不同生产条件对微酸性电生功能水理化特性的影响（英）.pdf

第 28 卷第 19 期农 业 工 程 学 报Vol.28No.192322012 年10 月Transactions of the Chinese Society of Agricultural EngineeringOct.2012Effect of preparing condition on physicochemical property ofslightly acidic electrolyzed functional waterHou Yatao1,2,Li Fade1,2,Zhang Shifu1,2,Wang Lijun1,2,Liu Haijie3,Li Lite3,Ren Jie1,2(1.College of Mechanical and Electronic Engineering,Shandong Agricultural University,Tai an 271018,China;2.Shandong Provincial Key Laboratory of Horticultural Machineries and Equipments,Tai an 271018,China;3.College of Foood Science and Nutritional Engineering,China Agricultural University,Beijing,100083,China)Abstract:In order to obtain the best operating parameters for preparing slightly acidic electrolyzed functional water(SAEFW),a four-factor central composite design was adopted to investigate the effects of voltage(U),hydrochloric acidsolution flow rate(QH),concentration(CH)and water flow rate(QW)on the available chlorine concentration(ACC),pHvalue,oxidation-reduction potential(ORP)and electrical conductivity of SAEFW.The results indicated that the ACC wasaffected significantly(p0.01)by the processing factors,such as QW,U and CH.It was noticeable(p0.01)that the factorsQH,CHand QWinfluenced the pH value of SAEFW.QH,CHand QWobviously affected(p37%hydrochloric acid,analytically pure)with deionized water(DW).Thevoltage and flow rates of hydrochloric acid and freshwater(Table 1,Table 2)were respectively adjustedwith the correspondent control valve on SAEFWgenerator.Thegeneratorwasoperatedateachdesigned operation condition(Table 1,Table 2)for atleast 5 min to reach a steady state before the SAEFWsample was analyzed.The eight samples(volume:500mL)were collected in eight 500-mL beakers forfurther analysis at 5-minute intervals.1.3Analysis of the SAEFWThe pH value,the oxidation-reduction potential(ORP),the electrical conductivity and the availablechlorine concentration(ACC)of the SAEFW sampleswere measured immediately after collected.Thevalues of the pH value and the electrical conductivityofSAEFWweremeasuredwithaBenchtoppH/Conductivity Meter(Model 550A,Orion Research,Inc,USA),ranged from pH value 0-14 and 0 to 500mS/cm respectively.The values of the ORP was measured with a pH/mVMeter(PH value-2625，Qingdao,Shandong,China),ranged from 0 to 2000 mV.The ACC was measuredaccording to the iodometric method28.1.4Experimental design and statistical analysisA four-factor central composite design wasadopted in this study to investigate the effects of thevoltage,the hydrochloric acid solution flow rate,thehydrochloric acid solution concentration and the freshwaterflowrateonthephysicalandchemicalproperties of SAEFW29.The work of SAEFWgenerator was steady at every designed condition inthe central composite design(Table 1,Table 2).Datafrom each experiment was collected and analyzed byanalysis of variance tests and regression analysis.Table 1Factors and levels used in the factorial designLevelsFactors(-2)(-1)(0)(+1)(+2)U/V34.0056.007QH/(L h-1)0.690.861.031.201.38CH/%1.002.003.004.005.00QW/(L h-1)60120180240300Note:U is voltage;QHis hydrochloric acid solution flow rate;CHishydrochloric acid solution concentration;QWis water flow rat;(Same asbelow).Table 2Design of response surface analysis experimentRun numberU/VQH/(L h-1)CH/%QW/(L h-1)ACC/(mg L-1)pH valueORP/mV/(S cm-1)150.6906318042.54 1.646.23 0.09933 61155 17251.3762318057.87 0.983.36 0.161121 121472 14331.0334318024.19 1.215.81 0.04946 31252 4451.0334330025.64 0.586.46 0.02902 31257 2551.0334318047.19 1.436.08 0.05941 31281 11651.0334118025.05 0.436.62 0.03890 81187 22741.2048412069.23 1.732.43 0.051180 22893 28851.0334318053.30 1.566.18 0.06936 51384 13961.2048224036.62 1.346.19 0.02929 61177 281060.8620212062.42 1.046.05 