Equilibrium and Kinetics of Ammonia Nitrogen Biosorption from Wastewater by Spent Grains

This study focused on the characteristics of the removal of ammonia nitrogen in wastewater with spent grains, a by-product of the brewing process. The influences of density of NaCl solution, pH, contact time and initial ammonia concentration were investigated in batch experiments. The largest removal was obtained at pH 8 in 30 min by 20 g/L spent grains modified by 5% NaCl solution when the initial ammonia concentration 400 mg/L. The equilibrium process was described well by the Langmuir isotherm model with maximum sorption capacities of 132.8 mg/g of ammonia on modified spent grains (MSGs). Good correlation coefficient was obtained for the pseudo second-order kinetic model. In the end, metallurgical wastewater containing high concentration of ammonia nitrogen was treated by MSGs. With the initial ammonia concentration 4500 mg/L at pH 8, ammonia was reduced to 310 mg/L in 40 min by 40 g/L MSGs. It could be proposed that 5% NaCl MSGs is an effective adsorbent for the removal of ammonia nitrogen from wastewater.