Influence of process parameters on sorption capacity of microwave activated biosorbents for urea recovery from human urine: a comparative study

Abstract

AbstractThe present investigation elicits a comparative study for recovering urea from human urea via adsorption onto three biosorbents: Microwave Activated Carbonized Bamboo Shoots (MACBS), Walnut Shells (MACWS) and Coconut Shells (MACCS). The rate of sorption was investigated under different process parameters including initial sorbate concentration, amount of sorbent, temperature and agitation speed, and further, sorption capacity of MACBS, MACWS and MACCS was compared. Batch results indicated that urea uptake capacity increased with an increase in sorbate concentration and a decrease in sorbent loading and temperature. The experimental data were tested against the Langmuir, Freundlich, Tempkin, Flory–Huggins and Dubinin–Radushkevich (D‐R) isotherms with the D‐R model being a good fit for MACBS and MACCS and the Freundlich model for MACWS. Kinetic studies were performed to understand the order and rate of the sorption process. While pseudo‐second‐order kinetic model fits best for MACBS and MACWS, pseudo‐first order was followed by MACCS. Based on the urea sorption capacity, the following order of suitability of precursors for activated carbon preparation was established: MACBS > MACCS > MACWS. This study illustrates the suitability of biomass‐based precursors for activated carbon preparation and nutrient recovery from wastewater streams like human urine for subsequent use as fertilizers on agricultural land. © 2015 Curtin University of Technology and John Wiley & Sons, Ltd.