Advanced Treatment of Ammonium Removal from Coking Wastewater by Chemical Precipitation

摘要

NH4+-N removal by chemical precipitation is an efficient technology. In this paper, the removal of ammonium from coking wastewater was studied. The experiments were designed for the optimum pH, optimum molar ratio, and different kinds of chemicals combinations. And the kinetics of magnesium ammonium phosphate formation and X-ray diffraction analysis were discussed. The results indicated that NH4+-N contained in the coking wastewater could be removed most effective with the Mg2+: NH4+: PO43- mole ratio of 1.1:1:1 and the optimum pH of 10.5. High salinity formed in the experiments by using MgCl2·6H2O and Na2HPO4·12H2O. On the contrary, the two chemicals combinations of MgO plus 85% H3PO4 and Ca(H2PO4)2·H2O plus MgSO4·7H2O could significantly minimize the salt concentration after precipitation. In addition, the first order fitted to the MAP sedimentation. The X-ray diffraction analysis indicated that the sample was suit to the standards database and some formation of precipitates such as Mg2P2O7, (NH4)2H22P2O5 was possible in the sample systems.