Adsorption of ammonium from wastewaters by an almond kernel derived biochar modified by potassium hydroxide or dolomite and activated by steam

Abstract

Excessive ammonium in wastewaters threatens the biodiversity of aqueous ecosystems and human health. Adsorption is an efficient, environmentally friendly and economically feasible process. Present work aimed to investigate the potential of almond kernel biochar modified by KOH or dolomite and activated by steam for ammonium adsorption. Structural, chemical and mineralogical analyses of the material before and after ammonium adsorption were conducted in order to examine the adsorption mechanisms. Experimental data were simulated by two isotherm models. Adsorption of ammonium reached equilibrium in 1 h, with a maximum removal efficiency 59.6% at initial concentration 50 mg/L and adsorption dose 4 g/L. By modification of biochar with KOH or dolomite, the maximum uptake of ammonium was improved, attaining values 73.2% and 67.3%, respectively. Freundlich model fitted the experimental results accurately (correlation coefficient 0.96). Maximum ammonium adsorption capacity of the material increased after KOH or dolomite modification up to 36.3 mg/g and 40.6 mg/g, respectively. The potential mechanisms could be surface complexation, coordination with aromatic π electrons of adsorbent and electrostatic interaction.

Keywords

• Adsorption
• Ammonium
• Steam activated biochar
• Potassium hydroxide and dolomite modified biochar
• Almond kernel