Study On Removing Phenol From Geothermal Water And The Generation Characters Of Phenol Oxidation By-product

Geothermal water is an important water resources and energy, development and utilization of geothermal water is conducive to alleviate the current energy and the shortage of water resources situation. Phenol pollutants in geothermal water may seriously affect the development and utilization of geothermal water, there is a serious harm to human health, in order to ensure safety in development and utilization of geothermal water, phenol must be removed from geothermal water.Effect and influencing factors on the removal of phenol in using chlorine dioxide oxidation, activated carbon adsorption, and chlorine dioxide-activated carbon hyphenated technique was studied, and the generation characteristics of by-product for phenol oxidation by chlorine dioxide was examined.The test results of phenol oxidation by chlorine dioxide show that the:as the simulated water samples, at temperature45℃, concentration of phenol0.2mg/L, chlorine dioxide dosage of0.6mg/L, reaction time30min, the solution pH=8, the phenol removal efficiency can reach93%, decreasing the solution pH, is conducive to the removal of phenol; for the geothermal water sample, the reaction temperature is45℃, phenol concentration0.2mg/L, chlorine dioxide dosage at1.0mg/L, reaction time60min, solution of pH≤8, the removal rate of phenol for a minimum is92%, prolonging the reaction time on the removal of phenol had little effect, when pH>8, the phenol removal rate decreased obviously.Test generation character of by-product in chlorine dioxide oxidation phenol process was studied:the main oxidation by-product such as p-benzoquinone, chlorite and chlorate was selected, and the yield of by-product in different conditions was studied. Results show that:the effect of dosage of chlorine dioxide and solution pH on the formation of by-products is relatively large, the reaction time is greater than or equal to30min, yield of the chosen three by-product does not increase; p-benzoquinone formation rate increased with increasing chlorine dioxide dosage, p-benzoquinone yield is50-70%, when the chlorine dioxide and phenol mass ratio is greater than2.5, the production of p-benzoquinone basic stability, and had the trend of decline; production of chlorite and chlorate salt increases with the increase of chlorine dioxide dosage, the chlorite and chlorate yield were30-65%and5-10%,respectively. When the pH value increased from3to8, amount of p-benzoquinone formed gradually increased, when pH>8, the removal efficiency of phenol decreased obviously, generating amount p-benzoquinone started to decrease; and amount of chlorite and chlorate increased with the increase of pH value. In chlorine dioxide oxidation process, the control conditions for the formation of by-products is:dosage and phenol quality of chlorine dioxide solution is larger than2.5, pH≤8, reaction time with30min.The results of activated carbon adsorption test show that:activated carbon has good adsorption effect on phenol, when the phenol concentration is0.2mg/L, temperature45℃, reaction time2h, the dosage of activated carbon6g/L, pH=6.5, the removal rate of phenol was95%. The thermodynamics of adsorption results show that:thenactivated carbon adsorption process of phenol was better agreement with Freundlich adsorption isothermal equation, the thermodynamic parameters k=2.7,1/n=1.0293. The adsorption kinetics results showed that:activated carbon adsorption for phenol can use the pseudo two order reaction kinetics model to express, the kinetic constant k2=4.0991g.mg-1.min-1. Activated carbon fixed bed dynamic penetration curve showed that, under the same external conditions, the fixed bed breakthrough time is greatly affected by the water flow, water flow is larger, the shorter the breakthrough time.Chlorine dioxide-activated carbon hyphenated technique was used to remove phenol and the oxidation by-product, the result show that:Chlorine dioxide dosage of1.0mg/L, reaction time60min, the oxidation reaction effluent with20ml/min flow through a fixed bed of activated carbon, in the final effluent, the phenol removal rate up to99%, the maximum removal rate of benzoquinone50%, chlorite remove rate is100%; when the flow rate is35ml/min, phenol the highest removal rate is98.5%, the maximum is30%on the removal of benzoquinone, chlorites removal rate is76%; the different water flow has obviously effect on breakthrough time of the activated carbon fixed bed:when the inlet water flow is35ml/min, the breakthrough time of activated carbon fixed bed is10h, when the inlet water flow is20ml/min, breakthrough time for activated carbon fixed bed is16h. Chlorine dioxide-activated carbon adsorption combined process for phenol removal are better than using activated carbon adsorption or chlorine dioxide oxidation alone, but also has obvious control effect of phenol oxidation by-products.