Enhanced Degradation Of2,4-Dichlorophenol In Aqueous Solution Based On Zero-valence Aluminum Coupled With Microwave Irradiaion

The high reducibility of zero-valence metal is progressively harnessed anddeveloped by wastewater treatment researches. Since it’s characteristics ofhigh-effective, low-toxicity, source available, easily manipulated, wide applicationare emerged in treating waste water like dye, electroplating, or clorine-containedorganic wastewater and zero valence iron is most representative. However, fromprevious researches, zero valence aluminum is easier to produce active oxygen, moreresistive to precipitation in its3+state, and has higher electron-driven power（E0=-1.677V） compared to zero valence iron. Because of that, zero valencealuminum stand out with its distinctive advantages and potential. Nowadays, somestudies were performed by using the zero valance aluminum to degrade biphenol A,4-Chlorophenol in water body and good removal efficiency was achieved.Microwave refers to electromagnetic wave which wavelength ranges from1mm-1m and frequency ranges from300MHz-300GHz, respectively. Due toselectivity of microwave, it has broad application in chemistry. As to environmentalprotection, for example, the radiation of microwave rapidly kills the toxic and harmfulmicroorganisms and at the same time, the sensitizer which absorbs the microwaveintensively, could induce and catalyze nonbiodegradable reactions by generatingthe”hot point” which has high chemical activity under microwave radiation. Hence,the microwave technology attracts more concerns in environment related fields andgradually be employed in treatment of pollutants in the water, the air like nitric oxide,sulfur oxide, and the soil like polybrominated bipheny.In this experiment, zero valence aluminum and the selective heating ofmicrowave was combined, and the effect on removal efficiency of aqueous2,4-dichlorophenol utilizing inducing catalysis was investigated. Besides, degradationbyproducts and reaction mechanisms was studied and analyzed. The results shownthat, the microwave radiation strengthen the removal effects on removing2,4-dichlorophenol and the speed of degradation is improved significantly. Beforeintroducing the microwave radiation, the optimal dosage for zero valence aluminumwas2.0g, the optimal reaction temperature was50℃, the optimal pH was2.5. Whenthe reaction time was4h, the aqueous solution was50ml, the concentration of2,4-dichlorophenol was100mg/L, the removal efficiency reached to the maximumwhich was51.52%. The removal efficiency kept increasing as the increasing of the dosage of zero valence aluminum or the temperature but kept decreasing as theincreasing of pH under the experimental condition. Under the acidic condition, zerovalence aluminum reacts with dissolved oxygen and produce H₂O₂which furtherreacts with and transfer electron, producing hydroxyl radical which reacts with2,4-dichlorophenol in the aqueous solution and therefore2,4-dichlorophenol isremoved. When the dosage of zero valence aluminum was2.0g, the aqueous solutionwas50ml, the concentration of2,4-dichlorophenol was100mg/L, irradiating theaqueous solution for300s using700W radiation power, the removal efficiency was ashigh as97.50%and the removal efficiency kept increasing as the increasing of thedosage of zero valence aluminum or the power of microwave. The degradationproducts of inducing catalysis by microwave include like β，β’-bichlorinated ethyl,4-chlorphenol, styrene,2-chlorophenol and phenol, most of which are going throughdechloridation and ring-opening processes.