Studies On Forming Law Of Hydroxyl Radical During Electrolysis And Treatment Of Wastewater With Organic Pollutants

Wastewater with organic pollutants is one of the most harmfulsubstances, because its characteristics of big volume, highconcentration, noxious to living beings, hard degradable by naturalprocesses and easy accumulated in bodies. Forming law of hydroxylradical during electrolysis process was discussed in this paper. Thentook wastewater with phenol for example, we described some factorsthat affected forming of hydroxyl radical, which further affectedphenol degradable effect.Hydroxyl radical is the main specie of many free radical oxidationreactions. The strong oxidation ability of hydroxyl radical can be usedto oxidize organic substances and other impurities in water, decreasesthe Chemical Oxygen Demand (COD) value and achieves the goal ofwater treatment. Aromatic hydroxylation from the reaction betweenhydroxyl radical and salicylate or its related compounds has been oftenutilized as a marker for the generation of hydroxyl radicals. We hadinvestigated several technical aspects of applying this method to studyhydroxyl radical production during electrolysis using the salicylicacid(2-HBA) to form 2,5-dihydroxybenzoic acid(2,5-DHBA).Aqueous solution of 2-HBA was electrolyzed by Ti-base Lead DioxideElectrode regard Sn, Sb as the intermediate level, then the solutioncontaining 2-HBA and 2,5-DHBA was analyzed by High PerformanceLiquid Chromatography(HPLC) with fluorescence detection .It wasconcluded that the oxidation of 2-HBA to 2,5-DHBA could be areliable and accurate indicator for the formation of hydroxyl radical ifthe experiments are well designed to avoid potential pitfalls associatedwith technical difficulties of the method. The results show that the pHvalue and frequency play important roles in the producing rate ofhydroxyl radical. High pH value is better than low pH value, also ishigh frequency than low frequency. The experiment of phenoldegradation was done at the same time;it indicated that using thehydroxyl radical produced by electrolysis to treat organic wastewatershave good effect.Because the degradation of phenol was achieved by hydroxylradical which formed by electrolysis, factors which affect hydroxylradical forming affect phenol degradation, too. Within the factorsdiscussed in this paper, high pH, high temperature was propitious tophenol degradation. On opposite, low pH, low temperature, theexisting of CO32-and PO43-went against phenol degradation. Theexisting of Cl-was propitious to phenol degradation, but went againstCOD removal.Through comparison of different initial phenol concentrations, wefound electrolysis efficiency was increased along with increasing ofinitial phenol concentrations. So this method was appropriate aspretreatment to other methods. Take it as advanced treatment wassuitable, too. Subsequently, the degradation of true wastewaterindicated that using this method to treat organic wastewaters has greatrealistic meanings and wide application prospects.