalities in the metabolism of glucose and cholesterol. Brewer et al. [100] also studied the many roles of Cu in human metabolisms and explained properly the different genetic diseases caused by this metal, namely, Wilson's disease, Menkes disease, and Alzheimer's disease. From an environmental point of view, the high concentration of Cu with an extreme acidity inhibits the ordinary development of plants and animals, reduce the biodiversity, contaminate water reservoirs, and even corrode infrastructure. Generally, sheep suffer plenty from Cu poisoning, because of the effects of Cu that manifest at fairly low concentrations [103].

#### *2.2.3.1.2.3 Cu detection methods*

The development of analytical methods for the selective detection and visualization of Cu(II) is significant. The common methods for the detection of Cu(II), as for Cr(VI), include liquid chromatography, electrochemical detection, spectrophotometry, solid-phase extraction coupled with atomic absorption spectroscopy, potentiometric techniques, X-ray fluorescence, atomic emission spectroscopy, and inductively coupled plasma mass spectrometry [104, 105]. According to Ramanjaneyulu et al. [106, 107], the existing reagents for the photometric determination of Cu permit the detection of 0.025–30 μg/mL Cu. For instance, the diethyldithiocarbamate reagent is considered one of the most frequently used reagents for Cu(II) determination with a LOD of 0.1 μg/L. Zagurskaya et al. [107] developed a spectrophotometric method of determination of Cu(II) with a ligand for a new coordination compound, the sodium salt of 4-phenylsemicarbazone 1,2-naphthoquinone-4-sulfonic acid (L). The formation of this new complex is accompanied by a color change and LOD of 0.012 mg/L.

#### *2.2.3.1.2.4 Standards and regulations for Cu and its derivative*

The maximum permissible limits (MPL) for Cu in water are listed in **Table 8**. Furthermore, the USEPA has set a MPL for Cu discharges either in the soil or in wastewater. The MPL in the soil is equal to 100 mg/L, while the limit for wastewater

*Water Chemistry*

**Figure 6.**

**56**

**Table 7.**

*2.2.3.1.2.1 Copper (II)*

The United States

As stated before, Cu is a redox-active element meaning it can easily go back and forth between the oxidized Cu(II) state and the reduced Cu(I) state [100]. The

*Ecology of Cu. Colored arrows represent various aspects, namely, orange, elemental Cu fluxes; blue, human Cu* 

**Cu mine production /(ten thousand tons)**

3500 5.00 138.3 108.6

**Cu concentrate production /(ten thousand tons)**

**Percentage of global reserves/(%)**

Chile 20,900 29.86 575.0 274.7

Russia 3000 5.00 72.0 87.4 China 3000 4.29 192.3 764.9

Zambia 2000 2.58 75.6 70.9

*interventions; green, human Cu intake; red, contamination [96].*

Australia 9300 13.29 97.0 Peru 6800 9.71 138.0 Mexico 3800 5.43 51.4

*Cu reserves and production (mines and concentrates) in major countries [97].*

**(ten thousand tons)**

Poland 2800 4.00 Indonesia 2500 3.58

**Country Reserves/**

following Eqs. (7)–(9) represent the reduction processes for Cu ions:


*\* WHO; USEPA, United States Environmental Protection Agency; ISI, Indian Standard Institution; CPCB, Central Pollution Control Board; ICMR, Indian Council of Medical Research; BIS, Bureau of Indian Standards; EU, European limits via Directive 98/83/EC on the quality of water intended for human consumption; NM, the Moroccan official bulletin (NM 03.7.001).*

#### **Table 8.**

*Permissible limits of drinking water quality [104, 105, 109].*

that can be discharged into the public sewage system is 1 and 0.1 mg/L, respectively, for wastewater that can be discharged into public wastewater and which can be discharged into the recipient (surface and groundwater) [108].

#### *2.2.3.1.2.5 Heavy metal (namely Cr and Cu) removal techniques*

Faced with more and more stringent regulations, nowadays heavy metals are the environmental priority pollutants. In this regard, a wide range of removal technologies, such as chemical precipitation, ion exchange, adsorption, membrane filtration, and electrochemical, have been the subject of research nowadays.

