| The lead tannic acid wastewater is generated during the production of lead tannic acid,washings and equipment wash water. The wastewater has a large CODCrvalue, and thewastewater are always high color, strong acidity, low biodegradability and extremelydifficult to deal with. It will cause serious groundwater pollution, and ultimately endangerhuman life, if not treated and directly discharged into the environment. Tannic acid caninhibit the respiration, metabolism and growth of many microorganisms such as algae,plankton and invertebrates by binding with protein and polysaccharides. Thus, theconventional biological method is not suitable for directly treating the tannic acid leadwastewater. This paper uses the combination of chelate precipitation and advancedoxidation method to treat tannin lead wastewater, explores the best operating parameters foreach treatment method, and analyses the reaction mechanism of each process.Firstly, the degradation effects of conventional treatment processes such as coagulation,extraction, adsorption and chelate precipitation method for the biorefractory organicwastewater were compared in this article. The analysis found that the chelate precipitationmethod enabled the removal of Pb2+precipitation, and could effectively remove the tannicacid ions. Secondly. The influencing factor for chelate precipitate process were furtherstudied on. The results showed that in the original wastewater pH conditions, the optimumoperating parameters were adding1.5g/L of chelate agents, mixing time20min, andultimately the CODCrand Pb2+removal percent were respectively50.8%and96.6%.General Fenton oxidation can effectively remove the CODCrand color in thewastewater, after pretreatment of chelate precipitation. The effects of initial pH value,n(H2O2):n(Fe2+) ratio, H2O2dosage and oxidation time were systematically investigated inthe Fenton reaction proess. The optimum operating parameters were initial pH of3, n(H2O2):n(Fe2+) ratio of12, H2O2dosage of3mL/L. Finally the CODCrremoval percentreached a maximum of82.6%, the CODCrcontent of water was down to150mg/L when theoxidation time was60min.Wastewater pretreated by chelate precipitate after conventional Fenton degradation, theCODCrof effluent still require further treatment. Then the combination of ultrasoniccavitation and Fenton was used to treat the wastewater and the influencing factors forwastewater degradation was systematically investigated. Ultimately the optimum operatingparameters of this method was determined that the initial pH of the water sample was3,H2O2dosage was2.5mL/L and n(H2O2):n(Fe2+) ratio was14. when the ultrasonicdegradation was60min, the CODCrvalue dropped below80mg/L, the effluent CODCrremoval percent reached a maximum of91.8%. However, the repeated tests found that thedegradation of the wastewater by this method was unstable, and the average CODCrremovalefficiency was only86.4%.To overcome the instability of the degradation of wastewater by Fenton strengthenedby ultrasonic cavitation, a combination of photocatalytic and Fentonfor wastewater was putforward. Photocatalytic technology was widely used in wastewater treatment because of itsnon-toxic, high catalytic activity and stable photochemical properties. The optimumoperating parameters of such a method were initial pH of4, H2O2dosage of2mL/L,n(H2O2): n(Fe2+) of20, TiO2dosage of2g/L, light intensity of500W. The CODCrremovalfor the wastewater percent was89.7%after60min of degradation.The economic analysis for the degradation of wastewater by conventional Fentonreagent method, Fenton method enhanced by ultrasonic cavitation andPhotocatalytic-Fenton showed that the actual processing cost per ton of waste (excludingequipment costs) are as follows:3.72yuan,3.36yuan and2.76yuan. Finally, the UV-visiblespectrophotometer was used to analysis the intermediates and by-products of tannic acidmolecules in advanced process, and it showed that: advanced oxidation process caneffectively destroy the molecular structure of tannin, resulting in many non-intermediatecolor. |
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