Department of Chemical & Materials Engineering, University of Auckland, Auckland, 1010, New Zealand.
Water Research Centre, Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, PR China.
J Environ Manage. 2023 Jan 1;325(Pt B):116570. doi: 10.1016/j.jenvman.2022.116570. Epub 2022 Oct 26.
Struvite is a value-added by-product recovered from phosphorus-rich wastewater treatment by adding magnesium. Struvite is mainly used as slow-release fertilisers containing phosphate that can form insoluble salts with certain heavy metals. Hence, struvite may have potential application as a phosphate remediation agent for the immobilisation of heavy metals in contaminated soil, while the related study is limited. Similarly, an analogue compound of struvite, K-struvite, may also have this value but has not been reported elsewhere. This study investigated the effect of struvite and K-struvite on the remediation of Cr-spiked and Pb-spiked soil. To evaluate the feasibility, the agent dosage and two quality parameters (particle size and purity) of struvite and K-struvite were considered for the experimental design and statically analysed by principal component analysis (PCA) and partial least squares (PLS). The results show that the dosage significantly impacts the immobilisation process, while the effect of particle size and purity are negligible. Struvite and K-struvite have similar performance on heavy metals immobilisation, and both are significant in Pb immobilisation (up to 96% of F5, stable fraction) and are beneficial for reducing the most mobilised fractions (F1 and F2) of Cr to lesser than 3%. Struvite and K-struvite share similar performance due to their similar atomic radius, and the different performance between Cr and Pb immobilisation can be explained by the strong hydrolysis trend of chromium ion, which may inhibit the binding of the phosphate and chromium. The kinetic study finds that all three variables positively impact the free chromium ion, and the immobilisation process is fast so unlikely to be kinetically limited. These findings of this project will provide insight into how the immobilisation process changes in response to the dosage and quality of struvite compounds.
鸟粪石是一种从富含磷的废水处理中通过添加镁而回收的增值副产品。鸟粪石主要用作含有磷酸盐的缓释肥料，可与某些重金属形成不溶性盐。因此，鸟粪石可能具有作为固定污染土壤中重金属的磷修复剂的潜力，而相关研究有限。同样，鸟粪石的类似化合物 K-鸟粪石也可能具有这种价值，但尚未在其他地方报道。本研究调查了鸟粪石和 K-鸟粪石对铬和铅污染土壤修复的影响。为了评估可行性，考虑了鸟粪石和 K-鸟粪石的药剂用量和两个质量参数（粒径和纯度），并通过主成分分析（PCA）和偏最小二乘（PLS）进行了静态分析。结果表明，剂量对固定化过程有显著影响，而粒径和纯度的影响可以忽略不计。鸟粪石和 K-鸟粪石对重金属固定化的性能相似，对铅的固定化都很有效（高达 F5 的 96%，稳定分数），有利于降低最易移动的铬分数（F1 和 F2）至小于 3%。鸟粪石和 K-鸟粪石的性能相似，因为它们的原子半径相似，而铬和铅固定化之间的不同性能可以用铬离子的强烈水解趋势来解释，这可能抑制了磷酸盐和铬的结合。动力学研究发现，所有三个变量都对游离铬离子有积极影响，固定化过程很快，不太可能受到动力学限制。本项目的研究结果将深入了解固定化过程如何根据鸟粪石化合物的剂量和质量发生变化。
