Wang Chun-Feng, Li Jian-Sheng, Wang Lian-Jun, Sun Xiu-Yun
School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, PR China.
J Hazard Mater. 2008 Jun 30;155(1-2):58-64. doi: 10.1016/j.jhazmat.2007.11.028. Epub 2007 Nov 17.
Synthesis of pure-form zeolite A were investigated using four concentrations of NaOH solution to dissolve Si source form fly ash, and with the addition of Al source, to prepare initial gel. Experimental results demonstrated, for two-stage method, that NaOH concentrations in initial gel played an important role in synthesis of pure-form zeolite A using fly ash as raw materials. Generally, pure-form zeolite A could be synthesized when following conditions were used: NaOH concentrations, 1.67, 5 and 6.67 M; the synthesis temperature, 100 degrees C; the corresponding crystallization time, 340, 250 and 190 min. However, a mixture phases of zeolites A and X were obtained at the condition of 3.33 M NaOH solution during various crystallization times. It was found that the higher NaOH concentration was used, the shorter crystallization time of zeolite A was required and the narrower particle size distribution of zeolite A was achieved. In addition, zeolite A submicron-crystals were first synthesized from fly ash using two-stage method in our study.
使用四种浓度的氢氧化钠溶液溶解粉煤灰中的硅源，并添加铝源来制备初始凝胶，对纯相A型沸石的合成进行了研究。实验结果表明，对于两步法，初始凝胶中的氢氧化钠浓度在以粉煤灰为原料合成纯相A型沸石的过程中起着重要作用。一般来说，当使用以下条件时可以合成纯相A型沸石：氢氧化钠浓度为1.67、5和6.67 M；合成温度为100℃；相应的结晶时间为340、250和190分钟。然而，在3.33 M氢氧化钠溶液的条件下，在不同的结晶时间内得到了A型和X型沸石的混合相。研究发现，氢氧化钠浓度越高，所需的A型沸石结晶时间越短，且A型沸石的粒径分布越窄。此外，在本研究中首次采用两步法从粉煤灰中合成了亚微米级的A型沸石晶体。
