环境因素对水铁矿-砷共沉淀体系稳定性的影响

Effect of External Environmental Factors on the Stability of Ferrihydrite-Arsenic Coprecipitation System

铁(Fe)-砷(As)的共沉淀作用是处理工业含砷废水以及自然环境中铁氧化物控制砷的生物有效性重要途径,但在某些环境条件下其结构发生转化,潜在砷向环境中二次释放的风险。通过人工合成水铁矿-砷共沉淀物,探究不同pH值、温度及Fe(II)浓度对其影响。研究结果表明:不同的环境因素能够影响共沉淀体系的稳定性,导致砷向溶液中的释放。其稳定性在3种不同pH值条件下表现出明显差异(P<0.05)。在碱性条件(pH=10)下稳定最差,砷的释放量最大,其次为中性(pH=7)和酸性条件(pH=4)。其稳定性随温度变化也较为明显(P<0.05),在75℃水浴条件下其稳定性最弱,其次为40和25℃,其中在常温25℃条件下几乎没有砷向溶液中释放,共沉淀体系的稳定性较高。不同浓度的Fe(II)对共沉淀体系影响具有显著性差异(P<0.05),在50 mmol/L的Fe(II)溶液中水铁矿-砷共沉淀体系的稳定性明显弱于5 mmol/L的Fe(II),砷的释放量相对较高,但在未添加Fe(II)的处理中仅有少量的砷释放到溶液中。

Coprecipitation of iron(Fe)-arsenic(As)is an important way to treat industrial wastewater containing arsenic and to control arsenic bioavailability by iron oxides in natural environment.However,under certain environmental conditions,the structure of iron(Fe)-arsenic(As)is transformed and the potential risk of secondary release of arsenic into the environment occurs.The effects of different pH,temperature and Fe(II)concentration on the precipitates were investigated by synthesizing the coprecipitates of ferrihydrite and arsenic.The results showed that different environmental factors can affect the stability of the coprecipitation system and lead to the release of arsenic into the solution.Its stability showed significant difference under three different pH conditions(P<0.05).Under alkaline conditions(pH=10),the stability was the worst,and the release of arsenic was the largest,followed by neutral(pH=7)and acidic conditions(pH=4).The stability also changed with temperature(P<0.05);under the condition of water bath at 75℃,its stability was the weakest followed by 40℃and 25℃;almost no arsenic was released to the solution at 25℃,and the stability of the coprecipitation system was higher.The effects of different concentrations of Fe(II)on the coprecipitation system were significantly different(P<0.05).The stability of the ferrihydrite-arsenic coprecipitation system in 50 mmol/L Fe(II)solution was significantly weaker than that in 5 mmol/L Fe(II),the release of arsenic was relatively high,but only a small amount of arsenic was released into the solution without adding Fe(II).