**6. Adsorption of pesticides and herbicides**

Pesticides and herbicides, intentionally released into the environment, are ubiquitous in aquatic systems; they are often detected at low levels and commonly occur in the form of complex mixtures [64-65]. Leaching of chemical fertilizers and pesticides, applied to agricul‐ tural and forest land, is one of the main reasons for organic pollution in several water streams. Pesticides and herbicides are harmful to life because of their toxicity, carcinogenici‐ ty and mutagenicity [66]. Therefore toxicity of pesticides and their degradation products is making these chemical substances a potential hazard by contaminating the environment. They have raised serious concerns about aquatic ecosystem and human health because of the long-term accumulation of their single and/or combined toxicological effects [67]. The contamination of ground water,surface water and soils, by pesticides and herbicides are cur‐ rently a significant concern, and this because of increasing use of pesticides in agriculture, and domestic activities [68].

Other modified polymer adsorbent was used in herbicides treatment, porous polymeric ad‐ sorbents were used for the adsorption of herbicides (alachlor, amitrole, trifluralin and prom‐ etryn ) from liquid solution. Two adsorbent resins were investigated, the highly hydrophobic Amberlite XAD-4 (polystyrene–divinylbenzene copolymer) and the functional‐ ized more hydrophilic XAD-7 (nonionic aliphatic acrylic polymer). The adsorption were sus‐

Adsorption Technique for the Removal of Organic Pollutants from Water and Wastewater

http://dx.doi.org/10.5772/54048

177

Other adsorbent used widely for the removal of pesticides is activated carbon. Activated carbons (ACs) prepared from agricultural and industrial wastes were used for the removal of pesticides from polluted water. Activated carbons produced from agricultural residues (olive kernel, corn cobs, rapeseed stalks and soya stalks) via physical steam activation were tested for the removal of Bromopropylate (BP) pesticide from water. The results show maxi‐ mum adsorption capacity( qm) of the pesticide on adsorbents (ACs) prepared from corn cob, olive kernel, soya stalks and rapeseed stalks at values 7.9x 10\_2,12.3 x 10\_2, 11.6 x 10\_2 and 18.9 x 10\_2 mmol/L, respectively. The BP removal from water achieved in this study was 90–100%

Ayranci and Hoda [76] studied the adsorption of pesticides,pesticides ametryn [2- (ethyla‐ mino)-4-isopropylamino-6-methyl-thio-s-triazine], aldicarb (2-methyl-2-(methylthio) propio‐ naldehyde o-methylcarbamoyloxime], diuron [N-(3,4-dichlorophenyl)- N,N-dimethyl urea] and dinoseb [2-(sec-butyl)- 4,6-dinitrophenol], from aqueous solution onto high specific area activated carbon-cloth adsorbent (ACC ) and found that the maximum adsorption capacity of ACC for ametryn, diuron, dinose and aldicarb were 354.61,421.58, 301.84 and 213.06

Djilani et al. [77] developed new activated carbon adsorbents from lignocellulosic wastes of vegetable origin (coffee grounds (CG), melon seeds (MS) and orange peels (OP)). The ad‐ sorption efficiency of these new adsorbents was tested with organic pollutants: o-nitrophe‐ nol and p-nitrotoluene. The elimination ratio obtained with new adsorbents was in the range from 70% to 90%. The time necessary to attain the adsorption equilibrium was be‐

The ability of MgAl layered double hydroxides (LDHs) and their calcined products to ad‐ sorb besticides contaminants, 2,4-dinitrophenol (DNP) and 2-methyl-4,6-dinitrophenol (DNOC) from water was assessed. Adsorption tests were conducted on LDHs with variable Mg/Al ratios (and variable layer charge), pH values, contact times and initial pesticide con‐ centrations to identify the optimum conditions for the intended purpose. All adsorbents ex‐ cept the carbonate-containing hydrotalcite possessed a very high adsorption capacity for both contaminants. As noted above, the adsorption of the pesticides on the calcined LDHs

