A comprehensive study to understand removal efficiency for Cr6+ using magnetic and activated biochar through response surface methodology

This study highlights the advantageous effect of magnetic biochar (MLC) over conventional activated biochar (ALC) used for chromium adsorption from the aqueous solution. The synthesis of MLC was done using an invasive noxious weed “Lantana camara” with impregnation of iron chloride (FeCl3) on biochar surface at 25 °C. The optimum process parameters such as pH (3.01), adsorbent concentration (1.82 g/L), and adsorbate amount (161.23 mg/L) for the maximum chromium adsorption have been calculated using response surface methodology coupled with central composite design. Successful impregnation of iron on biochar with pre and post adsorption analysis has been confirmed using various characterization techniques viz. vibrating sample magnetometry (VSM), field emission scanning electron microscope (FESEM-EDX), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). Among various adsorption isotherms studied, Langmuir isotherm best fits the pseudo-second-order kinetic model for analysis of actual adsorption behavior of Cr6+ ions on ALC and MLC surfaces. Biochar MLC exhibited the maximum chromium adsorption capacity of 102.03 mg/g as compared to low chromium adsorption of 94.69 mg/g using conventional ALC biochar.