0.07942 41234 71161.2048424052.64 0.825.74 0.09960 71245 81261.2048212070.24 0.995.62 0.08971 31278 31351.0334318043.37 2.346.40 0.09929 71176 151471.0334318054.92 1.666.08 0.04944 21295 41541.2048212048.08 1.615.48 0.11976 61333 81651.0334318045.32 3.685.92 0.12931 81294 171751.0334318049.95 4.525.85 0.03955 111243 121840.8620212040.06 2.116.16 0.08932 71283 111951.0334318051.65 1.985.72 0.08960 61347 192051.0334360118.84 1.342.65 0.121177 72311 242160.86204120120.90 1.422.78 0.071163 51990 232240.8620412055.24 1.372.80 0.081156 72045 282340.8620224018.99 0.826.44 0.06894 71236 5第 19 期侯亚涛等：不同生产条件对微酸性电生功能水理化特性的影响235ContinuedRun numberU/VQH/(L h-1)CH/%QW/(L h-1)ACC/(mg L-1)pH valueORP/mV/(S cm-1)2441.2048424029.32 1.265.70 0.10956 61310 172560.8620224033.38 1.53627 0.06917 61221 142660.8620424052.64 1.506.16 0.03926 31206 32740.8620424025.94 1.306.02 0.15914 71222 122851.0334518064.25 0.982.82 0.061156 41863 232941.2048224021.73 0.536.29 0.08905 81260 53061.20484120105.19 1.352.47 0.031185 12753 13Note:ACC is available chlorine concentration;ORP is oxidation reduction potential;is electrical conductivity.2Results and discussionsAccording to the results of ANOVA for theresponse surface quadratic model listed in Table 3 andTable 4,it was found that the regression models forfour parameters of SAEFW were significant(p0.05)and the“Adequate Precision”ofevery regression model was more than 4,which meansthefittingdegree and confidence ofregressionequationswerehigh,thusthebestoperatingconditions could be well predicted by the fourregression models.Table 3Variance analysis of quadratic response surfaceregression modelSourceP-ValueACCP-ValuepHP-ValueORPP-ValueLinear0.0001*0.0001*0.0001*0.0001*Quadratic 0.0001*0.0002*0.0002*0.0011*Cross-product0.0081*0.0002*0.0001*0.0001*Lack of fit0.06080.11530.05160.0542Total effectVoltage 0.0001*0.79420.52630.5637Hydrochloricacid flow rate0.12700.0003*0.0002*0.0022*Hydrochloricacidconcentration 0.0001*0.0001*0.0001*0.0001*Water flow rate 0.0001*0.0001*0.0001*0.0001*Ranges18-121 mg L-12.43-6.62889-1185 mV1154-2893 S cm-1Note:*significantly different at =0.05 level;*significantly different at =0.01 levelTable 4ANOVAfor response surface quadratic modelSourceACCpH valueORPMode P-Value0.00010.00010.00010.0001R-Squared0.96380.96510.97020.9561Adj R-Squared0.92990.93250.94240.9151Pred R-Squared0.80760.82010.84100.7658Adequate Precision20.08917.23018.98416.895Equation in Terms of Actual Factors:ACC=48.46+11.95U+2.26 QH+10.75 CH20.27QW2.05 U QH+4.86 U CH4.18 U QW1.26 QHCH0.3 QHQW5.00 CHQW2.06 U2+0.60 QH20.79 CH26.11 QW2（1）pH value=6.03+0.021 U 0.35 QH0.92 CH+0.94 QW+0.017 U QH+0.028 U CH0.00875 U QW0.005 QHCH+0.051 QHQW+0.70 CHQW+0.006458 U20.28 QH20.30 CH20.34 QW2（2）ORP value=942+3.17 U+24.75 QH+62.75 CH68.92 QW1.5 U QH1.5 U CH+2.88 U QW+1.62 QHCH1.25 QHQW47 CHQW1.67 U2+18.83 QH2+17.83 CH2+21.96 QW2（3）=1278.49 16.33 U+101.91 QH+249.74 CH293.32 QW13 U QH4.63 U CH+7.5 U QW+104 QHCH99.87 QHQW279 CHQW+7.98 U2+17.98 QH2+70.85 CH2+135.6 QW2（4）Note:U is the voltage,V;QHis the hydrochloricacid solution flow rate,L/h;CHis the hydrochloric acidsolution concentration,%;QWis the water flow rat,L/h;ACC is the available chlorine concentration,mg/L;ORPis the oxidation reduction potential,mV;is theelectrical conductivity,S/cm.2.1Effects of processing parameters on availablechlorine concentration(ACC)of slightly acidicelectrolyzed functional water(SAEFW)The available chlorine concentration(ACC)wassignificantlyinfluencedbythevoltage,thehydrochloric acid solution concentration and the waterflow rate(Table 3).The ACC increased with theincreaseofthehydrochloricacidsolutionconcentration(Fig 2-3),which led to the concentrationof chloride ions to increase,so that more chloride ionsmoved to the