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The content of heavy metals extremely exceeds from the international level due to the anthropogenic activities brought from point and nonpoint sources, soil and water contamination occurs and agricultural products become unhealthy for human consumption. This study aimed to apply modified bentonite for adsorption of cadmium (Cd2+), copper (Cu2+) and nickel (Ni2+) from an aqueous phase. The natural Iranian bentonite was mixed with anionic surfactants, and sodium dodecyl sulfate (SDS) to produce modified bentonite. Batch experiments were performed in two individual and competitive solutions of Cd2+, Cu2+, and Ni2+(25–600 mg L–1) in the present of Na-B and SDS (10, 20, and 40 Mm). The results demonstrated that SDS modified bentonite (SDS-B) treatments enhanced the sorption capacity of natural adsorbents with increasing pH. The SDS-B in 40 mM is of more adsorption efficiency to adsorb Cd2+, Cu2+and Ni2+than are the other treatments. Among common and comprehensive isotherm models, Langmuir was well fitted to evaluate the data obtained from adsorption experiments. This is a novel study to compare the effect of modified bentonites into both single and comparative solution for heavy metal sorption. The maximum Langmuir adsorption capacity of Cd2+, Cu2+and Ni2+was 130.7, 94.4, and 83.06 as shown in SDS-B (40 mM) treatment. SDS-B treatments have the greatest affinity for Cd2+, but the Na-B adsorbs Ni2+more than the other cations. Using SDS-B showed remarkable gain in enhancing the adsorption efficiency compared to the Na-B in both individual and competitive batch experiments.

AbstractIn recent years, much attention has been focused on the use of material residues as low-cost adsorbents for the removal of heavy metal ions from aqueous solutions. Tea wastes are considered as a material that has abundantly been available and currently disposed as a solid waste and potentially could be suitable for the removal of heavy metals from aqueous solutions. The aim of this study is to investigate the removal of arsenic (As(V)) from aqueous solutions. Tested parameters include adsorbent dosage, pH, initial concentrations of arsenic, contact times, and temperatures. As(V) adsorption uptake was found to increase with increase in initial concentration, agitation time, adsorbent dosage, and solution temperature, whereas adsorption of As(V) was more favorable at acidic pH. The adsorption equilibrium data were best represented by the Freundlich and Langmuir isotherms. The adsorption kinetics was found to follow the pseudo-first-order kinetic model. Thermodynamic parameters such as standard enthalpy (ΔH), standard entropy (ΔS), and standard free energy (ΔG) were determined. The positive values of ΔGat different temperatures indicated that the nature of As(V) adsorption was not spontaneous. It can be concluded that tea wastes have a good ability to remove As(V) from aqueous solutions.