Eco-Friendly Adsorptive Removal of Chromium From Water and Wastewater by Nano Sodium Bentonite

Contamination of water sources with chromium has become a pervasive global problem due to its wide use in industry. In this research, low-cost commercial sodium bentonite and synthesized nano bentonite were used to remove chromium ions from aqueous solutions along with electro thermal atomic absorption spectroscopy (ETAAS) and Ultraviolet-Visible Spectrophotometry (UV-Vis) were used. The morphology of the bentonite samples was studied using XRD, FTIR and scanning electron microscope (SEM) analyzes. To screen the relative importance of variables, parameters including pH, adsorption time, amount of adsorbent, volume of desorption solvent and stirring speed were studied using the Plackett Burman Design (PBD) using the Minitab 20 software. In the following, optimization was performed by using the central composite design (CCD), and the responses were evaluated. The calibration curve was plotted by drawing the absorbance against standard concentration. The linear dynamic range of 0.003-100 μg L-1 (DLR) and the correlation coefficient (R2) of 0.999 were obtained for chromium. Limit of detection (LOD) and limit of quantification (LOQ) for chromium were obtained equal to 0.002 and 0.0039 μg L-1, respectively. The relative standard deviation (RSD) of 6.93% and the relative recovery for chromium in real samples were obtained in the range 96.041% to 103.445% for ETAAS method. The values of detection limit (LOD) and limit of quantification (LOQ) by UV-Vis method were 0.007 and 0.021 µg L-1 respectively, and the dynamic linear range was (DLR) 0.05-50.00 µg L-1 with a correlation coefficient (R2) 0.998. The relative standard deviation (RSD) was 14.27% and the relative recovery of this method in real samples was attained from 95.103% to 103.692%.