Could organoclay be used as a promising natural adsorbent for efficient and cost-effective dye wastewater treatment?

Abstract

There is an urgent need for developing eco-friendly adsorbents for dye wastewater treatment with high efficiency and low cost. Meanwhile, organoclay has received an increasing attention as a natural adsorbent for dye removal. However, no comprehensive investigation has been conducted to evaluate the feasibility of this approach in terms of operation cost and removal efficiency. In this research, we intend to answer this question: could organoclay be used as an efficient and cost-effective approach for dye wastewater treatment? In line with that, after characterization of the Na-bentonite and modified clay by using SEM, EDX, FTIR and XRD, the performance of the organoclay was optimized in terms of AO7 dye removal efficiency and adsorption cost using response surface methods (RSM). Then, the organoclay performance was compared with other typical adsorbents activated carbon and chitosan. The characterization results proved that Na-bentonite was successfully modified by CTAB. According to RSM results, the maximum dye removal of 95% and the minimum adsorption cost of 0.009 $/g were achieved under optimum conditions of: pH: 5, AO7 concentration: 56 mg/L, contact time: 53 min and organoclay dosage: 0.8 g/L. While, in the case of other adsorbents of Na-bentonite, chitosan and activated carbon the maximum removal of 11%, 84% and 92% were achieved with 0.0136, 0.0324 and 0.1011 $/g, respectively. The adsorption kinetics and isotherms analyses revealed that the experimental data fitted well with the pseudo-second-order (R2 = 0.993) and Langmuir (R2 = 0.988). This study proved that organoclay can be used as a promising adsorbent for dye removal with low cost and high removal efficiency.