用电导超滤膜去除 As(III)。
Removal of As(III) by Electrically Conducting Ultrafiltration Membranes.
机构信息
Department of Civil and Environmental Engineering, University of California, Los Angeles, Los Angeles, CA, United States.
Department of Civil and Environmental Engineering, University of California, Los Angeles, Los Angeles, CA, United States; Laboratory for the Chemistry of Construction Materials (LC2), University of California, Los Angeles, CA, United States; Institute for Carbon Management (ICM), University of California, Los Angeles, CA, United States.
出版信息
Water Res. 2021 Oct 1;204:117592. doi: 10.1016/j.watres.2021.117592. Epub 2021 Aug 25.
As(III) species are the predominant form of arsenic found in groundwater. However, nanofiltration (NF) and reverse osmosis (RO) membranes are often unable to effectively reject As(III). In this study, we fabricate highly conducting ultrafiltration (UF) membranes for effective As(III) rejection. These membranes consist of a hydrophilic nickel-carbon nanotubes layer deposited on a UF support, and used as cathodes. Applying cathodic potentials significantly increased As(III) rejection in synthetic/real tap water, a result of locally elevated pH that is brought upon through water electrolysis at the membrane/water interface. The elevated pH conditions convert HASO to HAsO/HAsO that are rejected by the negatively charged membranes. In addition, it was found that Mg(OH) that precipitates on the membrane can further trap arsenic. Importantly, almost all As(III) passing through the membranes is oxidized to As(V) by hydrogen peroxide produced on the cathode, which significantly decreased its overall toxicity and mobility. Although the high pH along the membrane surface led to mineral scaling, this scale could be partially removed by backwashing the membrane. To the best of our knowledge, this is the first report of effective As(III) removal using low-pressure membranes, with As(III) rejection higher than that achieved by NF and RO, and high water permeance.
在地下水中，砷的主要存在形式为 As(III)。然而，纳滤（NF）和反渗透（RO）膜通常无法有效去除 As(III)。在本研究中，我们制备了高导电性超滤（UF）膜，以实现有效去除 As(III)。这些膜由沉积在 UF 支撑体上的亲水性镍-碳纳米管层组成，用作阴极。施加阴极电势可显著提高合成/实际自来水的 As(III)去除率，这是由于在膜/水界面处通过水的电解局部升高 pH 值所致。升高的 pH 值条件将 HASO 转化为 HAsO/HAsO，这些物质被带负电荷的膜排斥。此外，还发现沉淀在膜上的 Mg(OH) 可以进一步捕获砷。重要的是，几乎所有通过膜的 As(III)都被阴极上产生的过氧化氢氧化为 As(V)，这大大降低了其整体毒性和迁移性。尽管膜表面的高 pH 值导致矿物结垢，但通过对膜进行反冲洗可以部分去除这种结垢。据我们所知，这是首次使用低压膜有效去除 As(III)的报道，其 As(III)去除率高于 NF 和 RO，且水通量高。
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