Activated carbon prepared from banana stalk by potassium hydroxide (KOH) and carbon dioxide (CO2) activation (BSAC ) was explored for its ability to remove the pesticides, 2,4 dichlorophenoxyacetic acid (2,4-D) and bentazon. The percent removal efficiency of 2,4-D decreased from 98.4 to 85.4% as the 2,4-D initial concentration increased from 50 to 300 mg L −1. For bentazon, the percent removal efficiency decreased from 96.5 to 61.6% as the bentazon

sccufuly at pH 6.5 [74].

for all ACs [75].

mg/g, respectively.

tween 75 and 135 min.

was only 25–40% [78]

Among newly developed pesticides, organophosphorous pesticides are most commonly used. This class of chemicals is divided into several forms; however the two most common forms are phosphates and phosphorothionates. Methyl parathion (O,O-dimethyl O-4-nitro‐ phenyl phosphorothioate) is a class I insecticide. Once methyl parathion introduced into the environment from spraying on crops, droplets of methyl parathion in the air fall on soil, plants or water. While most of the methyl parathion will stay in the areas where it is ap‐ plied, some can move to areas away from where it was applied by rain, fog and wind [69].

Modified polymer adsorbents were prepared for the removal of organic pollutants from wa‐ ter and wastewater. Adsorption of organic pollutants using cyclodextrin-based polymer (CDPs) as adsorbent, is an efficient technique with the advantages of specific affinity, low cost and simple design [65, 70-71]. Cyclodextrin polymers (CDPs) can be synthesized using cyclodextrin (CD) as complex molecule and polyfunctional substance (e.g., epichlorohydrin (EPI)) as cross-linking agent.Though a number of CDPs with various structures and proper‐ ties have been developed [72,73], it is still ambiguous how CDP properties affect adsorption affinity toward organic contaminants, particularly mixed pollutants. Liu et al. [66] illustrat‐ ed the cross-linked structure of cyclodextrin polymer and related adsorption mechanisms in Scheme ( 1 ).

**Scheme 1.** Cross-linked structure of cyclodextrin polymer and related adsorption mechanisms, from Liu et al. [66].

Other modified polymer adsorbent was used in herbicides treatment, porous polymeric ad‐ sorbents were used for the adsorption of herbicides (alachlor, amitrole, trifluralin and prom‐ etryn ) from liquid solution. Two adsorbent resins were investigated, the highly hydrophobic Amberlite XAD-4 (polystyrene–divinylbenzene copolymer) and the functional‐ ized more hydrophilic XAD-7 (nonionic aliphatic acrylic polymer). The adsorption were sus‐ sccufuly at pH 6.5 [74].

the long-term accumulation of their single and/or combined toxicological effects [67]. The contamination of ground water,surface water and soils, by pesticides and herbicides are cur‐ rently a significant concern, and this because of increasing use of pesticides in agriculture,

Among newly developed pesticides, organophosphorous pesticides are most commonly used. This class of chemicals is divided into several forms; however the two most common forms are phosphates and phosphorothionates. Methyl parathion (O,O-dimethyl O-4-nitro‐ phenyl phosphorothioate) is a class I insecticide. Once methyl parathion introduced into the environment from spraying on crops, droplets of methyl parathion in the air fall on soil, plants or water. While most of the methyl parathion will stay in the areas where it is ap‐ plied, some can move to areas away from where it was applied by rain, fog and wind [69].

Modified polymer adsorbents were prepared for the removal of organic pollutants from wa‐ ter and wastewater. Adsorption of organic pollutants using cyclodextrin-based polymer (CDPs) as adsorbent, is an efficient technique with the advantages of specific affinity, low cost and simple design [65, 70-71]. Cyclodextrin polymers (CDPs) can be synthesized using cyclodextrin (CD) as complex molecule and polyfunctional substance (e.g., epichlorohydrin (EPI)) as cross-linking agent.Though a number of CDPs with various structures and proper‐ ties have been developed [72,73], it is still ambiguous how CDP properties affect adsorption affinity toward organic contaminants, particularly mixed pollutants. Liu et al. [66] illustrat‐ ed the cross-linked structure of cyclodextrin polymer and related adsorption mechanisms in

**Scheme 1.** Cross-linked structure of cyclodextrin polymer and related adsorption mechanisms, from Liu et al. [66].

and domestic activities [68].

