重金属制粉洗涤废水中氨氮资源回收工艺的研究

采用蒸发结晶与磷酸铵镁结晶沉淀法组合处理一种重金属深加工制粉工艺中产生的氨氮废水,探索了该废水处理的工艺路径与关键工艺参数。利用扫描电镜、红外光谱仪、激光粒度分布仪对产物进行了分析,考察了蒸发结晶法中蒸发温度、pH值、搅拌速度与磷酸铵镁结晶沉淀法中反应pH值、反应时间、药剂投加比对废水中氨氮的资源化回收的影响。结果表明,高浓度氨氮废水采用蒸发结晶法,通过硝酸调节pH值为5、温度为80℃、转速为300r/min时回收硝酸铵晶体为分析纯,粒度分布均匀,回收率达到97.04%;将高浓度氨氮废水蒸发结晶后产生的冷凝水与低浓度氨氮废水混合,采用磷酸铵镁结晶沉淀法资源化回收废水中的氨氮,当pH值为9、反应时间为120min、药剂投加比为wMg∶wN∶wP=1.2∶1∶1.2时,出水氨氮达到《污水综合排放标准》(GB8978-1996)一级排放标准15mg/L,磷酸铵镁的回收率达到94.53%。分析纯硝酸铵与磷酸铵镁外售后得到的经济效益抵消废水治理成本后还能产生一定的盈利。

Study on the Recovery Process of Ammonia and Nitrogen Resources from Heavy Metal Powder Washing Wastewater

The ammonia-nitrogen wastewater from a kind of heavy metal deep processing pulverization process was treated by evaporation crystallization and magnesium ammonium phosphate crystallization precipitation method. The effects of evaporation temperature,pH value,stirring speed,reaction pH value,reaction time and the ratio of chemical addition on the recovery of ammonia nitrogen in wastewater were investigated. Results show that high concentration of ammonia nitrogen wastewater by evaporation crystallization method,by nitric acid to adjust pH value of 5,the temperature is 80 ℃,the speed of 300 r/min recovery for the analysis of pure ammonium nitrate crystals,uniform particle size distribution,recovery rate of 97. 04%;To high concentration of ammonia nitrogen wastewater after evaporation crystallization of condensed water mixed with low concentration ammonia nitrogen wastewater,magnesium ammonium phosphate crystallization precipitation resource recovery of ammonia nitrogen in wastewater,when the pH value of 9,the reaction time of 120 min,drug dosing ratio of 1. 2∶ 1∶ 1. 2 for wMg ∶ wN∶ wP,the water ammonia nitrogen to achieve " integrated wastewater discharge standard"( GB8978-1996 ) level of emission standard of 15 Mg /L, magnesium ammonium phosphate recovery rate reached 94. 53%. The economic benefit of pure ammonium nitrate and magnesium ammonium phosphate after sale can offset the cost of wastewater treatment.