State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu 210023, PR China.
Environ Sci Technol. 2014 May 6;48(9):5101-7. doi: 10.1021/es5004044. Epub 2014 Apr 23.
Hydrous manganese oxide (HMO) is generally negatively charged at circumneutral pH and cannot effectively remove anionic pollutants such as phosphate. Here we proposed a new strategy to enhance HMO-mediated phosphate removal by immobilizing nano-HMO within a polystyrene anion exchanger (NS). The resultant nanocomposite HMO@NS exhibited substantially enhanced phosphate removal in the presence of sulfate, chloride, and nitrate at greater levels. This is mainly attributed to the pHpzc shift from 6.2 for the bulky HMO to 10.5 for the capsulated HMO nanoparticles, where HMO nanoparticles are positively charged at neutral pH. The ammonium groups of NS also favor phosphate adsorption through the Donnan effect. Cyclic column adsorption experiment indicated that the fresh HMO@NS could treat 460 bed volumes (BV) of a synthetic influent (from the initial concentration of 2 mg P[PO4(3-)]/L to 0.5 mg P[PO4(3-)]/L), while only 80 BV for NS. After the first time of regeneration by NaOH-NaCl solution, the capacity of HMO@NS was lowered to ∼ 300 BV and then kept constant for the subsequent 5 runs, implying the presence of both the reversible and irreversible adsorption sites of nano-HMO. Additional column adsorption feeding with a real bioeffluent further validated great potential of HMO@NS in advanced wastewater treatment. This study may provide an alternative approach to expand the usability of other metal oxides in water treatment.
水合氧化锰（HMO）通常在近中性 pH 值下带负电荷，因此无法有效去除磷酸盐等阴离子污染物。在这里，我们提出了一种新的策略，通过将纳米 HMO 固定在聚苯乙烯阴离子交换剂（NS）内来增强 HMO 介导的磷酸盐去除。所得的纳米复合材料 HMO@NS 在存在硫酸盐、氯化物和硝酸盐的情况下，在更高的水平下表现出显著增强的磷酸盐去除能力。这主要归因于 HMO 从大块 HMO 的 pHpzc 从 6.2 转移到包裹的 HMO 纳米颗粒的 10.5，在中性 pH 下，HMO 纳米颗粒带正电荷。NS 的铵基也通过 Donnan 效应有利于磷酸盐的吸附。循环柱吸附实验表明，新鲜的 HMO@NS 可以处理 460 床体积（BV）的合成进水（从初始浓度 2mg P[PO4(3-)]/L 降至 0.5mg P[PO4(3-)]/L），而 NS 仅 80BV。用 NaOH-NaCl 溶液进行第一次再生后，HMO@NS 的容量降低到约 300BV，随后 5 次运行保持不变，这表明纳米 HMO 存在可逆和不可逆吸附位点。用实际的生物废水进行额外的柱吸附进料进一步验证了 HMO@NS 在深度废水处理中的巨大潜力。这项研究可能为在水处理中扩展其他金属氧化物的可用性提供了一种替代方法。
