Removal Of Malachite Green From Aqueous Solutions By Electrocoagulation/Adsorption Coupling Method

The treating of dye wastewater is a hot issue in our country because of the large amount and backward method.Electrocoagulation(EC)technology has many advantages such as simple equipment,environmental friendly,and easy to automatic control.But it also has some shortcomings such as the high energy consumption.In this paper,an electrocoagulation/bio-adsorbent adsorption coupling technique was raised to remove malachite green(MG)from aqueous solution in shorter time and lower energy consumption.In this paper,peanut shell(PS)and Na OH modified rice husk(Na OH-RH)were prepared and characterized by SEM,BET,FTIR,and p Hpzc were also measured.The results showed that both adsorbent have good adsorption property,and the appropriate p H for MG adsorption were: peanut shell:p H>5.8 and Na OH modified rice husk: p H>7.4.The effect of current density,dose of peanut shell,initial solution p H value,and initial concentration of malachite green were studied in electrocoagulation/peanut(EC/ PS)adsorption system.The optimum conditions were: current density 2m A/cm2,initial solution p H value 7,dose of peanut shell 5g/L,initial concentration 50mg/L.The removal efficiency of MG was 98.2% under optimum conditions in 5min.And it was 22.4% higher and 18.1% higher than that in EC process and PS adsorption system,respectively.The contracting time was 55 min and 35 min shorter than that in EC process and PS adsorption system,respectively.At the optimum current density and initial concentration of MG,The effect of Solid-liquid ratio and time in modification process,initial solution p H value,and dose of Na OH-RH were studied in EC/Na OH-RH adsorption system.The optimum conditions were: Solid-liquid ratio1:8,modification time 30 min,initial solution p H value 8,dose of Na OH-RH 3g/L.The removal efficiency of MG was 97.5% under optimum conditions in 10 min,and it was 21.7% higher and 17.2% higher than that in EC process and Na OH-RH adsorption system,respectively.The contracting time was 50 min and 30 min shorter than that in EC process and PS adsorption system,respectively.The unit energy demand(UED)and the unit electrode material demand(UEMD)were calculated and discussed.The results demonstrated that the EC/bio-adsorbent adsorption coupling method achieved a reduction of 97.4%(PS)and 88.9%(Na OH-RH)UED and UEMD compared with EC process.The PS and Na OH-RH adsorption process were coinciding with Langmuir isotherm model and Freundlich isotherm model respectively.Their adsorption data fitted perfectly with the Pseudo-Second-Order kinetics.The EC system and coupling system process were also fitted perfectly with the Pseudo-Second-Order kinetics.