Study On Hydrotalcite-Like Compounds By IGC And Its Adsorption Property On Dye Wastewater

Magnesium-aluminum hydrotalcite-like compounds(Mg/Al-HTlc) was synthesized by coprecipitation.The calcined hydrotalcite-like compounds(C-HT) was obtained by calcination under 500℃and then the CoHT was modified with dodecylbenzene sulfonic acid sodium salt (SDBS) and Sodium dodecyl sulfate to yield the modification product (M-HT).The superficial properties of such materials have been characterized by inverse gas chromatography(IGC).The effect of surface modification on the properties of hydrotalcite-like compounds was also investigated.In addition,the adsorption mechanism of probes was further discussed.Furthermore,C-HT has been used to treat the NGB wastewater.The adsorption capacity of C-HT,MgO,Al₂O₃,mixture of MgO and Al₂O₃, the activated charcoal as well as the SiO₂ to NGB have been compared. The effects of various parameters on the removal of NGB such as dosage of adsorbent,pH of solution,temperature and competitive anions on adsorption were studied in detail.In addition,the regeneration of C-HT and the adsorption mechanism have also been investigated.The results show that:1.TheΔG⁰ andγs^d of the three materials have the following order:C-HT＞Mg/Al-HTIc＞M-HT.The values ofγs^d decrease with increasing measuring temperature for the C-HT and M-HT,while the values ofγs^d between non-polar probes and Mg/Al-HTlc are not affected by measuring temperature.In addition,the value ofΔG⁰ between the polar probes and the stationary phase includes the dispersive component and the specific component,and the modification lowers theΔG^sp of Mg/Al-HTlc.2.The C-HT was modified with different numbers(0-8%) of sodium dodecyl sulfate,the effect of dosage of sodium dodecyl sulfate on superficial properties has been studied,the results showed that:-ΔG⁰ andγs^d decrease with increasing the degree of modification of the C-HT surface.While,the value of-ΔH⁰ reach to the maximum when the dosage is 2%,and then decrease with increasing the degree of modification.By using non-alkane probes to estimateγs^sp,it showed that:the interaction between chloralkane and the surface of the material decreased with increasing the degree of modification.However,for the probe of acetone, the result was just opposite.3.The adsorption efficiency of NGB by different adsorbents has investigated in batch mode,it indicated that the C-HT has the best adsorption efficiency.The adsorption of NGB by C-HT has been studied particularly,the results indicate that:the maximum capacity of NGB adsorption at equilibrium is 193.4mg and the percentage of absorption is 96.7%,with an adsorbent dose of 1.0g·L^-1 under the following conditions: 200mg·L^-1 NGB concentration,temperature 298K,pH 10.0 and an equilibrium time of 50min.Langmuir and Freundlich adsorption models were used for fitting the isotherms,and the thermodynamic parameters have been calculated,it showed the adsorption process was spontaneous and exothermic in nature.In the light of so called "memory effect",C-HT was found to recover their original layered structure after adsorption,and part of NGB ions intercalated into the interlayer of HTlc which had been supported by XRD and FTIR.In addition,the competitive anions on adsorption and the regeneration of C-HT have also been investigated.