酸碱预处理对鸟粪石结晶产物性质的影响

Effect of Acid and Alkaline Pretreatment on the Properties of Struvite Crystallization Recovered Products

为探求酸碱预处理剩余污泥对鸟粪石法结晶产物性质的影响,分别对酸、碱预处理剩余污泥后的溶出液进行鸟粪石结晶实验。结果表明,酸预处理后NH_3-N和PO_4^(3-)-P的溶出量均比碱预处理大,而碱溶出液产物中鸟粪石晶体纯度高、结晶度高和颗粒大。当溶出液n(Mg):n(N):n(P)为1:1:1时,继续加大NH_3-N和Mg^(2+)的投加量均有助于提高酸溶出液结晶产物中鸟粪石纯度和结晶度;但对碱溶出液结晶产物中鸟粪石的纯度和结晶度影响不大。场发射扫描电子显微镜形貌和能谱分析结果表明,酸溶出液结晶产物中鸟粪石表面被大量的无定形磷酸钙覆盖并掩蔽,阻碍其进一步生长,其颗粒小且纯度低;而碱溶出液结晶产物为柱状型的鸟粪石晶体,其颗粒大且纯度高。

In order to explore the effect of acid and alkaline pretreatment of wasted sludge on the properties of products recovered from struvite crystallization, the supernatant of acid or alkaline pretreated waste activated sludge was used to struvite crystallization. The results showed that dissolving-out amount of NH3-N and PO43--P from acid-pretreated sludge was more than that of alkaline-pretreated sludge. But alkaline-pretreated struvite crystal had high purity and crystallinity, and big particle. When n（Mg）：rt（N）：n（P） was 1：1：1, the excessive Mg and N dosage improved markedly the purity and crystallinity of struvite crystals recovered from acid-treated sludge, but had little effect on those from alkaline-treated sludge. The scanning electron microscopy and energy dispersive X-ray analysis indicated that the surface ofstruvite recovered from acid-treated sludge was not smooth and covered with the amount of amorphous calcium phosphate, which resulted in small particles with low purity. In contrast, struvite recovered from alkaline-treated sludge presents bigger particles with higher purity.