Three bentonite modified with organic surfactants were used to remove 2, 4-dichlorophenol (2, 4-DCP) from aqueous solution. Of the three bentonites studied, DK3, modified with octadecyl dimethyl benzyl ammonium chloride (ODBAC), was found to be most effective and the conditions affecting batch adsorption of 2, 4-DCP were evaluated. The adsorption data fit the Langmuir isotherm model well predicting a high adsorption capacity of 281.8mg/g at 30℃. A pseudo-second-order model was used to calculate the corresponding rate constant of 10.35mg/g min−1 at 30℃. Thermodynamic parameters demonstrated that the overall adsorption process was exothermic and spontaneous. Furthermore, DK3 was characterized by scanning electronic microscopy (SEM), specific surface area (SSA), X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) spectrometer, which provided evidence of morphological properties and the adsorption of 2, 4-DCP onto DK3. Finally, DK3 was used to remove>92% of 2, 4-DCP from industrial wastewater having an initial concentration of 10.0mg/L.

In this study, organobentonites were prepared by modification of bentonite with various cationic surfactants, and were used to remove As(V) and As(III) from aqueous solution. The results showed that the adsorption capacities of bentonite modified with octadecyl benzyl dimethyl ammonium (SMB3) were 0.288 mg/g for As(V) and 0.102 mg/g for As(III), which were much higher compared to 0.043 and 0.036 mg/g of un-modified bentonite (UB). The adsorption kinetics were fitted well with the pseudosecond-order model with rate constants of 46.7×10−3 g/mg h for As(V) and 3.1×10−3 g/mg h for As(III), respectively. The maximum adsorption capacity of As(V) derived from the Langmuir equation reached as high as 1.48 mg/g, while the maximum adsorption capacity of As(III) was 0.82 mg/g. The adsorption of As(V) and As(III) was strongly dependent on solution pH. Addition of anions did not impact on As(III) adsorption, while they clearly suppressed adsorption of As(V). In addition, this study also showed that desorbed rates were 74.61% for As(V) and 30.32% for As(III), respectively, after regeneration of SMB3 in 0.1M HCl solution. Furthermore, in order to interpret the proposed absorption mechanism, both SMB3 andUBwere extensively characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses.

In this study, organobentonites were prepared by modification of bentonite with various cationic surfactants, and were used to remove As (V) and As (III) from aqueous solution. The results showed that the adsorption capacities of bentonite modified with octadecyl benzyl dimethyl ammonium (SMB3) were 0.288 mg/g for As (V) and 0.102 mg/g for As (III), which were much higher compared to 0.043 and 0.036 mg/g of un-modified bentonite (UB). The adsorption kinetics were fitted well with the pseudosecond-order model with rate constants of 46.7×10−3g/mg h for As (V) and 3.1×10−3g/mg h for As (III), respectively. The maximum adsorption capacity of As (V) derived from the Langmuir equation reached as high as 1.48 mg/g, while the maximum adsorption capacity of As (III) was 0.82mg/g. The adsorption of As (V) and As (III) was strongly dependent on solution pH. Addition of anions did not impact on As (III) adsorption, while they clearly suppressed adsorption of As (V). In addition, this study also showed that desorbed rates were 74.61% for As (V) and 30.32% for As (III), respectively, after regeneration of SMB3 in 0.1M HCl solution. Furthermore, in order to interpret the proposed absorption mechanism, both SMB3 andUBwere extensively characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses.

Nanoscale zero-valent iron (nZVI) used to remediate contaminated groundwater is limited due its lack of durability and mechanical strength. To address these issues, synthesized kaolin supported nanoscale zerovalent iron (K-nZVI) was used to remove Pb (II) ion from aqueous solution. This study has demonstrated that synthesized K-nZVI was efficient in removing Pb (II) from aqueous solution containing 500mgL−1 of Pb (II), where 90.1% of Pb (II) was removed within 60 min using 5g L−1 of K-nZVI having a nZVI mass fraction of 20% at pH 5-6. Ni (II) and Cd (II), as co-existent ions, were also removed by the synthesized KnZVI. This however had little effect on the removal of Pb (II) from solution. The synthesized K-nZVI could be reused more than 5 times when applied to remove Pb (II) from solution with concentrations of 50mgL−1. Additionally, synthesized K-nZVI was efficient in removing Pb (II) (98.8%) and total Cr (99.8%) from an electroplating wastewater, indicating that the synthesized nZVI is a potential remediation material when used for the treatment of electroplating wastewater containing metal ions.

Modified kaolinite clay with 25% (w/w) aluminium sulphate and unmodified kaolin were investigated as adsorbents to remove Pb (II) from aqueous solution. The results show that amount of Pb (II) adsorbed onto modified kaolin (20mg/g) was more than 4.5-fold than that adsorbed onto unmodified kaolin (4.2mg/g) under the optimized condition. In addition, the linear Langmuir and Freundlich models were used to describe equilibrium isotherm. It is observed that the data from both adsorbents fitted well to the Langmuir isotherm. The kinetic adsorption of modified and unmodified kaolinite clay fitted well to the pseudo-second-order model. Furthermore, both modified and unmodified kaolinite claywere characterized by X-ray diffraction, Fourier transform infrared (FT-IR) and scanning electron microscope (SEM). Finally, both modified and unmodified kaolinite clay were used to remove metal ions from real wastewater, and results show that higher amount of Pb (II) (the concentration reduced from178 to 27.5 mg/L) and other metal ions were removed by modified kaolinite clay compared with using unmodified adsorbent (the concentration reduced from 178 to 168 mg/L).