| m-cresol industrial wastewater usually contains kinds of toxic pollutants such as sulfuric acid, sodium bisulfate, m-cresol and m-toluidine, which make it characterized by high-concentrated acid, salts, organics and high toxicity. It has become a difficult problem of industrial wastewater treatment.Conventional technologies such as oxidation waste resources and reagents seriously. In this work, new technology of multistage resin adsorption was developed to recycle m-cresol, m-toluidine and sodium bisulfate respectively. Innovation points of the integrated technology was the online regeneration method of hypercrosslinked polymeric adsorbent, which realized desorption of m-toluidine and adsorption of m-cresol simultaneously. Therefore, the technology has advantages as high efficiency, low consumption and separate recycling, providing a new way to m-cresol industrial wastewater treatment.Hypercrosslinked polymeric adsorbent can separate and remove m-cresol and m-toluidine efficiently in different conditions. In adsorption based on physical effect such as hydrogen bond and hydrophobic effect, the adsorbate was mainly molecule. The ionization degree of m-cresol and m-toluidine was different at the same acidity-alkalinity, thus separation and respective recycling can be attained. When the concentration of sulfuric acid in wastewater reached 2 mol/Lor higher, the adsorption capacity for m-cresol reached 2.35 mmol/g while the adsorption capacity for m-toluidine was lower than 0.1 mmol/g. When pH=9, the adsorption capacity for m-toluidine was satisfactory. Coexisting inorganic salts improved the adsorption performance of hypercrosslinked polymeric adsorbent, the adsorption capacity for m-cresol and m-toludine increased 19.27% and 21.46% separately for promotion of salts by molecularization, hydrophobic effect and salting-out effect. The adsorption isotherm fitted Freundlich model better and equilibrium can be reached in 5 hours for both m-cresol and m-toluidine. The adsorption rate of m-cresol and m-toluidine has improved for 144.4% and 69.23% respectively in multicomponent system. In dynamic adsorption, when flow rate reached 5 BV/h for three-component m-cresol solution and under 293K, the initial 63 BV effluent complied with the Class A of Integrated Wastewater Discharge Standard (GB8978-1996). when adsorption rate reached 5 BV/h for m-toluidine solution, the breakthrough point reached 236 BV.The adsorption capacity of transformative ion exchange resin for sulfuric acid was positively associated with the concentration of acid. The maximum can be 1.88 mol/L. Coexisting inorganic salts promoted the acid adsorption while flow rate mainly had no effect on acid adsorption. Pure water was used as regenerate for desorption of sulfuric acid, dynamic regeneration result showed that the total recovery rate of initial 0.85 BV reached 64.4%, and the concentration of recycling acid was 62.82% of original concentration. When the volume of recycling solution increased to 4.5 BV, the COD recovery rate reached 75.87%. The lowly-concentrated recycling sulfuric acid can be used for next regeneration. The concentration of m-t toluidine in effluent was about 250 mg/L.According to the pH difference of adsorption and desorption of m-cresol and m-toluidine on hypercrosslinked polymeric adsorbent, based on the promotion for adsorption of coexisting inorganic salts, wastewater containing m-cresol was used as regenerate to obtain the on-line regeneration of resin preloaded with m-toluidine. The result indicated that regenerate containing m-cresol improved the stripping rate of m-toluidine. What’s more, the adsorption of m-cresol wasn’t inhibited by desorption of m-toluidine. Thus simultaneous adsorption of m-cresol can be attained, the investment cost was saved and the process cycle was shortened. In spite of the feeble inhibition for desorption of m-toluidine of inorganic salts, the results can be reversed by higher concentration rate and temperature. The desorption of m-toluidine and adsorption of m-cresol reached equilibrium in 2 and 4 hours separately. Original wastewater was used for on-line regeneration In dynamic adsorption, when flow rate was 2 BV/h and the temperature was 293K, the stripping rate of m-toluidine reached 90.08%, and the breakthrough point of m-cresol was 166 BV.In a word, when the multistage resins-combined separation technology and original wastewater online regeneration-simultaneous adsorption method was applied to treatment,0.48 kg m-cresol,3.39 kg m-toluidine and 139.20 kg sulfuric acid was recycled from 1 ton wastewater, the preliminary estimates of net earning was 142.59 yuan/t wastewater, showing obvious economic benefits. Compared to conventional unrecyclable methods and resin adsorption technology, the running cost was lower and the integrated technology cost less regents and energy. |
PDF Full Text Request