anode to lose electrons and becamechlorine gas easily.However,when the hydrochloricacidsolutionconcentrationwastoohigh,theincreasing rate of ACC became lower,due to a lot of农业工程学报2012 年236the chlorine gas bubbles generated on the surface ofelectrode,whichpreventedelectrolytesfromcontacting the electrodes.In this case,the generatorcould reach the maximum capacity of electrolysis cell,so the maximum of ACC was achieved.This wassimilar to the results reported by the study26whichreported that the ACC increased with the increase ofthe sodium chloride solution concentration,but asteady maximum ACC would be achieved as thesodium chloride solution concentration was over acritical concentrate,thus the electrolysis reachedmaximum capacity of the electrolyzed oxidizing watergenerator.Ifthehydrochloricacidsolutionconcentration continued to increase,the pH value ofFig.2Response surface plots of available chlorineconcentration(ACC)of SAEFW with respect to water flow rate(QW)and hydrochloric acid solution concentration(CH)(atU=5 V,QH=1.03 L h-1)Fig.3Response surface plots of available chlorineconcentration(ACC)of SAEFW with respect to hydrochloricacid solution concentration(CH)and voltage(QW=180 L h-1,QH=1.03 L h-1)Fig.4Response surface plots of the available chlorineconcentration(ACC)of SAEFW with respect to the water flowrate(QW)and the voltage(CH=3%,QH=1.03 L h-1).the SAEFW could decrease further.When the voltage,the hydrochloric acid solution concentration and thehydrochloricacidsolutionflowratewerekeptconstant respectively,the amount of the chlorine gasgenerated in the electrolysis cell was constant,whichresulted in the ACC decreasing with the increase ofthe water flow rate(Fig 2,4).Similarly,the study29reported that the ACC increased with decreases ofwater flow rate.The higher voltage resulted in thehigher electric field intensity in the electrolysis cellcausedmoreintensiveelectrochemicalreactionoccurred on the surface of the electrode becameintensive,which in turn resulted that the more chlorideions could lose the electrons from anode to becomechlorine gas.Thus the ACC increased with theincrease of the voltage(Fig.3-4).This effect wasconsistent with a study30which found that the ACCincreased with increases of the voltage.Therefore,theACC increased with the increase of the voltage andthe hydrochloric acid solution concentration.On theother hand,with the increase of the water flow rate,the ACC decreased.2.2Effects of processing parameters on pH valueof slightly acidic electrolyzed functional water(SAEFW)The pH value of SAEFW was significantlyaffected by the hydrochloric acid flow rate,thehydrochloric acid solution concentration and the waterflow rate(Table 3).As shown in Fig.5 to Fig.7,itwasconfirmedthatthepHvalueofSAEFWdecreased with the increase of the hydrochloric acidsolution concentration and the hydrochloric acid flowrate,but increased with the increase of water flow rate,when the voltage kept constant.It was due to that theelectrochemical reacting intensity would keep steadybecauseoftheconstantvoltage,althoughtheconcentrate of the hydrogen ion would increase withtheincreaseofthehydrochloricacidsolutionconcentration.Ontheotherhand,whenthehydrochloricacidflowrateincreased,theelectrochemical reaction time in the electrolysis cellreduced,which resulted in that the less hydrogen ionscould move to the cathode to join the electrochemicalreaction occurred on the surface of the cathode,moreover,the amount of hydrogen ions flowing fromthe electrolytic cell increased in the unit time due tothe increase of the hydrochloric acid flow rate,so thatthe pH value of SAEFW decreased.As shown in Fig.6 and Fig.7,the pH value of SAEFW would increasewith increases of water flow rate due to the dilution ofwater.