Study On Electro-coagulation Treating Dyeing And Pharmaceutical Wastewater With Al/Fe Periodically Reversing

Along with the fast development of pharmaceutical and dyeing industry, a typical feature of global water pollution caused by the mass production of various organic substances has become an urgent problem to be solved in the field of environmental protection. According to the traditional electro-coagulation technology in power consumption of large, plate passivation, paper puts forward electro-coagulation with Al/Fe periodically reversing treating dyeing and pharmaceutical wastewater through using periodic reversing of switching modes and using synergistic effect of iron, aluminum cationic. A series of studys on treatment effect, reaction mechanism, degradation pattern, plate passivation, reaction kinetics and technical feasibility were carried out. The result was analyzed by combining of theoretical basis, monitoring data and apparent phenomenon. The following innovation achievements can be drawn from the study as following:(1) Reactive Black KN-B and Reactive Brilliant Orange X-GN were chosen for the feasibility study of electro-coagulation with Al/Fe periodically reversing treating dyeing wastewater.The result shows that system of electro-coagulation with Al/Fe periodically reversing treating dyeing wastewater is stable feasible.The efficiency of decolorization and COD value from200mg/L reactive black KN-B simulating organic wastewater are up to99%and55%respectively as the optimal operating conditions is that the ideal reaction time is30min, reaction voltage is10V, distance between electrodes plate is1.0cm, alternating period is10s and stirring speed is1000r/min, electrolyte concentration is O.OlOmol/L Na2SO4and initial pH value is5to11. By contrast, the efficiency of decolorization and COD value from200mg/L Reactive Brilliant Orange X-GN simulating organic wastewater are99%and74%respectively as the optimal operating conditions is that the ideal reaction time is20min, reaction voltage is9V, distance between electrodes plate is1.5cm, alternating period is8s and stirring speed is500r/min, electrolyte concentration is0.010mol/L Na2SO4and initial pH value is5to7. These results illustrated that the removal of Reactive Black KN-B requires relatively more harsh process conditions in comparison with Reactive Brilliant Orange X-GN.(2) Taking Reactive Black KN-B for example, the machnism on electro-coagulation with Al/Fe periodically reversing treating dyeing wastewater.The results shows that: reduction of ferrous and its multihydroxy compounds and the flocculation of metal flocculants with the contribution rates80%and18%respectively for decolorization,and flocculation of metal flocculants dominates the COD removal. According to a study comparing the different electrode materials (Al, Fe and graphite) and different power supply pattern (periodically reversing and DC), aluminum and iron bipolar electrodes periodically reversing electro-coagulation method shows the optimal treatment effect on dyeing wastewater because of aluminum, iron ion synergistic action helping to remove pollutants. SEM photos and elements spectral diagram of the plates before and after use reveal that periodically reversing mode effectively relief the surface passivation of the aluminum plate. The decolorization and COD removal of200mg/Lsimulating dyeing wastewater treated by using electro-coagulation with Al/Fe periodically reversing follows the first order reaction.(3) Berberine simulating pharmaceutical wastewater successfully treated by using electro-coagulation with Al/Fe periodically reversing method is further proof of the application feasibility on pharmaceutical wastewater treatment. The experiment results show that the efficiency of decolorization and COD value from the simulating organic wastewater are respectively up to99%and95%under the optimal conditions of the ideal reaction time is60min, reaction voltage is6V, distance between electrodes plate is0.3cm-0.6cm, alternating period is10s and stirring speed is750r/min, electrolyte concentration is0.015mol/L and initial pH value is3～10. During the process, the contribution rate of berberine molecules removal by air floatation and flocculation of the aluminum and iron ions formed inorganic flocculants are8%and70%where oxidation contributes about18%. The intermediate products of oxidation reaction remain in the solution. The decolorization and COD removal of200mg/L and400mg/L-1000mg/L berberine simulating organic wastewater treated by using electro-coagulation with Al/Fe periodically reversing can be both described by apparent first order reaction and zero order reaction kinetics respectively.(4) In chloramphenicol simulating pharmaceutical wastewater treatment study, chloramphenicol molecules are firstly oxidized to degradable organic compounds which increased the COD value of effluent and cause a fail of COD removal. Therefore, a combined periodically reversing-Fenton method is investigated. By adding1mL H2O2in order to increase the yields of hydroxyl free radicals, the removal efficiency of COD of chloramphenicol simulated wastewater is about30%with reaction voltage of8V, alternating period of10s, plate spacing of0.6cm and reaction90min.Combined with the basic principle of electro-coagulation, and reactive black KN-B, berberine as representative, reaction way of electro-coagulation with Al/Fe periodically reversing removing azo dye and ionic organic from dying wastewater and pharmaceutical wastewater were preliminarily determined. Furthermore the application of electro-coagulation with Al/Fe periodically reversing treating dyeing and pharmaceutical wastewater is preliminary realized.