Biochar from microwave pyrolysis of rice husk for tertiary wastewater treatment and soil nourishment

Abstract

The present study investigated the potential tertiary treatment of wastewater by adsorption using rice husk biochar (RHC) obtained from microwave pyrolysis of rice husk. Adsorption experiments with RHC indicated phosphate and nitrate adsorption of 65% and 75% respectively. The adsorption kinetics indicated pseudo-second-order adsorption model for adsorption of nutrients on biochar with an R2 value more than 0.98. In addition, the Langmuir-Freundlich isotherm was observed to represent the adsorption of phosphate on RHC, whereas adsorption data of nitrate depicted Langmuir isotherm followed by Temkin and Dubinin-Radushkevich isotherms. The maximum phosphate and nitrate adsorption capacity were 71 mg/kg and 497 mg/kg respectively using Langmuir isotherm model. The desorption study indicated a release of 96.6% and 44.4% of adsorbed phosphate and nitrate, respectively. Hence, from 1 kg of nutrient loaded RHC about 68 mg of phosphate and 220 mg of nitrate can be extracted for land application. � 2019