Chemical sludge massively generated from chloride removal of saline wastewater by the Friedel’s salt precipitation method is difficult to handle and dispose. In this study, a novel process was proposed to recover dechlorination precipitate from saline wastewater as poly aluminum chloride (PAC). After Friedel’s salt precipitation, 55.7% of Cl^– could be removed with residual Al³⁺ of 1.86 mmol/L, yielding precipitate (14.3 g DS/g Cl^– removed) with Al₂O₃ content of 22.6% utilized for PAC preparation. The results of leaching experiments showed that 97.2% of Al³⁺ in precipitate could be extracted at fixed HCl concentration of 210 g/L, temperature of 353.15 K and leaching time of 180 min. The atomic force microscope images and Fourier transform infrared spectroscopy spectra confirmed that high basicity of PAC could be achieved with addition of CaO, which was favorable for reducing residual Al³⁺ in treated water. The dechlorination precipitate is more suitable than other solid wastes as raw material for PAC preparation owing to its Ca-based frameworks. PAC recovery could efficiently compensate chemical cost for Cl^– removal by 63.9% – 68.4%, which was economically beneficial and inspirable for utilization of Friedel’s salt in other domains.

用弗里德尔盐析法去除含盐废水的氯化物产生的大量化学污泥难以处理和处置。在这项研究中，提出了一种从含盐废水中以聚合氯化铝 (PAC) 形式回收脱氯沉淀物的新工艺。在 Friedel 盐沉淀后，55.7% 的 Cl ^–可以被去除，残留的 Al ³⁺为 1.86 mmol/L，产生沉淀物（14.3 g DS/g Cl ^–去除），Al ₂ O ₃含量为 22.6%，用于制备 PAC。浸出实验结果表明，97.2%的Al ³⁺在 210 g/L 的固定 HCl 浓度、353.15 K 的温度和 180 分钟的浸出时间下，可以提取沉淀中的 原子力显微镜图像和傅里叶变换红外光谱证实，加入CaO可以实现PAC的高碱度，有利于减少处理水中残留的Al ³⁺。由于其钙基骨架，脱氯沉淀物比其他固体废物更适合作为制备PAC的原料。PAC 回收率可以有效地补偿化学成本，去除Cl ^- 63.9% - 68.4%，这在经济上是有益的，并且对弗里德尔盐在其他领域的利用具有启发意义。