Ammonium removal by alkaline-activated coconut coir from synthetic and ground waters

High ammonium concentration in groundwater in Viet Nam is a threaten consequence to Vietnamese people in suburban and rural areas. Coconut coir is an economic waste of Viet Nam's agriculture with million tons generated every year. In this work, NaOH treatment of raw coconut coir (RCC) was implemented to obtain activated biomaterial (NaACC) for evaluation of ammonium adsorption from synthetic and ground waters. First, the effects of adsorbent dosage, initial ammonium concentration, reaction time, temperature on adsorption performance, adsorption isotherm, and kinetics for ammonium-contained synthetic water were investigated. Second, the ammonium adsorption performance of NaACC from a natural groundwater was also evaluated. The removal efficiencies of ammonium were 49.5, 60.6, and 66.7% with maximum adsorption capacities of 0.51, 0.67, and 0.74 mg/g at temperatures of 30, 40, and 50 degrees C, respectively, at pH 7.0, NaACC dose 40 g/L, initial ammonium concentration 40 mg/L, and reaction time 144 h. The NaACC displayed the best ammonium adsorption following Langmuir isotherm (R-2 = 0.9990) and pseudo-second-order kinetic model (R-2 = 0.9989). The NaACC also exhibited a good ammonium adsorption in natural groundwater with removal efficiency and adsorption capacity of 82.6% and 0.77 mg/g, respectively. Particularly, NaACC can be regenerated up to three cycles for consecutive adsorption of ammonium in groundwater without loss of its adsorptive performance. Therefore, NaACC derived from agricultural wastes was a potential biomaterial for cleaning ammonium from contaminated groundwater.