A facile technique to prepare MgO-biochar nanocomposites for cationic and anionic nutrient removal

Abstract

The removal of NH4+ and PO43− from water using adsorbents produced from rice husk and corn cob byproducts was examined. The synthesis of MgO-biochar nanocomposites was conducted by magnesium activation under nitrogen atmosphere at 400 °C and 500 °C. The characterization of different materials was performed using various modern instruments such as XPS, SEM, EDS, XRD, FT-IR, BET…The comparison between modified and unmodified biochars for removing NH4+ and PO43− from water and the impact of different parameters on adsorption capacity of obtained materials were also performed. The results showed that the activation of biochar by magnesium led to changes in surface areas, pore volume, surface charge, and chemical properties of biochars and to increases in NH4+ and PO43− adsorption capacity. The adsorption of NH4+ and PO43− onto biochar-based nanocomposites followed both chemisorption and physisorption, were spontaneous, and endothermic. The NH4+ maximum uptake calculated according to Langmuir model were 21.32 mg/g for RMgN500 and 16.31 mg/g for CMgN500 while the PO43− maximum uptake were 117.77 mg/g and 52.24 mg/g for of RMgN500 and CMgN500, respectively. The desorption and recyclability of the RMgN500 and CMgN500 were very effective by using 0.5 M NaOH solution for PO43− and diluted HCl solutions for NH4+. This approach of synthesizing MgO nanoparticles impregnated in biochar matrix provided new opportunities in developing low-cost and highly efficient adsorbent to removal and recovery of NH4+ and PO43− from water.