Treatment Of Phenol Wastewater By Granular Activated Carbon (GAC) Adsorption-Microwave Induced Oxidation Process

Microwave Induced Oxidation Process (MIOP) with Granular Activated Carbon (GAC) as catalyst and GAC adsorption-GAC regeneration under microwave irradiation were introduced into the treatment of phenol wastewater. Furthermore, corresponding theoretical investigation was performed. Upon the basis of adsorption of organic pollutants on GAC and intensive absorption of MV by GAC, organic pollutants were decomposed and carbonized under microwave irradiation.Firstly, this paper was concentrated on the treatment of phenole wastewater, MIOP with GAC as catalyst was established. Through the experiment it concluded that the removal rate of phenol was over 96% under the optimal treatment conditions: 50ml phenol wastewater of 68.5mgL-1; pH<9, GAC addition amount of 2.0g; 10min under MV of 100W. When phenol wastewater concentration was up to 420mg·L-1, the removal rate of phenol reached about 85%. After six times repeated utilization of GAC, the removal rate of phenol was still above 80%. Kinetics of phenol wastewater treatment was studied and the results showed that the process was fist-order kinetics reaction, the kinetics rate constant k= 0.3231 min-1, the half-life period t1/2= 2.15 min. It concluded that MIOP decomposed phenol completely from contrastive experiments and the ultraviolet spectra of phenol before and after MW irradiation.And then, aimed at organic wastewater of certain chemical plant in Jilin, GAC adsorption and GAC regeneration under microwave irradiation were established. Through experiment, it indicated that JX-206 fruit shell carbon was provided with the best wastewater treatement effect, the removal rate of COD was 90.17% and adsorption equilibrium was reached after 2h treatment under the optimal adsorption process: 1000mL wastewater; pH=3; GAC addition amount of 30.0g. After nine times repeated utilization of GAC, the removal rate of COD was still about 80%. Modified Freundlich adsorption isotherm model could be used to formulate the adsorption behavior of organic pollutants on GAC quantificationally. Iodine values of the regenerated GAC could reach about 900mg·g-1, the mass loss of GAC is less than 2% resulted from combustion under the optimal GAC-regenerated conditions: 1.67min under microwave irradiation of 400W; 600℃of GAC surface temperature.Based upon process research, the theory research of GAC adsorption-GAC regeneration under microwave irradiation was performed. Phenol adsorption kinetics rate constant ka, activation energy E and liquid effective diffusion coefficient Di of GAC adsorption under different conditions were estimated. Besides, standard free energy△G0,enthalpy△H0 and entropy△S0 of adsorption were calculated from Langmuir parameters. The results showed that when pH=5.35 and pH=10.30,△G0<0. However, the molecules of phenol may be adsorbed vertically, when pH was lower, ka, Di, adsorption amount and heat emission were higher, and E smaller. In this process the molecules of phenol may be adsorbed vertically, heat emission was higher, entropy enhancement lower. As result of intensive absoption of microwave by GAC, GAC surface temperature could reach to 1000℃, water- contained content increased from 54% to 15% under 2min MV irradiation of 600W. Moreover, temperature rising behavior could be described approximately quantificationally with experienced equation T=c1×exp(c2/t). Compared with GAC before microwave irradiation, after microwave irradiation pH of GAC surface increased from 4.82 to 6.82, the specific area and pore volume of regenerated GAC both increased 100%, microwave play a major role in GAC with pore less than 5nm.