In precipitation processes, chemicals react with heavy metal ions to form insoluble precipitates (such as hydroxide, sulfide, carbonates, etc.) by pH adjustment. The forming precipitates can be removed by physical means such as sedimentation, flotation, or filtration. **Table 9** reports some of the recent research in Cu(II) and Cr(VI) removal by chemical precipitation. It should be mentioned that Davarnejad and Panahi [110] reported that the adsorption method is considered to be the most common process used to remove different Cu ions from industrial wastewater. The efficiency of adsorption depends on many parameters; high surface area, pore size distribution, functional groups, and the polarity of the adsorbent determines the efficiency of adsorption process [66].

Many different cheap adsorbents have been developed and used for the removal of both Cu and Cr ions from metal-contaminated wastewater. Recently, activated carbons, agriculture byproducts, zeolites, and industrial wastes are widely employed to remove Cr(VI) from waters and industrial wastewaters [113]. Iftikhar et al. [114] investigated the use of rose waste biomass in Cr(III) and Cu(II) removal. In this study, the capacity of adsorption of Cu(II) and Cr(III) by rose biomass varies with temperature, and the maximum adsorption capacities of 55.79 and 67.34 mg/g, respectively, for Cu(II) and Cr(III) were found at 303 ± 1 K, with adsorption over 98% of Cu(II) and Cr(III). Natural zeolites are the most studied natural materials for the adsorption of heavy metals [115]. Ali and Yaşar [116] show the zeolite's high selectivity for Cu ions. In the same context, Barakat [117] studied the effect of pH on Cu adsorption and demonstrate that A4 zeolite is efficiently used to adsorb Cu(II), at natural and alkaline pH. At the same time, Francis et al. [115, 118] studied activated phosphate, zirconium phosphate, and calcined phosphate at 900°C, as net adsorbents to remove Cu(II). In addition, many researchers have reported that electrocoagulation (EC) is a suitable technology for heavy metal removal. The efficiency of this method in removing Cr(VI), Cu(II), and Ni from wastewater of an electroplating plant was investigated by Akbal and Camcidotless [119]. These authors achieved 100% Cu, 100% Cr, and 100% Ni removal at an EC time of 20 min with the use of Fe-Al electrode pair. **Table 10** resumes some of the electrochemical studies on Cr(VI) removal.

**59**

**3. Conclusion**

*Cu(II) and Cr(VI) removal electrochemical methods.*

**Table 10.**

*Pollution of Water Sources from Agricultural and Industrial Effluents: Special Attention…*

Cr(III) 5363 mg/L CaO and MgO 8.0 >99 Cr(VI) 30 mg/L FeSO4 8.7 >99

> Soda ash (Na2CO3), Sodium sulfide (Na2S)

**Precipitant Optimum** 

100 mg/L CaO 7–11 99.37–99.6

**Concentration pH Anode-cathode Removal Reference**

5 mg/L 7.0 Al alloy-Fe 98.2% [113] 1,000 mg/L 1.2 Carbon steel 100% [113] 100 mg/L 2 Fe-Cu 100% [113] 1,000 mg/L 4.5 Fe 100% [113] — 4 Al–Al 99% [113]

3–50 mg/L 2 Carbon felt 100% [113] 12 mg/L 3 CNTs 96% [113] 50 mg/L 0.5 Polyaniline ~70% [113]

coated Al3

nanoparticledecorated TiO2 nanotube array

1470 mg/L 1.84 Stainless steel 100 [112] 8 mg/L 2.0 Carbon aerogel 98.5 [69]

**pH**

H2S 3.0 100, >94, >92

10–11 >99

100% [113]

100% [113]

**Removal efficiency (%)**

Widespread pollution of surface and underground water resulted largely from increased pollutant discharges from industrial (specially the heavy metals), municipal, and agricultural sources (nutriments such as N and P), excessive water abstraction from the environment, and poor water resource management and enforcement of pollution control regulations. The preservation of water sources from pollutants, NO3ˉ, Cr and Cu, is a major concern, shared by all, public, industrial, scientific, researchers, and decision-makers. Over the past two decades, environmental regulations have become more stringent and require an improved quality of the treated effluents. Consequently, wide ranges of treatment technologies have been developed to remove agricultural and industrial pollutants. The

