Ca/CTS/FA复合材料对酸性大红的吸附研究

Adsorption of acid scarlet 3R by Ca/CTS/ FA composite from aqueous solution

以粉煤灰(Fly ash,FA)为原料,通过负载壳聚糖和钙离子制备一种新型吸附剂(Ca/CTS/FA)用于酸性大红3R(Acid scarlet3R,AS 3R)染料的吸附去除,考察了最佳吸附条件和吸附性能,探讨了吸附动力学、吸附热力学及复合吸附剂的再生。结果表明:水体p H、吸附剂投加量、吸附时间和振荡频率均对吸附有影响。在不同温度下,Ca/CTS/FA对AS 3R的吸附动力学均能用准二级吸附速率方程精确描述(R^2=1.00)。不同温度下的等温吸附数据分别用Langmuir模型、Freundlich模型和Dubinin-Radushkevich(D-R)模型进行拟合,结果表明等温吸附行为更符合Langmuir模型,同时也较好地符合Freundlich模型和D-R模型;由D-R方程获得的平均吸附能、表观活化能及热力学研究均表明该吸附过程由化学吸附、物理吸附和氢键作用共同控制。热力学参数中吸附自由能变为负值、焓变为正值说明该吸附是吸热性质的自发过程。Ca/CTS/FA复合吸附剂能用0.01 mol·L-1Na OH溶液再生,至少可循环使用8次以上,再生率均在99%以上。

Dye-containing wastewater has caused severe water pollution. In this study, a new adsorbent, Ca/CTS/ FA composite prepared by loading chitosan and calcium ion onto fly ash was used to remove acid scarlet 3R（AS 3R）from aqueous solution. The optimum adsorption conditions and adsorption properties were investigated. Adsorption kinetics and thermodynamics and recycling of the composite adsorbent were discussed. Results showed that solution p H, adsorbent rate, contact time and oscillation frequency all affected AS 3R adsorption. The ad-sorption process could be well described by pseudo-second-order kinetic equation（R^2=1.00）. The isotherm data were fitted the Langmuir, Freundlich and D-R models, with Langmuir model being better than others. The average adsorption energy obtained by D-R model, the apparent activation energy and thermodynamic results showed that AS 3R was adsorbed through chemisorption, physical adsorption and hydrogen bonding. The negative values of adsorption Gibbs free energy changes（ΔG）and the positive values of adsorption enthalpy changes（ΔH）indicated that the adsorption process of AS 3R had spontaneous and endothermic nature. The FA/CTS/Ca material could be regenerated by 0.01mol·L^（-1） Na OH solution and reused at least 8 times for dye removal from aqueous solution. The regeneration rates were higher than 99%.