Removal of nitrate and phosphate from aqueous solutions using bioadsorbents derived from agro-industrial wastes of rice husk and corn stalk

Abstract The main objective of this study was to evaluate the adsorption efficiency for removing nitrate and phosphate in an aqueous solution using adsorbents derived from rice husks and corn stalks. Five adsorbents were used: untreated rice husk (RH), raw corn stalk (CS), rice husk biochar (RHB), corn stalk biochar (CSB), and a rice husk biochar chemically modified with magnesium (RHB-Mg). The influence of operational variables (temperature, pH, adsorbent dose, and initial concentration) on individual and competitive adsorption of nitrate and phosphate was studied together with adsorption equilibrium and kinetics. The results showed that the best adsorbent was RHB-Mg, with maximum adsorption capacities of 111.10 mg/g for phosphate and 35.11 mg/g for nitrate, determined from Langmuir isotherm. Competitive adsorption of nitrate and phosphate was favorable using RHB-Mg, demonstrating that RHB-Mg could be used to remove these nutrients from wastewater.