Electrochemical Cr(VI) Concentration pH Electrodes Removal

350 mg/L 0.7 Polypyrrole-

20 mg/L 11 Au

*DOI: http://dx.doi.org/10.5772/intechopen.86921*

**concentration**

0.018, 1.34, 2.3 mM

Cu(II), ZN 100 mg/L Lime (Ca(OH)2),

*Heavy metal removal using chemical precipitation [111, 112].*

**Species Initial metal** 

Cu(II), Zn(II), Cr(III), Pb(II)

Cu(II), Zn(II), Pb(II)

Electrocoagulation

Cr(VI)

**Table 9.**

*Pollution of Water Sources from Agricultural and Industrial Effluents: Special Attention… DOI: http://dx.doi.org/10.5772/intechopen.86921*


#### **Table 9.**

*Water Chemistry*

Cu permissible limit (mg/L)

*bulletin (NM 03.7.001).*

*\**

**Table 8.**

that can be discharged into the public sewage system is 1 and 0.1 mg/L, respectively, for wastewater that can be discharged into public wastewater and which can be

*WHO; USEPA, United States Environmental Protection Agency; ISI, Indian Standard Institution; CPCB, Central Pollution Control Board; ICMR, Indian Council of Medical Research; BIS, Bureau of Indian Standards; EU, European limits via Directive 98/83/EC on the quality of water intended for human consumption; NM, the Moroccan official* 

**International standard organizations WHO USEPA ISI CPCB ICMR BIS EU NM**

1.0 1.3 0.05 1.5 1.5 1.3 2 2

Faced with more and more stringent regulations, nowadays heavy metals are the environmental priority pollutants. In this regard, a wide range of removal technologies, such as chemical precipitation, ion exchange, adsorption, membrane filtra-

In precipitation processes, chemicals react with heavy metal ions to form insoluble precipitates (such as hydroxide, sulfide, carbonates, etc.) by pH adjustment. The forming precipitates can be removed by physical means such as sedimentation, flotation, or filtration. **Table 9** reports some of the recent research in Cu(II) and Cr(VI) removal by chemical precipitation. It should be mentioned that Davarnejad and Panahi [110] reported that the adsorption method is considered to be the most common process used to remove different Cu ions from industrial wastewater. The efficiency of adsorption depends on many parameters; high surface area, pore size distribution, functional groups, and the polarity of the adsorbent determines the

Many different cheap adsorbents have been developed and used for the removal

of both Cu and Cr ions from metal-contaminated wastewater. Recently, activated carbons, agriculture byproducts, zeolites, and industrial wastes are widely employed to remove Cr(VI) from waters and industrial wastewaters [113]. Iftikhar et al. [114] investigated the use of rose waste biomass in Cr(III) and Cu(II) removal. In this study, the capacity of adsorption of Cu(II) and Cr(III) by rose biomass varies with temperature, and the maximum adsorption capacities of 55.79 and 67.34 mg/g, respectively, for Cu(II) and Cr(III) were found at 303 ± 1 K, with adsorption over 98% of Cu(II) and Cr(III). Natural zeolites are the most studied natural materials for the adsorption of heavy metals [115]. Ali and Yaşar [116] show the zeolite's high selectivity for Cu ions. In the same context, Barakat [117] studied the effect of pH on Cu adsorption and demonstrate that A4 zeolite is efficiently used to adsorb Cu(II), at natural and alkaline pH. At the same time, Francis et al. [115, 118] studied activated phosphate, zirconium phosphate, and calcined phosphate at 900°C, as net adsorbents to remove Cu(II). In addition, many researchers have reported that electrocoagulation (EC) is a suitable technology for heavy metal removal. The efficiency of this method in removing Cr(VI), Cu(II), and Ni from wastewater of an electroplating plant was investigated by Akbal and Camcidotless [119]. These authors achieved 100% Cu, 100% Cr, and 100% Ni removal at an EC time of 20 min with the use of Fe-Al electrode pair. **Table 10** resumes some of the electrochemical

discharged into the recipient (surface and groundwater) [108].

*Permissible limits of drinking water quality [104, 105, 109].*

*2.2.3.1.2.5 Heavy metal (namely Cr and Cu) removal techniques*

efficiency of adsorption process [66].

tion, and electrochemical, have been the subject of research nowadays.

**58**

studies on Cr(VI) removal.

*Heavy metal removal using chemical precipitation [111, 112].*


**Table 10.**

*Cu(II) and Cr(VI) removal electrochemical methods.*
