钢渣吸附处理含铬废水的研究
钢渣吸附处理含铬废水的研究
摘 要
含铬废水来源于多种行业，其中Cr6＋能在环境和动植物体内蓄积，如过量摄入，会对人体健康产生不利影响。钢渣是炼钢过程排出的熔渣。钢渣疏松多孔，比表面积大，具有一定的吸附能力，而且钢渣的密度大，在水中的沉降速度快，易于固液分离。钢渣的碱性氧化物含量很高，因此溶于水时pH值较高。这样，对废水中的铬既具有化学沉淀作用，又具有吸附作用。既可提高废水处理的经济效益，又可以解决钢渣的处理处置问题。
本文以钢渣为吸附剂，处理实验室模拟含铬废水。实验结果表明钢渣对未经还原的Cr(VI)去除效率很低，最高去除率只有8.42%；经过高温处理和酸处理的钢渣并没有提高溶液中铬的去除率；经硫酸亚铁还原剂还原后，随着钢渣粒径的减小，铬的去除率明显增加，40～100目的钢渣中以100目钢渣去除率最好，在0.05g的投加量下50ml100mg/L含铬废水的去除率达到46.78%；钢渣投加量对铬去除率的影响不是很明显,对于50ml废水，0.10g的投加量下铬去除率为58.72%，0.25g的投加量下铬去除率为71.06%；随着振荡速度的增加，铬去除率增大，振荡速度为200r/min时达到峰值52.08%，此后再增加振荡速度去除率反而下降；25℃时，随着反应时间的增加，铬去除率开始快速增加，尔后缓慢增加，最后达到吸附平衡，可以认为35min便达到吸附平衡，此时去除率达到81.95%；反应温度对铬去除率影响较大，随着温度增加，去除率下降，25℃室温时去除率较佳；在酸性pH的条件下铬去除率较好，较佳溶液pH为2.85；在铬/钢渣质量比不变的条件下，铬浓度在500mg/L以内，其去除率随着浓度的增加而增大且均在81%以上；钢渣的吸附等温线相对符合BET和Frendlich型吸附等温线模式。
关键词：钢渣；含铬废水；吸附；硫酸亚铁；还原
Research on Treatment of Chromium-containing Wastewater by Adsorption of Steel Slag
Abstract
Chromium-containing wastewater is from a variety of industries, where the contained Cr6＋can be cumulated in environment and propagation, if taken excessively, it is harmful to mankind. Steel slag is the sprue discharged by steel-making process. It has definite sorption capacity because of being loose and porous, and holding large specific surface area, and due to great density it deposits rapidly and is easy to solid-liquid separation. The content of basic oxide of steel slag is quite high, therefore, when dissolved in water the pH is relatively high. Thus, there is chemical precipitation as well as adsorption to chromium in wastewater. Not only can it enhance economic benefit of effluent treatment, but also solve the problem of treatment and deposition of steel slag.
The simulation experiment on the treatment of chromium-containing wastewater by steel slag was conducted. The results showed that: the chromium removal rate of Cr(VI) by steel slag without reduction was low，and the highest one was just 8.42%; the steel slag treated both by high temperature and by acid did not increase the chromium removal rate in the solution; afer reduced by the reducer of ferrous sulphate, the chromium removal rate increased in evidence with particle size reducing, among 40～100 mesh, the 100 mesh of steel slag had the best chromium removal rate, when the content of steel slag was 0.05g, the removal rate of 50ml and 100mg/L chromium-containing wastewater reached 46.78%; the effect of content of steel slag on chromium removal rate was not evident, for 50ml wastewater, steel slag with 0.10g of content introduced 58.72% of chromium removal rate, while that with 0.25g of content introduced 71.06% of chromium removal rate; with the surge speed increasing, removal rate advanced, the surge speed with 200r/min made a peak value of 52.08%, then reincreace, on the contrary, removal rate descended; in the condition of 25℃, with the reaction time increasing, chromium removal rate began to increase rapidly, then increased slowly, finally reached adsorption equilibrium, we can consider that 35min attained adsorption equilibrium with a removal rate of 81.95%; reaction temperature had a relative influence on chromium removal rate which descended with temperature hoisting, when room-temperature 0f 25℃, the removal rate was relatively great; in the condition of acidic pH, chromium removal rate was comparatively good,the relatively great pH of solution was 2.85; with the mass ratio of Cr/steel invariable and within 500mg/L, the removal rate increased with concentration enhancing and all were above 81%; the adsorption isotherm of steel slag was according with the adsorption model of BET and Frendlich relatively.
Key words: steel slag; chromium-containing wastewater; adsorption; ferrous sulphate; reduction
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