废物水泥窑共处置产品中重金属释放pH静态试验研究

pH-dependence Test Study on the Release of Heavy Metals in Cement Product from Co-processing Waste in Cement Kiln

通过模拟煅烧试验制取水泥熟料,并制取混凝土样品,将样品破碎至粒径小于1mm.采用pH静态(pH-dependence)试验研究pH对破碎混凝土样品中重金属(Cr,Ni,As,Cd和Pb)浸出特性的影响以及混凝土样品的酸中和容量.结果表明,混凝土的酸中和能力较大,浸出液pH降至6.87,需加入2.5mol/kg的硝酸,而浸出液pH降至1.46的过程中,需要消耗15mol/kg的硝酸,因此在一般的混凝土使用过程中,混凝土孔隙水的pH能在较长段时间内保持中性或弱碱性;浸提剂的酸碱性是影响混凝土中重金属浸出的重要参数,在试验研究的pH范围内,不同重金属的浸出规律不同;混凝土中重金属的浸出与其在混凝土中的存在形态及混凝土矿物对重金属的作用相关.

Clinker was prepared by simulating cement calcination, which was used to produce concrete samples and crushed into particles with diameter 〈 1 mm. The impacts of pH on the leaching behavior of heavy metals （Cr, Ni, As, Cd and Pb） and the ANC （acid neutralizing capacity） in crushed concrete samples were studied using the pH-dependence test. The results showed that the ANC of the concrete was large enough that it needed an addition of 2.5 mol/kg nitric acid to make the pH drop to 6.87 from lixiviating solution and 15 mol/kg nitric acid was needed to reduce the pH to 1.46. This was the reason that the pH of the pore water in the concrete was neutral or weakly acidic after a long time. The acidity and basieity of the leaching reagent were important factors impacting the leachability of heavy metals from concrete. In the investigated pH range, different heavy metals had different leaching characteristics. The leaching behavior of the heavy metals related to their forms in concrete and the adsorption of concrete minerals to heavy metals.