Optimization of arsenic ions adsorption and removal from hospitals wastewater by nano-bentonite using central composite design

Abstract

Nano-bentonite was prepared from Iraqi bentonite clay by the co-precipitation method and the adsorption technique was used under many factors to determine the adsorption capacity (q) and removal% of arsenic ions (As) from the hospital's wastewater. The optimization process was conducted to choose the optimal parameters for adsorption and removal of arsenic by applying the central composite design (CCD) to form a surface response with three levels and three central points. Three operational factors were optimized of pH (5.5), bentonite dose (100 mg/L), and contact time (5 min), as well as developing the regression quadratic equations to assess the important models for the arsenate adsorbing and removing which dependent on the correlation factor (R2) that was (q = 0.9998) and (removal% = 0.9709), the adsorption isotherm results were fit well with the Langmuir model (R2 = 0.972), and the adsorption kinetics results were perfect with the second model (R2 = 0.951). We conclude that bentonite clay is a good adsorbent that can be used in the processes of removing toxic ions from water.