Experimental Investigation Of Electrochemical Oxidation Of Organic Wastewater On Boron-doped Diamond Anode

Treatment of refractory organic wastewater has been a research focus of scholars.Organic wastewater (mustard tuber wastewater and landfill leachate) with highconcentration, strong toxicity and bio-refractory contaminants could pollute serioussurface water, groundwater and its surrounding environment, if processing isundeserved. Main treatments of organic wastewater are Physical methods, Chemicalmethods, Biological methods and combination of these methods. However, physicalmethods and chemical methods are too easy to cause secondary pollution. Because of itseconomy, biological method is more popular, but it is not efficient for the abatement ofbio-refractory organic matters. Electrochemical oxidation method has the advantages ofgood treatment effect, no sludge generated, easy to management, without adding a smallamount of chemicals and no secondary pollution in the treatment of bio-refractoryorganic contaminants. It is a kind of environment-friendly advanced oxidationtechnology and has attracted more and more attention.In recent years, boron-doped diamond (Boron-doped diamond, hereinafter referredto as BDD) thin film electrodes have attracted much closer attention due to its excellentphysical and chemical properties. This paper constructs two-electrode system for theelectrochemical oxidation of phenol wastewater, tuber mustard wastewater and landfillleachate on a boron-doped diamond (BDD) anode. This study investigated the effects ofseveral operating parameters on the removal rate of pollutants of two kinds of organicwastewater, such as dilution ratio (initial concentration), applied current density, initialpH, electrode gap and concentration of the supporting electrolyte, using the single factorexperiment and the optimum operating conditions were determined. And the optimaloperating conditions for the treatment of the former concerned wastewater weredetermined. Experimental results showed that the effects of current density and dilutionratio was greater on the electrochemical oxidation performance, however, intial pHvalue and electrode gap had a little effects on the anodic performance.When the initial phenol concentration was100mg/L, the optimal operatingcondition of electrochemical oxidation of phenolic wastewaster is current density of55mA/cm2, no adjustment of pH, supporting electrolyte (NaCl) concentration of5g/Land electrode gap of10mm, removal efficiency of COD and phenol was91.11%and86.78%, respectively. The optimal opertating condition of anodic oxidation of mustard tuber wastewater on BDD anode was determined as follow: the dilution ratio of1:2, thecurrent density of50mA/cm2, no adjustment of the initial pH, electrode gap of15mm.The removal rate of COD and NH3-N was98.35%and99.68%, respectively, during theelectrolysis time of4h. The removal rate of COD is followed by y=0.435t with R2valueof0.9899. And the removal rate of NH3-N is followed by y=0.53+0.936t+0.031t2-3.46×10-4t3with R2value of0.9956. The optimal operating condition of electrochemicaloxidation of landfill leachate was dilution ratio of1:2, current density of75mA/cm2, noadjustment of initial pH, electrode gap of10mm. After the treatment of9hours, theremoval rate of COD and ammonium was99.13%and99.95%, respectively. And thecorresponding energy consumption was91.46kWhkgCOD-1. Both of the concentrationof COD, TOC and NH3-N are following by linear function of y=1675.3-3.1t,y=532.8-0.686t and y=1296.0-2.5t, respectively. And the corresponding R2were morethan0.99. The current efficiency decreased with the electrolysis time.