Zekavat Soroosh Roshan, Raouf Fereshteh, Talesh Seyed Siamak Ashraf
Faculty of Engineering, Chemical Engineering at University of Guilan, P. O. Box 41635-3756, Rasht, Iran E-mail:
Water Sci Technol. 2020 Nov;82(9):1808-1824. doi: 10.2166/wst.2020.448.
Clinoptilolite modified by hexadecyltrimethylammonium bromide (HDTMA-Br) was used to simultaneously remove copper and hexavalent chromium from aqueous solutions. The surface properties of HDTMA-modified natural zeolite (HMNZ) were characterized using scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), zeta potential and Fourier transform infrared spectroscopy (FTIR) techniques. SEM images showed that surfactant is adsorbed on the surface of the zeolite, which is confirmed by the FTIR result. The results from BET demonstrated a reduction in the specific surface area and pore volume due to the presence of surfactant molecules on the external surface of zeolite. The effects of important parameters on adsorption efficiency of Cu and Cr (VI) were evaluated by Box-Behnken design. The Langmuir isotherm provided the best fit to the equilibrium data of Cu and Cr (VI), with the maximum adsorption capacity of 0.068 and 0.0093(mmolg), respectively. The film diffusion mechanism was found to control the mass transfer, and the adsorption reactions were computed as endothermic for Cu (ΔH = 17.58 kJmol) and exothermic for Cr (VI) (ΔH -26.18 kJmol). The results indicated that surfactant modification changes the surface charge of zeolite from negative to positive, which makes zeolites economic adsorbents with the possibility of simultaneous removal of cations and oxyanions. The results also showed that the removal efficiency of Cr (VI) increases in the presence of copper cations due to there being more positive sites on the adsorbent surface.
用十六烷基三甲基溴化铵（HDTMA-Br）改性的斜发沸石用于同时去除水溶液中的铜和六价铬。采用扫描电子显微镜（SEM）、布鲁诺尔-埃米特-泰勒（BET）、zeta电位和傅里叶变换红外光谱（FTIR）技术对HDTMA改性天然沸石（HMNZ）的表面性质进行了表征。SEM图像显示表面活性剂吸附在沸石表面，FTIR结果证实了这一点。BET结果表明，由于沸石外表面存在表面活性剂分子，比表面积和孔体积减小。采用Box-Behnken设计评估了重要参数对铜和六价铬吸附效率的影响。Langmuir等温线最适合铜和六价铬的平衡数据，最大吸附容量分别为0.068和0.0093（mmol/g）。发现膜扩散机制控制传质，计算得出铜的吸附反应为吸热反应（ΔH = 17.58 kJ/mol），六价铬的吸附反应为放热反应（ΔH = -26.18 kJ/mol）。结果表明，表面活性剂改性使沸石的表面电荷从负变为正，这使得沸石成为经济的吸附剂，有可能同时去除阳离子和阴离子。结果还表明，由于吸附剂表面有更多的正位点，在铜阳离子存在下六价铬的去除效率提高。
