Modelling and Optimization of Simultaneous Removal of Ions (H2PO4-, NO3- and Cd2+) by Adsorption on Clay in Aqueous Solution by Using Response Surface Methodology

This paper deals with the modeling and optimization of the simultaneous elimination of dihydrogen phosphate nitrate and cadmium ions in an aqueous solution using adsorption on a smectite clay. Pollutant concentration and retention time are the two parameters studied. The experimental domains investigated are respectively from 20 to 100 mg.L-1 and from 8 to 16 hours. The tests were conducted with 3g of clay in a 25 mL mixture solution at pH 5. This study has been carried out with Response Surface Methodology (RSM), using NEMROD software. A central composite Design (CCD) was used first to establish a mathematical model that governs the process. The use of Derringer’s overall function of desirability permitted to establish optimal conditions of adsorption. Thus, maximum abatement rates both for each ion have been obtained when the pollutant concentration was 43 mg.L-1 with an adsorption duration of 15 hours. The results of the purification rates were 30.6 %, 68.1 %, and 69.07 %, respectively for nitrate, dihydrogenophosphate, and cadmium ions. It is noticeable that clay can be used as an adsorbent for wastewater depollution from many pollutants at a time.