The Ultrasonic Degradation Of Phenolic Pollutants

With the development of global industrialization, the environment pollution is seriousincreasingly, due to the toxicity and refractory of industrial wastewater containing phenols, itsdegradation of phenols wastewater received widespread attention. And wastewater containingphenols pollution can happen at any place of the water supply system, so for the treatment ofphenols wastewater has become the common challenge faced by the world. Using ultrasonicdegradation of phenols pollutants, is a new type of water treatment technology developed inrecent years. This paper introduces the degradation mechanism of using ultrasound degradethe phenolic pollutants, and summarized the research progress of sonochemical degradation ofphenolic pollutant in recent years.In this paper use two combination methods: ultrasound synergy activated carbondegradation (US/AC) and ultrasound synergy Fenton-like reagent degradation(US/Fenton-like reagent), select phenolic pollutants: phenol, bis-phenol A, p-chlorophenoland p-nitrophenol as the research object. By ultraviolet-visible spectroscopy,high-performance liquid chromatography(HPLC), scanning electron microscopy(sem) methodto study the effect of degradation factors,intermediate, speculated the degradation mechanismand kinetics characteristics in the degradation process.By using the method of US/AC to degrade phenol, bis-phenol A and p-chlorophenol, andexperimental results show that there are synergistic effect in the process of the degradation,and that degradation effect is significantly. In the single factor experiments, studied thedosage of activated carbon, power, solution pH value, the reaction time and adding oxidant ondegradation effect. Under the condition of the best target pollutants degradation, the phenolicpollutant: phenol, p-chlorophenol, bis-phenol A were almost completely degrade (thedegradation rate were respectively: the phenol97.86%, the p-chlorophenol99.40%, thebis-phenol A99.11%)Through analyzing the degradation process of intermediate, phenol and p-chlorophenol’sdegradation mechanism were discussed preliminarily. Detected in the process of ultrasonic degradation of phenol, the intermediate were catechol,hydroquinone, maleic acid. And speculated that the degradation process of hydroxyl freeradicals, hydroxyl radicals generated attack benzene electrophilic addition reaction, and makethe phenol degradation completely. In the process of the sonochemical degradation ofp-chlorophenol, after oxidizing reaction hydroxyl radicals, the C-Cl bond rupture fromhydroquinone, and then the hydroquinone molecules continue to be oxidative decompositionof maleic acid. Dynamic analysis were performed for each of the degradation process,according to the result in the degradation of phenol, p-chlorophenol, bis-phenol A in themethod of US/AC, the degradation process of approximate pseudo-first-order kinetic process.Using the US/Fenton-like reagent degrade the p-chlorophenol and p-nitrophenol,discussed the influence of conditions on the degradation results, the conditions includingFenton-like reagent’s proportion, dosage, ultrasonic power, solution pH value and reactiontime. In single factor experiment and research the best degradation condition, thep-chlorophenol was degraded in20min, the rate can reach99.92%; the p-nitrophenol wasdegraded in120min, the rate can reach96.47%.Through analyze the intermediate generated in the degradation process, preliminaryexploration the degradation mechanism of using US/Fenton-like reagent method degradep-chlorophenol: under the acoustic cavitation effect of chlorine phenol molecules inside thecavitation bubble pyrolysis reaction remove chloride ion, and then under the action of a largenumber of hydroxyl radicals depth of oxidation reaction generated hydroquinone, thehydroquinone remove phenolic hydroxyl hydrogen ions generated benzoquinone, finallybenzoquinone and continue to be oxidation ring into organic acids. According to manyliteratures and the p-chlorophenol degradation mechanism, the preliminary estimate thep-nitrophenol’s degradation mechanism is as follows: in the process of p-nitrophenoldegradation under the action of the high concentration of hydroxyl radicals, remove nitro generate hydroquinone and generate further dehydrogenation benzoquinone, continue tobe open ring oxide into small molecular organic acid.In addition, the dynamic analysis were performed for each of the degradation process,according to the results in the use of US/Fenton-like reagent method degrade thep-chlorophenol and p-nitrophenol, various approximate pseudo-first-order kineticsdegradation process.