As(Ⅴ)-Fe(Ⅱ)体系常压臭葱石合成过程过饱和度对形貌和稳定性的影响

Effect of supersaturation on morphology and stability of atmospheric pressure scorodite under As(Ⅴ)-Fe(Ⅱ)system

针对低溶液过饱和度是常压臭葱石合成过程的关键要素这一问题,本文在As(Ⅴ)-Fe(Ⅱ)体系下,通过Fe2+缓慢氧化来控制溶液过饱和度,研究了pH对Fe2+氧化速率的影响、Fe2+氧化速率与过饱和度的关系和过饱和度对砷铁沉淀率、臭葱石组分含量、颗粒粒径、形貌及其稳定性的影响。结果表明,Fe2+的氧化速率随初始pH值的降低而降低,而溶液过饱和度随Fe2+氧化速率的降低而降低。较低的初始过饱和度不利于砷铁的沉淀,对渣中砷铁含量影响不显著,但对渣中硫含量影响较大。初始过饱和度从7.86升至78.86时,砷、铁沉淀率分别从77.05%、53.9%升至88.66%、61.79%,渣中砷、铁和硫含量分别为30.74%、24.14%和0.58%~0.17%。臭葱石颗粒粒径随初始过饱和度的增加而先增加后减小,初始过饱和度值为11.7时,颗粒尺寸达到最大87.5μm。初始过饱和度为7.86~24时,形成类球型臭葱石颗粒;初始过饱和度值为24~78.86时,形成无规则型臭葱石颗粒。通过控制初始过饱和度在7.86~78.86下,合成的臭葱石稳定性高,其浸出毒性均小于1 mg/L。

According to the problem that low solution supersaturation was the key factor in the process of scorodite synthesis under atmospheric pressure,the effect of pH on the oxidation rate of ferrous iron,the relationship between the oxidation rate of ferrous iron and supersaturation,and the effect of supersaturation on the precipitation percent of arsenic and iron,the content of scorodite components,particle size,morphology and stability were investigated in an As(Ⅴ)-Fe(Ⅱ)system by slow oxidation of ferrous ions.The results show that the oxidation rate of ferrous ions decreases with the decrease of initial pH value,while the supersaturation of solution decreases with the decrease of oxidation rate of ferrous ions.Lower initial supersaturation is not conducive to the precipitation of As and Fe,and has no significant influence on the content of arsenic and iron in the synthesized scorodite but has a greater impact on the sulfur content in synthesized scorodite.The initial supersaturation increases from 7.86 to 78.86,and the arsenic iron precipitation percent increases from 77.05%and 53.9%to 88.66%and 61.79%,respectively,and the contents of arsenic,iron and sulfur in the scorodite are 30.74%,24.14%and 0.58%?0.17%,respectively.The particle size of scorodite first increases and then decreases with an increase of initial supersaturation.When the initial supersaturation is 11.7,the particle size reaches a maximum of 87.5μm.The initial supersaturation is in the range from 7.86 to 24,the spheroidoid particles are synthesized.The initial supersaturation is in the range from 24 to 78.86,it is irregular scorodite particles.By controlling the initial supersaturation in the range of 7.86-78.86,the stability of the synthesized scorodite is high,and its leaching toxicity is less than 1 mg/L.