| Heterogeneous Fenton oxidation process with high utilization of H2O2, a wide range ofpH and catalysts reuse, has become an important improvement and development direction ofFenton technical, and provides an effective way for papermaking wastewater treatment. Inthis paper, Fe/Mn/sepiolite heterogeneous catalyst was prepared based on activated sepioliteas the carrier. Heterogeneous photo-Fenton process using Fe/Mn/sepiolite as catalyst wasstudied to degrade pulping wastewater, and a coupled coagulation-heterogeneous Fenton pro-cess was applied for the treatment of papermaking-reconstituted tobacco slice wastewater.Natural sepiolite was activated by acid and thermal pre-treatment to improve its perfor-mance. The results indicated that specific surface area of sepiolite was markedly increased,the structure and distribution of pores were improved, and the adsorption capacity was en-hanced by nitric acid activation. It was found that during the acid treatment there was a strongcorrelation between magnesium removal and specific surface area of sepiolite, and magnesi-um removal could be as the basis to evaluate the effect of acid activation. When magnesiumremoval was about59%, the maximum of specific surface area and the maximum of adsorp-tion capacity were obtained. The performance of sepiolite was further improved by ther-mal activation after acid activation. The optimized conditions of sepiolite activation were ni-tric acid concentration2.0mol/L, acid activation temperature40℃, acid activation time120min, solid-liquid ratio of1:20, calcination temperature300℃, and calcination time3h. Thespecific surface area of activated sepiolite was3.4times of natural sepiolite, the adsorptioncapacity of activated sepiolite was2.66times of natural sepiolite.Fe/Mn/sepiolite heterogeneous catalyst was prepared by coprecipitation method. Severalmethods such as XRD, SEM, XRF and BET were applied to investigate the characteristics ofsepiolite. It was also observed that the contents of iron and manganese increased significantly,the crystallinity of sepiolite degree decreased, iron and manganese present in the surface andpore of sepiolite in the form of monodisperse, specific surface area and pore volume were stilllarge.The catalytic performances Fe/Mn/sepiolite catalyst were studied by p-chlorophenoldegration. The results showed that the catalytic activity of catalyst was very high in the pHrange of3.0-9.0, the catalytic activity did not change obviously when catalyst was reusedcontinuously5times, and the elution amount of Fe was below0.4mg/L, the elution amountof Mn was below0.2mg/L. Mechanism studies of heterogeneous Fenton reaction showed thathydroxyl free radicals were generated during the circulation was formed between Fe(III) and Fe(II) under the action of UV, so it was is a real heterogeneous reaction.Heterogeneous photo-Fenton process was applied to treat pulping wastewater after aero-bic treatment. The results showed that heterogeneous Fenton process was a effective way foradvanced treatment of pulping wastewater. Under experimental conditions of initial pH3.0,H2O2dosage2.5mL/L, catalyst dosage1500mg/L, temperature30℃, and reaction time150min, COD was degraded from about380mg/L to about65mg/L. When initial pH was5.0,reaction time wad180min, other things were equal, COD was degraded to below70mg/L,even when the pH was7.0, the catalytic activity was still high. The catalytic activity did notchange obviously when catalyst was reused continuously4times, and the elution amounts ofFe and Mn were very low.A method for COD rapid determination by the dual-wavelength spectroscopic methodwas established to eliminate the influence of H2O2for COD determination. The correlationequation between the absorbance and COD was COD173.57(A272A546)8.5577.Compared with the standard testing method, the precision and accuracy of the equation wasreliable. The method can be used for the rapid determination of COD in wastewater.A coupled coagulation-heterogeneous Fenton process was applied for the treatment ofpapermaking-reconstituted tobacco slice wastewater. The process conditions were optimizedby response surface method. Under the optimized conditions, COD was degraded to about63.5mg/L, decoloration was nearly100%. It could be concluded that this technology wassuccessful for the treatment of papermaking-reconstituted tobacco slice wastewater.GC-MS analysises of pulping wastewater and papermaking-reconstituted tobacco slicewastewater showed that organic compounds was greatly reduced, aromatics and organic chlo-ride were completely removed, most organic compounds were completely mineralized or de-graded into small molecular organic acids. |
PDF Full Text Request