Preparation Of Zn/Al Hydrotalcite-like Compound And The Research On Capability Of Adsorption Reoval Of Anionic Surfactants From Aqueous Solution

A Zn/Al hydrotalcite-like compound was prepared by coprecipitation method, the hydrotalcite-like compound was calcined at 500℃, transformed into the Zn-Al-O mixed oxide type. Both LDH and LDO were characterized by TEM, SEM, XRD, TG-DTA-DSC, FTIR, BET surface area, and Zeta potential measurement. The removal of anionic surfactants from aqueous solution by the Zn/Al hydrotalcite-like compound and the Zn-Al-O mixed oxide was investigated respectively. The condition of the experiment and the effect factors were studied and the adsorption mechanism was discussed. The sorbent was regenerated when calcined at 500℃,and the capability of regeneration was studied. The experimental results showed that:(1)A mature Zn/Al hydrotalcite-like compound was prepared by controlling the condition of synthesizing experiment. The mature granule of sample is hexagonal multilayer in structure, and the degree of crystal is high, the shape is inerratic, the diameter of particles is symmetrical. The surface of particles is rough and has many holes, and this is advantageous for adsorption.(2)In different Zn/Al hydrotalcite-like compounds, the molar ratio of Zn/Al in mixed solution 2:1 (2Zn/Al-LDH) was the most effective at removing SDBS. The experimental data of SDBS removal by 2Zn/Al-LDH fits nicely with Langmuir isotherm, the saturated adsorption uptake can achieve 4869.5mg/g. So 2Zn/Al-LDH can be used for treating SDBS waste water of low concentration.(3)The calcined hydrotalcite was particularly effective at removing SDBS. The fine calcined temperature is 500℃. the optimum dose is 0.1g/L, the range of the optimum pH is 4～10, the optimum adsorption time is 30min. But the presence of additional anions, especially polyvalent anions, such as phosphate and sulfate, could affect the adsorption behavior of SDBS.(4)The experimental data of SDBS removal fits nicely with Langmuir isotherm. The saturated adsorption uptake of SDBS on 2Zn/Al-LDO at 10℃, 25℃, 40℃ decreased gradually. But it can achieve 4869.5mg/g at 40℃, so 2Zn/Al-LDO has extensive adjustability on temperature as an anion surfactant sorbent.(5)The sorbent was regenerated for many times when calcined at 500℃. The experimental data of SDBS adsorption on regenerated sorbent fits nicely with Langmuir isotherm. The saturated adsorption uptake of SDBS on 2Zn/Al-LDO, first regeneration sample, second regeneration sample decreased gradually. But the smallest can achieve 3511.5mg/g.(6)2Zn/Al-LDO was particularly effective at removing DBS, the optimal condition of experiment was obtained: the optimum dose is 0.2g/L, the optimum adsorption time is 30min, the range of the optimum pH is 4-10. The experimental data of DBS removal fits nicely with Langmuir isotherm, the saturated adsorption uptake can achieve 1819.3mg/g.(7)The adsorption of anion surfactant on Zn/Al hydrotalcite-like compound is a surface sorption process. But for the Zn-Al-O mixed oxide, it is a combination of surface adsorption and anion intercalation, and the surface adsorption is dominant. Compared with Zn/Al hydrotalcite-like compound, Zn-Al-O mixed oxide has the specialties as a sorbent: obvious removal of anion surfactant attained at low dose with high adsorption rate, high adsorption uptake, convenient and fast to regenerate. So Zn-Al-O mixed oxide is more adapt to be used as anion surfactant sorbent.