Removal of Ammonium Ions from Fellmongery Effluent by Zeolite

Abstract

The introduction of the Resource Management Act in 1991 in New Zealand enforces statutory requirements for the disposal of farm and industrial wastewaters in ways that minimize environmental impacts. Wastewaters often contain high concentrations of ammonium (), phosphate () and potassium (K+) ions, and in some cases heavy metals. Zeolite is a naturally occurring, porous and electrically-charged alumino–silicate mineral, which can be used to adsorb cation and anion contaminants from wastewater. Zeolites of New Zealand origin were obtained from New Zealand Resource Refineries Ltd. and evaluated for their effectiveness to remove ions from a fellmongery wastewater stream. The natural zeolites were of clinoptilolite species and had high cation exchange capacity (CEC) (>100 cmol kg−1), which after treatment with alkali solutions increased by up to 74%. The CEC of the zeolites indicated that these samples can hold a potential maximum of 18.7 to 20.1 g zeolite. The adsorption of ions by the zeolites increased with increasing ion concentration in the fellmongery wastewater. The presence of other cations in the fellmongery wastewater apparently interfered with ion adsorption, resulting in only a small fraction of the CEC getting occupied by the ions. Although an increase in CEC due to alkali treatment increased the adsorption of ions, H+ ion saturated zeolites adsorbed higher amount of ions than the zeolites saturated with other cations. The cation-loaded zeolite was regenerated for ion adsorption by leaching with 0.5 M HCl, and even after 12 regeneration cycles the amount of ion adsorption remained unaffected, indicating the potential for recycling zeolite for removing ions from the waste stream.