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Al3+-bentonite clay (Alum-bent) was prepared by ion exchange of base cations on the matrices of bentonite clay. Intercalation of bentonite clay with Al3+ was performed in batch experiments. Parameters optimized include time, dosage, and Al3+ concentration. Physicochemical characterization of raw and modified bentonite clay was done by X-ray fluorescence, X-ray diffraction, energy dispersive X-ray spectrometry attached to scanning electron microscopy, Brunauer–Emmett–Teller analysis, cation exchange capacity (CEC) by ammonium acetate method, and pHpzc by solid addition method. Chemical constituents of water were determined by atomic absorption spectrometry (AAS), ion selective electrode (Crison 6955 Fluoride selective electrode) and a Crison multimeter probe. For fluoride removal, the effect of contact time, adsorbent dosage, adsorbate concentration, and pH were evaluated in batch procedures. The adsorption capacity of fluoride by modified bentonite clay was observed to be 5.7 mg g?1 at (26 ± 2) °C room temperature. Maximum adsorption of fluoride was optimum at 30 min, 1 g of dosage, 60 mg L?1 of adsorbate concentration, pH 2–12, and 1:100 solid/liquid (S/L) ratios. Kinetic studies revealed that fluoride adsorption fitted well to pseudo-second-order model than pseudo first order. Adsorption data fitted well to both the Langmuir and Freundlich adsorption isotherms, hence, confirming monolayer and multilayer adsorption. Alum-bent showed good stability in removing fluoride from ground water to below the prescribed limit as stipulated by World Health Organization. As such, it can be concluded that Alum-bent is a potential defluoridation adsorbent which can be applied in fabrication of point of use devices for defluoridation of fluoride-rich water in rural areas of South Africa and other developing countries. Based on that, this comparative study proves that Alum-bent is a promising adsorbent with a high adsorption capacity for fluoride and can be a substitute for conventional defluoridation methods. 相似文献
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共存氯离子对饮用水纳滤除氟的影响研究 总被引:3,自引:0,他引:3
采用深井地下水配水试验研究了高氟饮用水纳滤除氟的可行性、膜污染及共存氯离子浓度对纳滤除氟的影响.结果表明,纳滤对原水中的所有共存阴离子均有截留效果,原水F-浓度低于6 mg/L,纳滤出水的F-浓度低于1.2 mg/L,能满足农村地区的生活饮用水标准.随着F-浓度的增加,其截留率下降;进水共存Cl-浓度的增加,F-的截留率呈下降的趋势,F-的截留率降低的百分数在Cl-每增加1个mol数和氟离子增加0.1个mol数时相当,当Cl-浓度>220 mg/L时,F-的截留率有所上升,但变化没有达到显著水平.环境扫描电子显微镜、能谱分析和X-射线衍射(XRD)对膜污染成分分析表明,膜污染主要是晶体颗粒形状规则的无机碳酸钙,柠檬酸+氨水清洗可有效清除污染成分,恢复膜通量. 相似文献
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通过不同钙/磷物质的量比条件下合成羟基磷灰石(HAP),选用除氟容量最高的产物成球,并用FTIR、XRD、SEM对产物的结构进行表征.结果表明,成球以后羟基磷灰石的结构性质并没有发生改变.吸附试验表明,球状滤料的吸附过程受到吸附时间、温度、pH的影响;温度升高有利于吸附过程的进行,80 min内吸附基本达到平衡,吸附过程的最佳pH值在3左右.吸附过程接近单层吸附,吸附过程的△Hθ>0,△Gθ<0,说明吸附过程是自发吸热的过程.吸附过程中的ASθ为0.0292 kJ·mol-1·K-1. 相似文献
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采用吸附-超滤工艺进行饮用水除氟的试验研究,试验在恒流条件下进行,重点考察吸附剂粒径、膜区曝气量和回流量对除氟效果和膜污染的影响. 结果表明,粉末状的活性氧化铝较颗粒状吸附容量有了很大的提高. 在膜通量为150 mL/min,反冲周期为6 h,反冲时间为2 min,反冲流量为150 mL/min,原水ρ(氟)为2 mg/L,活性氧化铝投加量为0.1 g/L的条件下,选取活性氧化铝粒径为0.050~0.074 mm,膜区不曝气,沉淀区与反应区间的回流比为0.5(对应的回流量为4.5 L/h),可获得较好的除氟效果,并能有效地控制膜污染,使该系统在一定时间内稳定运行. 相似文献
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