Adsorption of ammonium nitrogen and phosphate onto basanite and evaluation of toxicity

Pure and surface-modified basanites (SMBs) were investigated for treatment of nutrients such as ammonium nitrogen and phosphate in aqueous solution. Basanite is a volcanic rock with a large specific surface area due to its vesicular structure. Moreover, basanite contains silica and calcium, promoting surface fixation of hydroxyl groups. The equilibrium adsorption of ammonium nitrogen and phosphate in aqueous solutions by four types of basanite adsorbents was evaluated. The adsorption isotherms were well described by a Langmuir adsorption model. Among the adsorbents, the SMB prepared by reaction with 20 % sodium hydroxide had the highest adsorption capacities for ammonium nitrogen (5.38 mg/g) and phosphate (19.74 mg/g). In addition, cytotoxicity of the pure basanite and SMBs was also evaluated. None of the basanite adsorbents showed cytotoxic effects to human cells at concentration in effluents. Thus, the SMBs were found to be promising materials for removal of ammonium nitrogen and phosphate from sewage.