176 Organic Pollutants - Monitoring, Risk and Treatment

Scheme ( 1 ).

Other adsorbent used widely for the removal of pesticides is activated carbon. Activated carbons (ACs) prepared from agricultural and industrial wastes were used for the removal of pesticides from polluted water. Activated carbons produced from agricultural residues (olive kernel, corn cobs, rapeseed stalks and soya stalks) via physical steam activation were tested for the removal of Bromopropylate (BP) pesticide from water. The results show maxi‐ mum adsorption capacity( qm) of the pesticide on adsorbents (ACs) prepared from corn cob, olive kernel, soya stalks and rapeseed stalks at values 7.9x 10\_2,12.3 x 10\_2, 11.6 x 10\_2 and 18.9 x 10\_2 mmol/L, respectively. The BP removal from water achieved in this study was 90–100% for all ACs [75].

Ayranci and Hoda [76] studied the adsorption of pesticides,pesticides ametryn [2- (ethyla‐ mino)-4-isopropylamino-6-methyl-thio-s-triazine], aldicarb (2-methyl-2-(methylthio) propio‐ naldehyde o-methylcarbamoyloxime], diuron [N-(3,4-dichlorophenyl)- N,N-dimethyl urea] and dinoseb [2-(sec-butyl)- 4,6-dinitrophenol], from aqueous solution onto high specific area activated carbon-cloth adsorbent (ACC ) and found that the maximum adsorption capacity of ACC for ametryn, diuron, dinose and aldicarb were 354.61,421.58, 301.84 and 213.06 mg/g, respectively.

Djilani et al. [77] developed new activated carbon adsorbents from lignocellulosic wastes of vegetable origin (coffee grounds (CG), melon seeds (MS) and orange peels (OP)). The ad‐ sorption efficiency of these new adsorbents was tested with organic pollutants: o-nitrophe‐ nol and p-nitrotoluene. The elimination ratio obtained with new adsorbents was in the range from 70% to 90%. The time necessary to attain the adsorption equilibrium was be‐ tween 75 and 135 min.

The ability of MgAl layered double hydroxides (LDHs) and their calcined products to ad‐ sorb besticides contaminants, 2,4-dinitrophenol (DNP) and 2-methyl-4,6-dinitrophenol (DNOC) from water was assessed. Adsorption tests were conducted on LDHs with variable Mg/Al ratios (and variable layer charge), pH values, contact times and initial pesticide con‐ centrations to identify the optimum conditions for the intended purpose. All adsorbents ex‐ cept the carbonate-containing hydrotalcite possessed a very high adsorption capacity for both contaminants. As noted above, the adsorption of the pesticides on the calcined LDHs was only 25–40% [78]

Activated carbon prepared from banana stalk by potassium hydroxide (KOH) and carbon dioxide (CO2) activation (BSAC ) was explored for its ability to remove the pesticides, 2,4 dichlorophenoxyacetic acid (2,4-D) and bentazon. The percent removal efficiency of 2,4-D decreased from 98.4 to 85.4% as the 2,4-D initial concentration increased from 50 to 300 mg L −1. For bentazon, the percent removal efficiency decreased from 96.5 to 61.6% as the bentazon

initial concentration increased from 25 to 250 mg L−1. Therefore, the adsorption of 2,4-D and bentazon by BSAC has strong dependence on the initial concentration of the pesticides. Maximum adsorption capacity (qe) for 2,4-dichlorophenoxyacetic acid (2,4-D) were 168.03 mg g−1, and for bentazon 100.95 mg g−1 [79]

