Abstract
A new adsorbent of bentonite biochar composite (BRK) from natural bentonite and rice husk was synthesized for removal of ammonium (NH4+) from water. The preparation of the adsorbent consisted of a pyrolysis process at 400 °C and activation of biochar with KOH to obtain BRK. Various advanced techniques were applied to characterize the investigated adsorbent, including Fourier-transform infrared spectroscopy (FTIR), N2 adsorption analysis, scanning electron microscopy (SEM) integrated with Energy-Dispersive X-ray (EDX) Spectroscopy. The point of zero charge of BRK was 9.1. The pH solution strongly affected BRK’s adsorption capacity to NH4+ ions in the solution. The removal efficiencies of NH4+ were considerably diminished in the presence of coexisting cations (Na+, K+, Ca2+, and Mg2+). The Langmuir adsorption capacity of BRK for NH4+ was in the following order: 22.51 mg/g (10 oC) > 20.57 mg/g (30 oC) > 16.22 mg/g (50 oC). The kinetic experiments demonstrated that the adsorption equilibrium was achieved after 30 mins of contact. The ion-exchange was found to be the main adsorption mechanism for removing NH4+ by BRK. This study proved that BRK is a low-cost and sustainable adsorbent derived from natural bentonite and rice husk and it is advantageous for successfully removing NH4+ from water.