| From the view of waste resource recycle, For solving the fluorine pollution problems during purifying uranium, two adsorbents, Zirconium(IV)-impregnated Hydrolyzed Granular Leather Waste (ZHGLW), Zirconium(IV)-impregnated Carboxylated Granular Leather Waste(ZCGLW), were prepared in this work. The sorptive properities for fluorine onto ZHGLW and ZCGLW from wastewater systematically through batch experiments as a function of solution pH, adsorbent dosage, temperature, contact time and initial fluoride ion concentration in the same time. The fluorion adsorption behavior on ZHGLW and ZCGLW was investigated by method of Scan electron microscope (SEM), Energy dispersive analysis of X-ray (EDX), X-ray photoelectron spectroscope (XPS), Fourier transform infrared spectroscopy, et al. And the fixed-bed column adsorption characteristic of fluoride was investigated by ZCGLW in detail. Besides, The regeneration properities for ZCGLW was also studied. The results were shown as follows.1. The optimal mass ratio of hydrolyzed granular leather waste(GLW) and Zr(NO3)4·5H2O was 1:3. The ZHGLW sorbent present a great adsorption capacity on removing of fluorion when pH was 3. And there was a high adsorption capacity at low temperature. The adsorption isotherm of fluorion was in conformity with the Langmuir equation, maximum adsorption capacity of the sorbent could reach 30.56 mg·g-1. The datum of adsorption rate could be well described by the pseudo-second-order model. The optimal mass ratio of GLW/Zr(IV) was 1:2. The optimal pH of adsorption was 3. The adsorption capacity could reach 49.72 mg·g-1 when the pH of 4. The adsorption isotherm of fluorion was in conformity with the Langmuir equation, maximum adsorption capacity of the sorbent could reach 33.99 mg·g-1. The adsorption kinetic data were fitted well with pseudo-second-order model.2. In the prepared process of ZHGLW, the-CO-NH2 in GLW was hydrolysed under the effect of NaOH, then the -OH replaced -NH2 to form-COOH, so appeared more carboxyl. In the prepared process of ZCGLW, the -CO-NH2 in GLW react with-CHO in glyoxalic acid to remove water to form-COOH, bringing in more carboxyl. The more carboxyl, there were more Zr(IV) to be loaded, then the excellent fluoride adsorbent would be prepared. In the process of adsorption, Zr(IV) the main activity sites, F- replaced-OH to combine with Zr(IV) to remove F-3. Fluoride sorption performance of the packed column was assessed under variable operating conditions, such as, initial influent ions concentration, bed depths and flow rate. It was found that the breakthrough time and depletion time were significantly shortened with an increase in flow rate and influent concentration, but obviously extended with an increase in bed heights. The adsorption belt length and velocity satisfied with the linear equation,?=1.275v+4.467. The experimental data of different bed depths was fitted well to the Bohrat-Adams model, the adsorption capacity for fluorine on ZCGLW, No reached 2.49×104 mg·L-1, the adsorption belt length, Ho was 3.44 cm.4. Experiments indicated that NaOH and NaHC03 were the best desorbent for F-. ZCGLW adsorbent regenerated in 0.01 mol-L-1 of NaOH solution, the flouride removal rate reached 86.29%, while reduced to 58.12% after 5 cycles in batch mode. The pH had a great influence in flouride removal rate, there was little desorption under acid condition, while in alkaline condition, the desorption rate increased significantly. After the pH reached 12, the desorption rate increase slowly.Based on all the experimental data and analyses, we can draw a conclusion that the modified granular leather waste adsorbents,as a wide source and low cost material, exhibited good sorption ability and adsorption selectivity. It could be a potential candidate in the field of fluorine wastewater treatment... |
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