Response surface modeling for Pb(II) removal from alcoholic beverages using natural clay: Process optimization with box–behnken experimental design and determination by electrothermal AAS

A three-level four-factor Box–Behnken experimental design (BBD) combined with response surface modeling (RSM) was used for the optimization and modeling of Pb(II) adsorption from alcoholic beverages onto natural clay. The BBD method was chosen as the statistical prediction method to reduce the experimental numbers which saves time and chemicals and reduce analysis cost. Various independent process variables including solution pH (X1: 3.0– 7.0), contact time (X2: 2–60 min), adsorbent dosage (X3: 0.01-0.1 g), and agitation speed (X4: 50–150 rpm) were optimized. The optimal conditions used for Pb(II) removal were pH of 5.3, contact time 38.9 minutes, 0.071 g adsorbent dosage, and 98.7 rpm agitation speed, resulting in a maximum removal efficiency of 120 mg g-1. Pb was determined by electrothermal AAS. The significance of the independent variables and their interactions were tested by means of the analysis of variance (ANOVA) and are based on the ANOVA statistical value. The adsorption of Pb(II) onto clay was found to be highly significant with very low probability (p) values (<0.001). These results were justified by the relatively high correlation coefficients (R2 = 0.9965, R2 adj = 0.9930, and R2 Pred= 0.9819) of the statistical prediction. FTIR analysis confirmed major participation of amide, amines, ketones, including the primary alcohol groups, during Pb(II) biosorption. Clay was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM), coupled with energy dispersive X-Ray (EDX). The proposed adsorption process efficiently removes Pb(II) present in various aqueous media and can be used for industrial wastewater or drinks.