灌浆工程中水泥水溶性铬（Ⅵ）对地下水的影响

水泥因其较好的综合性能而广泛应用于灌浆工程中,但多数水泥存在水溶性铬（Ⅵ）,可通过施工活动直接带入地表水及地下水中。本文分析了水泥中铬（Ⅵ）的现状,并以某大（2）型水库帷幕灌浆工程为对象,进行了地下水水质调查,结果表明：（1）采用水溶性铬（Ⅵ）含量为2.39 mg/kg的水泥产品进行灌浆,可引起周围地下水水质超标,超标持续时间随地下水更新速度变化,长可达2个月;（2）含铬（Ⅵ）水泥是一种灌浆过程中持续性、硬化后间断性的地下水铬（Ⅵ）污染源,以含铬（Ⅵ）水泥作为主要原材料进行大范围灌浆,存在对地下水造成污染的风险。     

硅酸钙粒径分析及吸附去除水中六价铬的研究

采用激光粒度分析仪对粉煤灰提取后的工业废物硅酸钙样品进行分析,结果表明硅酸钙样品的平均粒径在35.36 μm,分选性极好,样品频率曲线形态近似正态分布,峰态呈中等峰态.采用扫描电镜和X-射线能谱对硅酸钙样品表面进行分析,结果表明硅酸钙粒径大小不一、表面疏松多孔,由Ca、Si、O、C元素组成.设计正交实验研究了pH、反应温度、硅酸钙投加量以及六价铬溶液初始浓度对于反应去除率的影响,结果表明影响顺序为硅酸钙投加量＞溶液浓度＞反应温度＞ pH,反应在pH =6,反应温度30℃,硅酸钙投加量为30g/L,溶液浓度为1 mg/L的条件下取得最大去除率,六价铬去除率为16.51％.等温吸附实验结果表明Langmuir和Freundlich等温吸附模型均有较好模拟,硅酸钙对Cr6+的最大吸附容量为0.351 mg/g.     

压铸铝汽缸镀铬

阐述了压铸铝汽缸铬工艺及不合格支的无铬电退镀方法，并提供工艺配方 。     

含铬硫酸氢钠下脚料的处理及利用

本文主要研究将含铬的硫酸氢钠下脚料溶成溶液后，通过加入催化剂进行化学氧化法处理，使三价铬转化为六价铬，直接返回生产重铬酸钠的酸化工序，代替硫酸用于酸化铬酸钠。，这样既可利用硫酸氢钠中的酸性，节约硫酸，并加收六价铬，又解决了环境污染问题，有较好的环境效益及经济效益。     

Removal of hexavalent chromium by Kendu fruit gum dust

The ability of a low cost adsorbent material, Kendu fruit gum dust (KGD), for removal of hexavalent chromium, Cr(VI), from aqueous solutions of both a synthetic and industrial (effluent) sample is successfully investigated through batch type experiments. The effects of contact time, Cr(VI) concentration, pH, adsorbent amount, and temperature on the extent of Cr(VI) removal are reported. At a lower initial concentration of Cr(VI) and a lower solution pH, the percent removal is found to be increased. A removal efficiency of 100% has been achieved. In the presence of cyanide ion the adsorption efficiency of KGD decreases. Recycling studies suggest that even after the sixth cycle, only ∼ 20% loss of efficiency of KGD occurs. The adsorption process follows the Freundlich adsorption isotherm model. Another important feature of the investigation includes the studies on the characteristics and analysis of various constituents present in the newly developed absorbent material (KGD). From the thermogravimetric analysis curves of the original KGD and Cr(VI) absorbed KGD, it is observed that the thermal stability of KGD increases due to metal ion adsorption. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1485–1494, 1997     

混凝-吸附联合处理含铬废水的研究

采用新型混凝剂聚磷氯化铝铁(PPAFC)对含铬废水进行混凝处理;再采用铝化改性膨润土对含铬废水进行吸附处理。结果表明:在PPAFC 40mg/L,铝化改性膨润土2.0g/L,室温的条件下,总铬的去除率超过99.8%,出水中总铬的质量浓度达到《电镀污染物排放标准》(GB 21900-2008)要求。     