第 19 期侯亚涛等：不同生产条件对微酸性电生功能水理化特性的影响237Fig.5Response surface plots of pH value of SAEFW withrespect to hydrochloric acid solution concentration(CH)andhydrochloric acid solution flow rate(QH)(at U=5 V,QW=180 L h-1)Fig.6Response surface plots of pH value of SAEFW withrespect to water flow rate(QW)and hydrochloric acid solution(QH)flow rate(at U=5 V,CH=3%)Fig.7Response surface plots of pH value of SAEFW withrespect to water flow rate(QW)and hydrochloric acid solutionconcentration(CH)(at U=5 V,QH=1.03 L h-1).2.3Effects of processing parameters on oxidation-reductionpotential(ORP)ofslightlyacidicelectrolyzed functional water(SAEFW)It was listed in Table 3 that the ORP value of theSAEFWwassignificantlyinfluencedbythehydrochloric acid solution concentration and the waterflow rate.The value of ORP was determined by theconcentration of hydrogen ions and ACC16.Fig.8showed that the ORP value of SAEFW increased withtheincreaseofthehydrochloricacidsolutionconcentration and the hydrochloric acid flow rate,butdecreased with the increase of the water flow rate.Thereason for these phenomena was that with a constanthydrochloric acid solution concentration,the hydrogenion concentration and the ACC in the SAEFW woulddecrease with the increase of the water flow rate,which caused the ORP of the SAEFW decreasing.This was similar to the results reported by the study31who found that the ORP decreased with increases ofthe water flow rate.On the contrary,when the waterflow rate kept constant,the hydrogen ion concentrationand the ACC in the SAEFW would increase with theincrease of the hydrochloric acid solution concentrationand the hydrochloric acid flow rate,resulting withincreased the ORP of SAEFW.Similarly,the paper32reported that ORP was affected significantly by thesodiumchloridesolutionconcentration.Fig.8Response surface plots of oxidation-reduction potential(ORP)of SAEFW with respect to water flow rate(QW)andhydrochloric acid solution concentration(CH)at U=5 V,QH=1.03 L h-1).Fig.9Response surface plots of electrical conductivity ofSAEFW with respect to water flow rate(QW)and hydrochloricacid solution concentration(CH)(at U=5 V,QH=1.03 L h-1)2.4Effects of the processing parameters on theelectricalconductivity()ofslightlyacidicelectrolyzed functional water(SAEFW)As listed in Table 3 and shown in Fig.9,theelectrical conductivity of SAEFW was significantlyaffected by the hydrochloric acid solution concentrationandthe waterflowrate.The concentration ofhydrogen and chlorine ions determined the electricalconductivity of SAEFW.The electrical conductivityof SAEFW increased with the increase of thehydrochloricacidsolutionconcentration,butdecreased with the increase of the water flow rate.This study showed the similar result with the paper29农业工程学报2012 年238who reported that the electrical conductivity ofelectrolyzed oxidizing water increased linearly withincreases in sodium chloride solution concentration ofthe input(anode-side)solution.The reason for thesephenomena was that when the hydrochloric acidsolutionconcentrationwasconstant,theionconcentration in the SAEFW would decrease with theincrease of the water flow rate,which resulted that theelectrical conductivity of the SAEFW decreased.Onthe contrary,when the water flow rate kept constant,the ion concentration in the SAEFW would increasewith the increase of the hydrochloric acid solutionconcentration and the hydrochloric acid flow rate,which resulted in that the electrical conductivity of theSAEFW increased.2.5Best operating conditions for manufacturingSAEFW by generatorThe Design Expert software was used in thestudytogetthebestoperatingconditionsformanufacturing the SAEFW.In some references9,16,33,the criteria of 5.5pH value900 mVand ACC of 30-40 mg/L have been referred to b