| Advanced oxidation technologies have been widely used for their high oxidation ability and no secondary pollutions.Photoassisted Fenton process is one of the most commonly used methods,while the existing disadvantages of homogeneous photoassisted Fenton technology has prompt the study of supported catalyst.In this paper,bentonite was chosen as catalyst carrier because of its cheapness and abundant reserves.Bentonite was pillared by using its ability to exchange the interlayer ions with other cations.Bentonite was pillared by different ratio of Fe,Cr and Al to obtain Fe-Cr-Al pillared bentonite and it was fixed in the paper by wet-end additon to obtained catalytic paper.Its strength,catalytic activity and stability during the recycling process were studied.Firstly,the influence of slurry concentration,dosage of sodium agent,reaction temperature,reaction time was studied.Bentonite obtained its best character after the10%bentonite slurry was treated by 3%Na2CO3 at 60?for 1.5h.It could be seen that the swellvalue increased from 19.7 ml/g to 86.2 ml/g,the blue absorption power from33.6 g/100 g to 43.6 g/100 g,cationic exchange capacity from 0.384 mmol/g to 1.026mmol/g and silt content from 10.5%to 0.5%.The content of montmorillonite increased from 76.0%to 98.6%and high-purity bentonite was obtained.Secondly,Fe,Cr and Al were chosen as the pillared metals and the influence of their ratio on the interlayer spacing and on the catalytic activity was studied.If the metal concentration was fixed to 0.2 mol/L and the ratio of Fe-Al and Fe-Cr were 9:1and 3:7,respectively,the bimetal pillared bentonite obtained their best decolorization.Their interlayers increased to 1.7902 nm and 1.832 nm,respectively.If the ratio of the three metals was 2.1:4.9:3,the Fe-Cr-Al pillared bentonite obtained high decoloration of 96.3%and its interlayer spacing was 1.876 nm.Thirdly,single factor experiments were used to discuss the effect of pillaring agent preparation and pillaring porcess on catalytic activity.The optimized pillaring conditions were determined as follows:the total concentration three metal ions of0.3mol/L,the ratio of OH-to metal of 2.5,the pillaring agent aging time of 15 days,the the proportion metal to bentonite of 10 mmol/g,the slurry aging time of 7 days,the heat treatment temperature of 300?.Fourly,the Software Design-Expert.8.05b was used to determine the optimum condition.The total metal concentration was 0.28 mol/L,the ratio of OH-to metal was2.4 and the ratio of metals to bentonite was 13 mmol/g.Three parallel experiments were conducted to verify the optimum results.The average decolorization of Acid Orange II was 95.0%,and the relative error of predictive value was 0.63%.Under the optimum conditions,the interlayer spacing of the Fe-Cr-Al pillared bentonite increased from 1.229 nm to 1.978 nm and the specific surface area increased from 49.98 m2/g to214.78 m2/g.Its structure has been improved significantly.Lastly,the Fe-Cr-Al pillared bentonite was fixed in the paper by papermaking technique.When the additive amount of bentonite was 40 g/m2,the catalytic paper obtained its best performance.The decolorization rate of acid orange II for was up to73.2%for 3 hours,and the retention rate of bentonite was about 90.6%.Under the condition of low pH,the catalytic paper had a good catalytic activity.With the increase of pH,the catalytic activity decreased.Even if pH reached 11,the decolorization rate of 3 hours could still reach up to 56.7%.With the increase of the dosage of H2O2,the decolorization rate of Acid Orange II increased first and then kept a stable level.If the light irradiation of 254 nm wavelength was chosen,high decolorization rate could be obtained.The catalytic paper had a recycling ability.The decoloration rate could exceed 40%and keep stable during the first 4 cycles.If the catalytic paper was used for more than 5 cycles,its catalytic activity decreased significantly. |
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