弗氏盐法废水除氯产物资源化及二次利用进展

废水中高浓度氯离子不仅会腐蚀工业设备,还易污染水环境。目前,已报道了一系列去除废水中氯离子的技术,如膜分离或浓缩、蒸发结晶、化学沉淀、吸附、离子交换、电解、氧化和溶剂萃取等。化学沉淀法在设备投资和可操作性等方面具有较大的优势,其中,相对于基于银、铜或铋等除氯方法,弗氏盐沉淀除氯法因所用原料来源广、价格低而得到广泛研究。但弗氏盐沉淀除氯后会产生大量的化学污泥,这些污泥主要含有弗雷德盐(3CaO·Al_(2)O_(3)·CaCl_(2)·10H_(2)O)、加藤石[Ca_(3)Al_(2)(OH)_(12)]和氢氧化钙等,成分复杂,循环再生难。为使弗氏盐沉淀除氯法能够推广应用,对其除氯产物,特别是其中的弗雷德盐进行资源化再利用至关重要。本工作在介绍弗雷德盐成分结构特性的基础上,通过比较弗雷德盐不同制备方法,突出弗氏盐沉淀法(如超高石灰铝法和钙铝石法)既能去除氯离子又能得到弗雷德盐的优势。根据弗雷德盐含铝和钙成分和层状双金属氢氧化物结构特性,可进行有效的资源化利用,包括去除各类重金属阳离子(如Cu^(2+),Cd^(2+),Co^(2+),Zn^(2+),Pb^(2+))和含氧阴离子[如Sb(OH)_(6)^(-),AsO_(4)^(3-),SeO_(4)^(2-),CrO_(4)^(2-)],并制备聚合氯化铝混凝剂、作为污泥脱水调理剂等,这些用途都具有广阔的应用前景,为弗氏盐沉淀除氯法的进一步发展提供借鉴和探索方向。

Synthesis of novel magnetic sulfur-doped Fe_3O_4 nanoparticles for efficient removal of Pb(Ⅱ)

In this work, we report the synthesis of magnetic sulfur-doped Fe_3O_4 nanoparticles (Fe_3O_4:S NPs) with a novel simple strategy,which includes low temperature multicomponent mixing and high temperature sintering. The prepared Fe_3O_4:S NPs exhibit a much better adsorption performance towards Pb(Ⅱ) than bare Fe_3O_4 nanoparticles. FTIR, XPS, and XRD analyses suggested that the removal mechanisms of Pb(Ⅱ) by Fe_3O_4:S NPs were associated with the process of precipitation (formation of PbS), hydrolysis,and surface adsorption. The kinetic studies showed that the adsorption data were described well by a pseudo second-order kinetic model, and the adsorption isotherms could be presented by Freundlich isotherm model. Moreover, the adsorption was not significantly affected by the coexisting ions, and the adsorbent could be easily separated from water by an external magnetic field after Pb(Ⅱ) adsorption. Thus, Fe_3O_4:S NPs are supposed to be a good adsorbents for Pb(Ⅱ) ions in environmental remediation.