weeks. The adsorbent had good adsorption capability to dieldrin, which was indicated by a residual dieldrin concentration of 0.204 μgL−1. The removal efficiency of the composite ad‐ sorbent was higher than the traditional activated carbon adsorbent [83]. Essa et al. [84] stud‐ ied the potential of chemical activated date pits as an adsorbent. The date pits were impregnated with 70% phosphoric acid followed by thermal treatment between 300 to 700°C. The effects of activation temperature and acid concentration on pore surface area de‐ velopment were studied. Samples prepared at 500°C showed a specific area of 1319 m<sup>2</sup>

Five commercially available types of activated carbon (GAC 1240, GCN 1240, RB 1, pK 1-3, ROW 0.8 SUPRA )are prepared and used to remove organic chlorinated compounds from wastewater of a chemical plant. The various types of activated carbon were tested on the ba‐ sis of Freundlich adsorption isotherms for 14 pure organic chlorinated compounds, of mo‐ lecular weight ranging from that of dichloromethane (MW ¼ 84.93 g mol-1) to hexachlorobenzene (MW ¼ 284.78 g mol-1). The best adsorbent (GAC 1240 granulated acti‐ vated carbon ) was selected and used in a laboratory fixed bed column to assess its removal efficiency with respect to the tested organic chlorinated compounds. Removal efficiency was

**Substance Precenage of adsorption efficiency (%)**

**Table 3.** Removal efficiency (%) of chlorinated compounds from wastewater by five commercially available types of

Antibiotic considered as one of the pharmacological organic pollutants. Choi et al. [86] investi‐ gated the treatment of seven tetracycline classes of antibiotic (TAs) from raw waters (synthetic and river) using coagulation and granular activated carbon (GAC) filtration. Their results ended to that both coagulation and GAC filtration were effective for the removal of TAs, and the

tivated carbon sample were compared to a commercial sample (Filtrasorb-400).

/g. Aqueous phenol adsorption trends using the local ac‐

Adsorption Technique for the Removal of Organic Pollutants from Water and Wastewater

98.3 98.8 99.0 99.0 82.8 94.7 86.3 91.6 87.3 94.2 99.2 90.5 99.4 95.1

and total pore volume of 0.785 cm3

always higher than 90% (Table 3) [85]

activated carbon, from Pavonia et al [85]

Dichloromethane Trichloromethane 1,1,1- Trichloromethane Carbon tetrachloride 1,2-Dichloroethane Trichloroethylene 1,1,2- Trichloroethane Tetrachloroethylene 1,1,1,2- Tetrachloroethane Trans 1,4-dichloro-2-butene 1,2,4-Trichlorobenzene 1,2,3-Trichlorobenzene Hexachloro-1,3-butadiene Hexachlorobenzene

/g

179

http://dx.doi.org/10.5772/54048

In the other study for using activated carbon as adsorbent, magnetic and graphitic carbon nanostructures was used for the removal of a pesticide (2,4-dichlorophenoxyacetic acid) from aqueous solution.The magnetic and graphitic carbon nanostructures as adsorbents were prepared from two different biomasses, cotton and filter paper. The resultant adsorb‐ ents were characterized with TEM and N2 adsorption–desorption methods. The adsorption capacities for the prepared adsorbents from filter paper and cotton are about 77 and 33 mg/g, respectively [80].

Chemically and thermally treated watermelon peels (TWMP) have been utilized for the re‐ moval of methyl parathion (MP) pesticide from water. The effect of process variables such as pH of solution, shaking speed, shaking time, adsorbent dose, concentration of solution and temperature have been optimized. Maximum adsorption (99±1%) was achieved for (0.38– 3.80)×10−4 mol dm−3 of MP solution, using 0.1 g of adsorbent in 20 ml of solution for 60 min agitation time at pH 6. The developed adsorption method has been employed to surface wa‐ ter samples with percent removal 99%±1 [81].
