A simple and practical method for the synthesis of zeolite 4A from bauxite tailings is presented in this paper. Systematic investigations were carried out regarding the capacity of zeolite 4A to remove Cr(III) from ...A simple and practical method for the synthesis of zeolite 4A from bauxite tailings is presented in this paper. Systematic investigations were carried out regarding the capacity of zeolite 4A to remove Cr(III) from aqueous solutions with relatively low initial concentrations of Cr(III)(5–100 mg·L^(-1)). It is found that the new method is extremely cost-effective and can significantly contribute in decreasing environmental pollution caused by the dumping of bauxite tailings. The Cr(III) removal capacity highly depends on the initial p H value and concentration of Cr(III) in the solution. The maximum removal capacity of Cr(III) was evaluated to be 85.1 mg×g^(-1) for zeolite 4A, measured at an initial p H value of 4 and an initial Cr(III) concentration of 5 mg·L^(-1). This approach enables a higher removal capacity at lower concentrations of Cr(III), which is a clear advantage over the chemical precipitation method. The removal mechanism of Cr(III) by zeolite 4A was examined. The results suggest that both ion exchange and the surface adsorption-crystallization reaction are critical steps. These two steps collectively resulted in the high removal capacity of zeolite 4A to remove Cr(III).展开更多
为解决焦化废水尾水中有机物难降解问题,采用浸渍-煅烧法制备了负载活性金属氧化物的活性氧化铝型催化剂,通过臭氧催化氧化实验探索了载体和活性组分种类对COD去除率的影响,并对去除效率最高效的催化剂进行了表征分析。结果表明:BET分...为解决焦化废水尾水中有机物难降解问题,采用浸渍-煅烧法制备了负载活性金属氧化物的活性氧化铝型催化剂,通过臭氧催化氧化实验探索了载体和活性组分种类对COD去除率的影响,并对去除效率最高效的催化剂进行了表征分析。结果表明:BET分析发现Mn-Ni/γ-Al_(2)O_(3)(n_(Mn)∶n_(Ni)=2∶1)保留了γ-Al_(2)O_(3)的介孔结构,具有较大的表面积和孔体积,但负载后催化剂的比表面积和孔体积都有所降低,孔径变大;XPS和XRD分析发现锰主要以α-MnO_(2)形式存在,镍主要以复合价态存在,且二者存在强烈的相互作用;煅烧温度为450℃,煅烧时间为4 h,活性氧化铝载体催化活性最高;单组分催化剂相比于多组分催化剂,催化活性较低,其中Mn-Ni/γ-Al_(2)O_(3)的催化活性最好,60 min COD的去除率能达到43.26%,且重复使用6次后,COD的去除率仍达35.65%,催化活性仅降低17.60%,且Mn和Ni溶出量较低,表明催化剂具有良好的稳定性和重复使用性。展开更多
基金financially supported by the National High Technology Research and Development Program of China(No.2013AA032003)the National Natural Science Foundation of China(Nos.51372019,51272025,and 51072022)
文摘A simple and practical method for the synthesis of zeolite 4A from bauxite tailings is presented in this paper. Systematic investigations were carried out regarding the capacity of zeolite 4A to remove Cr(III) from aqueous solutions with relatively low initial concentrations of Cr(III)(5–100 mg·L^(-1)). It is found that the new method is extremely cost-effective and can significantly contribute in decreasing environmental pollution caused by the dumping of bauxite tailings. The Cr(III) removal capacity highly depends on the initial p H value and concentration of Cr(III) in the solution. The maximum removal capacity of Cr(III) was evaluated to be 85.1 mg×g^(-1) for zeolite 4A, measured at an initial p H value of 4 and an initial Cr(III) concentration of 5 mg·L^(-1). This approach enables a higher removal capacity at lower concentrations of Cr(III), which is a clear advantage over the chemical precipitation method. The removal mechanism of Cr(III) by zeolite 4A was examined. The results suggest that both ion exchange and the surface adsorption-crystallization reaction are critical steps. These two steps collectively resulted in the high removal capacity of zeolite 4A to remove Cr(III).
文摘为解决焦化废水尾水中有机物难降解问题,采用浸渍-煅烧法制备了负载活性金属氧化物的活性氧化铝型催化剂,通过臭氧催化氧化实验探索了载体和活性组分种类对COD去除率的影响,并对去除效率最高效的催化剂进行了表征分析。结果表明:BET分析发现Mn-Ni/γ-Al_(2)O_(3)(n_(Mn)∶n_(Ni)=2∶1)保留了γ-Al_(2)O_(3)的介孔结构,具有较大的表面积和孔体积,但负载后催化剂的比表面积和孔体积都有所降低,孔径变大;XPS和XRD分析发现锰主要以α-MnO_(2)形式存在,镍主要以复合价态存在,且二者存在强烈的相互作用;煅烧温度为450℃,煅烧时间为4 h,活性氧化铝载体催化活性最高;单组分催化剂相比于多组分催化剂,催化活性较低,其中Mn-Ni/γ-Al_(2)O_(3)的催化活性最好,60 min COD的去除率能达到43.26%,且重复使用6次后,COD的去除率仍达35.65%,催化活性仅降低17.60%,且Mn和Ni溶出量较低,表明催化剂具有良好的稳定性和重复使用性。