Adsorption of low-concentration ammonium onto vermiculite from hebei province, China

Vermiculite is a common layered silicate clay mineral which has good adsorption and ionexchange properties, and which is used to remove pollutants from groundwater. The adsorption by vermiculite from Heibei Province, China, of low-concentration ammonium in water was assessed here to evaluate the effects of adsorption time, particle size, adsorbent dose, pH, and temperature. Using Fouriertransform infrared spectroscopy, the concentration of NH4 at 1430 cm was evaluated after ammonium was adsorbed by vermiculite. Based on Langmuir-model analysis, the adsorption capacity ofthe Chinese vermiculite (in the particle-size range 0.025-0.075 mm) for ammonium was 18 mg/g after 3 h of equilibration. Optimal adsorption occurred at pH 6-7 and 60°, which is different from that at high ammonium concentrations. Smaller particle-size fractions showed greater degrees of adsorption. Increase in Mg , K , or Na concentrations influenced ammonium adsorption and, therefore, indicated that cation exchange was the mechanism for ammonium uptake from low-concentration solutions