还原法处理含铬电镀废水的工艺研究

分别以亚硫酸氢钠、亚硫酸钠及焦亚硫酸钠为还原剂,在不同的条件下对电镀废水中Cr(Ⅵ)的还原效果进行了研究。考察了pH,还原剂、还原反应时间及工业成本对含铬废水处理的影响,最终确定了最佳反应条件。焦亚硫酸钠投加质量浓度为理论量的1.25倍,即1.418g/L,反应t为2 min,效果最好。为了不增加后续反应中产生的污泥量,选择以氢氧化钠作为沉淀反应的中和药剂,确定出中和沉淀反应t为30min。     

负载金属捕获剂改性PAC吸附低温水中低浓度Cr(Ⅵ)特性

针对低温微污染水中(275 K)低浓度Cr(Ⅵ)离子(0.500 mg·L^-1),制备基于表面负载食品级单宁酸为金属捕获剂的改性PAC(TA-PAC),以HNO₃、NaOH氧化改性PAC为对照,研究了TA-PAC的表面物理化学特性和吸附性能,并进行了pH影响和吸附等温线拟合研究。结果表明:TA-PAC的比表面积、总孔容积和表面极性大小最佳。TA-PAC对低温水中Cr(Ⅵ)及总铬的去除效果优于N-PAC和OH-PAC。酸性范围内(pH=3.0~6.0)TA-PAC对Cr(Ⅵ)及总铬的去除率均大于碱性范围(pH=7.0~10.0)。Freundlich 双参数吸附等温式对TA-HNC吸附水中低浓度总铬的吸附等温线拟合效果最好(R²=0.9941)。TA-PAC吸附低温水中低浓度Cr(Ⅵ)是一个极为复杂的过程,主要吸附机理可能包括表面还原作用、酯化/螯合作用和离子交换作用等。     

Optimal Synergistic Extraction of Cr(VI) from Aqueous Acidic Media Using Alamine 300/Aliquat 336 and Di-n-octyl Amine/Tributyl Phosphate Mixed Reagents

Data for the extraction of chromium(VI) from aqueous sulfate solutions by Alamine 300/Aliquat 336 and di–n–octyl amine/tributyl phosphate (DOA/TBP) have been subjected to formulation of an optimization structure for an effective Cr(VI) separation based on the derivative variation method. Both experimentally and analytically defined optimum Cr(VI) removal efficiencies are ranging about 83–99%, 71–93%, and 60–73% for Alamine 300/Aliquat 336, DOA/TBP, and DOA, respectively. Modeling efforts based on mass-action law methodology and non-homogeneous differential approach have shown considerable success yielding a 10% mean error, and satisfies established limiting behavior of the physical event.     

Hybrid Properties of Alginate‐PEI Adsorbent for Chromium (VI) Removal from Aqueous Solutions

Abstract

An adsorbent consisting of polyethyleneimine (PEI) immobilized in calcium alginate gel beads was synthesized and evaluated for Cr⁶⁺ removal. An evaluation of the synthesis process showed the importance of the PEI molecular weight on the immobilization efficiency. Polyethyleneimine of 70,000 Da molecular weight displayed the highest immobilization percentage at 52%. Batch kinetics and equilibrium tests showed that alginate‐PEI (APEI) resin displayed considerable affinity for negatively charged Cr⁶⁺ complexes at low pH conditions ranging from pH 1.5‐pH 3. The results also indicated the reduction of Cr⁶⁺ to less toxic Cr³⁺ species by the APEI adsorbent. The column adsorption experiments showed the ability of APEI resin to treat a 10 mg/L Cr⁶⁺ solution with pH influent adjustment from pH 1.5 to pH 3 to concentrations that satisfy effluent standards for Cr⁶⁺ (<0.1 mg/L) and total Cr (<0.5 mg/L). Finally, comparisons with a highly aminated commercial resin Chitopearl CS‐03 highlighted the unique ability of the hybrid APEI beads with its amine and carboxylic groups for the adsorption of Cr⁶⁺ as well as the retention of generated Cr³⁺ ions.