Photocatalytic reduction of nitrate using titanium dioxide for regeneration of ion exchange brine.
Photocatalytic reduction of nitrate using titanium dioxide for regeneration of ion exchange brine.
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DOI：
10.1016/j.watres.2012.11.047
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发表时间：
2013-03-01
期刊：
影响因子：
12.8
通讯作者：
Westerhoff P
中科院分区：
文献类型：
--
作者：
Yang T;Doudrick K;Westerhoff P
硝酸盐通常在用作饮用水之前通过离子交换（IX）从地下水中去除。硝酸盐在IX盐水中的积累降低了IX再生的效率和再生盐水的使用寿命。对于第一次，我们提出了一种策略，以光催化减少硝酸盐在IX盐水，从而扩大使用的盐水。当甲酸（FA）用作空穴清除剂时，用作光催化剂的二氧化钛（Evonik P90）在合成盐水和去除硫酸盐的IX盐水中有效地减少硝酸盐（即，电子供体），并且初始FA与硝酸盐的摩尔比（IFNR）为5.6。增加合成盐水中的NaCl水平减缓了硝酸盐还原速率，而不影响铵和气态N物质的副产物选择性（例如，N2、N2O）。在未改性的IX盐水中，由于硫酸盐的存在，硝酸盐的去除被极大地抑制，硫酸盐与硝酸盐竞争P90上的活性表面位点并诱导P90纳米颗粒的聚集。通过硫酸钡沉淀去除硫酸盐后，硝酸盐被有效地还原;大约需要3.6 × 1024光子将每摩尔硝酸盐还原到83%的N气体和17%的N气体。为了使FA的最佳利用和控制处理盐水中的残余FA水平，改变IFNR。高IFNR（例如，4，5.6）被发现是更有效的硝酸盐还原，但留下较高的残留FA在盐水中。进行IX柱测试以研究残留FA对盐水重复使用的影响。盐水中的残留FA没有显着影响IX树脂的硝酸盐去除能力，和甲酸盐污染的处理后的水可以通过用一个床体积的新鲜盐水冲洗消除。
Nitrate is often removed from groundwater by ion exchange (IX) before its use as drinking water. Accumulation of nitrate in IX brine reduces the efficiency of IX regeneration and the useful life of the regeneration brine. For the first time, we present a strategy to photocatalytically reduce nitrate in IX brine, thereby extending the use of the brine. Titanium dioxide (Evonik P90), acting as photocatalyst, reduced nitrate effectively in both synthetic brines and sulfate-removed IX brine when formic acid (FA) was used as the hole scavenger (i.e., electron donor) and the initial FA to nitrate molar ratio (IFNR) was 5.6. Increasing the NaCl level in the synthetic brine slowed the nitrate reduction rate without affecting byproduct selectivity of ammonium and gaseous N species (e.g., N2, N2O). In a non-modified IX brine, nitrate removal was greatly inhibited owing to the presence of sulfate, which competed with nitrate for active surface sites on P90 and induced aggregation of P90 nanoparticles. After removing sulfate through barium sulfate precipitation, nitrate was effectively reduced; approximately 3.6 × 1024 photons were required to reduce each mole of nitrate to 83% N Gases and 17% . To make optimum use of FA and control the residual FA level in treated brine, the IFNR was varied. High IFNRs (e.g., 4, 5.6) were found to be more efficient for nitrate reduction but left higher residual FA in brine. IX column tests were performed to investigate the impact of residual FA for brine reuse. The residual FA in the brine did not significantly affect the nitrate removal capacity of IX resins, and formate contamination of treated water could be eliminated by rinsing with one bed volume of fresh brine.