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Ion-exchange (IX): Arsenic and chromium removal from brines and removal of inorganic contaminants by specialty resins.

机译：离子交换（IX）：从盐水中去除砷和铬，以及通过特种树脂去除无机污染物。

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摘要

Although ion exchange is highly efficient in removing inorganic contaminants, similar to other water treatment technologies, ion exchange has some drawbacks that need to be studied further. Three issues related to drawbacks of ion-exchange resins in water treatment were addressed in this research. The first issue was the influence of anionic inorganic co-contaminants including nitrate, Cr(VI), Se(VI), and As(V) on the performances of nitrate and perchlorate specialty (selective) resins in water treatment. It was found that nitrate can be removed from waters using perchlorate specialty resins, but the resin is poorly regenerated. Perchlorate was not easily removed from either nitrate or perchlorate specialty resins. The results showed that simultaneous removal of nitrate and Cr(VI) is optimal when using nitrate specialty resin. Perchlorate/nitrate specialty resins were inefficient in removing As(V), but could exchange Cr(VI) or Se(VI). A major issue realized from this research is the accumulation of co-contaminants in specialty resins and their release during resin regeneration. Such a release may deem waste regenerant brines hazardous, significantly affecting disposal costs. The presence of the co-contaminant ions affected the run length and the brine composition when perchlorate or nitrate specialty resins were used. Brine treatment is a serious challenge for IX water industry when removing arsenic (V) or chromium (VI) from drinking water.;Arsenic (V) removal from brines using ferric chloride was the second issue of this research. The optimum pH range for the process was found to be 4.5-6.5. Higher brine alkalinity affected coagulation because it commands larger amounts of acid to lower the pH to the desired level. Increasing ionic strength slightly enhanced the arsenic (V) removal efficiency. For arsenic (V) concentrations typical in ion exchange brines and to achieve a remaining As (V) concentration of 5 mg/L, Fe/As molar ratios varying from 1.3 to 1.7 are needed at operating pH values of 5.5 to 6.5. The Fe/As ratios needed to treat brines are significantly lower than those used to treat drinking waters. Solids concentration varying from 2 to 18 mg/L were found.;The third issue of this research was chromium removal from IX brines. Optimum pH range for the process was found to be 8-10.3. The chromium removal efficiency improved only slightly when the ionic strength increased from 0.1 M to 1.5 M. For chromium (VI) concentrations typically found in IX brines, a CaS5/Cr(VI) molar ratio varying from 0.6 to 1.4 was needed to obtain a final chromium concentration below 5 mg/L. The maximum total chromium removal efficiencies were obtained at reducing conditions when oxidation reduction potentials of the brines were between -0.1 to 0 V. Solids concentrations varying from 0.2 to 1.5 g/L were found. The results of this research have direct application to the treatment of residual wastes brines containing chromium.
机译：尽管离子交换在去除无机污染物方面非常高效，但与其他水处理技术类似，离子交换还有一些缺点需要进一步研究。这项研究解决了与离子交换树脂在水处理中的缺点有关的三个问题。第一个问题是阴离子无机共污染物包括硝酸盐，Cr（VI），Se（VI）和As（V）对水处理中硝酸盐和高氯酸盐特种（选择性）树脂性能的影响。发现可以使用高氯酸盐特种树脂从水中去除硝酸盐，但该树脂再生差。高氯酸盐很难从硝酸盐或高氯酸盐特种树脂中去除。结果表明，使用硝酸盐专用树脂时，同时去除硝酸盐和Cr（VI）的效果最佳。高氯酸盐/硝酸盐特种树脂不能有效去除As（V），但可以交换Cr（VI）或Se（VI）。这项研究认识到的一个主要问题是特种树脂中污染物的积累及其在树脂再生过程中的释放。这样的释放可能认为废再生盐水是有害的，从而极大地影响了处置成本。当使用高氯酸盐或硝酸盐特种树脂时，共污染物离子的存在会影响运行时间和盐水成分。当从饮用水中去除砷（V）或铬（VI）时，盐水处理对于IX水工业而言是一个严峻的挑战。使用氯化铁去除盐水中的砷（V）是本研究的第二个问题。发现该方法的最佳pH范围是4.5-6.5。较高的盐水碱度会影响凝结，因为它需要大量的酸以将pH降低至所需水平。离子强度的提高略微提高了砷（V）的去除效率。对于离子交换盐水中典型的砷（V）浓度，以及要使剩余的As（V）浓度达到5 mg / L，在5.5至6.5的工作pH值下，Fe / As摩尔比需要在1.3至1.7之间变化。处理盐水所需的铁/砷比明显低于处理饮用水所需的铁/砷比。发现固体浓度在2到18 mg / L之间。该研究的第三个问题是从IX盐水中去除铬。发现该方法的最佳pH范围是8-10.3。当离子强度从0.1 M增加到1.5 M时，铬去除效率仅略有提高。对于通常在IX盐水中发现的铬（VI）浓度，需要CaS5 / Cr（VI）摩尔比从0.6到1.4变化才能获得最终铬浓度低于5 mg / L。当盐水的氧化还原电位在-0.1至0 V之间时，在还原条件下可获得最大的总铬去除效​​率。发现固体浓度在0.2至1.5 g / L之间变化。这项研究的结果直接用于处理含铬的废渣盐水。

著录项

  • 作者

    Pakzadeh, Behrang.;

  • 作者单位

    University of Nevada, Las Vegas.;

  • 授予单位 University of Nevada, Las Vegas.;
  • 学科 Engineering Environmental.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 424 p.
  • 总页数 424
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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