| Biochar is a carbon-rich solid obtained by heating biomass with little or no oxygen.It has been widely studied in the world not only for its low production cost and renewability but also for the stable physical and chemical properties with large specific surface area and excellent adsorption capacity.Biochar has been evaluated as adsorbent in wasted water treatment and the soil amendments for the serious soil degradation.In recent years,it is also used as the modifiers for the electrochemical sensors,biofuel cells,supercapacitors and so on.But the use of BC as highly conductive materials and the conductivity had been poorly studied with little information on the characteristics of electrodes and water treatment.In this study,we are focusing on the effects of pyrolysis temperature on electrical conductivity of BC.We tended to develop a biochar based sensor for rapid and sensitive determination of E2 and we also succeeded in synthesizing the magnetic biochar based on biochars with different pyrolysis temperatures using coprecipitation method,and the adsorption ability to E2 adsorption was valued.We also proposed a novel E2 remediation principle,based on the high conductivity and high adsorption properties of biochar,by magnetically ―on-off‖ control of the dual-functional magnetic biochar for adsorption and low voltage electrochemical oxidation combined method to make the magnetic biochar regenerable for continuous remediation of E2 polluted environmental water.This research would firstly study on the method of synthesizing high conductivity and high E2 adsorption efficiency magnetic biochar,and then perform E2 adsorption with magnetic biochar followed by magnetic controlled concentration of the E2 adsorbed magnetic biochar on the electrode for a low voltage electrochemical degradation.The remediation efficacy and various environmental factors effect on the remediation efficacy would also be revealed.This research would provide theoretical evidences and techniques for the adsorption and electrochemical oxidation combined continuous E2 remediation mechanism,for developing potential capability of biochar,and for the continuous remediation of E2 polluted water.(1)The biochar produced at 800℃(BCNPs)shown the highest conductivity than any other biochars with the pyrolysis temperature from 300 to 700℃.and the value of Rct for BCNPs modified electrodes was 325 Ω,which was lower than that of glassy carbon electrode(495 Ω).This electrode after being immersed in analyzed E2 solution for a adsorption saturation was used for E2 determination in phosphate buffer solution(PB,50 mM).Differential pulse voltammetry revealed that the current change was in accordance with a Langmuir adsorption model with the concentrations of E2 from 0.05 to 20 μM and a detection limit was 11.3 nM(S/N=3).Furthermore,the proposed sensor showed great accuracy and reliability,as confirmed by high-performance liquid chromatography measurements and could be successful to determine E2 in ground water samples with good recoveries.(2)we also succeeded in synthesizing the magnetic biochar based on biochars with different pyrolysis temperatures(400,600 and 800℃)using coprecipitation method,and the adsorption ability to E2 was valued.The adsorption equilibrium was reached in a short time of 25 min in 1 mg·L-1 of E2 because of the character of nano size of biochar,the exposure of micropore and good dispersion.The adsorption kinetics of E2 followed the pseudo-second-order model.The adsorption isotherms were better described by the Langmiur model with the maximum adsorption amounts of 50.24,41.71 and 34.06 mg·g-1,respectively.The prepared adsorption showed high magnetic sensitivity and could be separated under a magnetic field in 2 min.Moreover,the magnetic biochar could be regenerated by ozonation process.Therefore,the magnetic biochar are potential alternatives for the removal of E2 from water due to the ability of avoiding the problem of secondary pollution.I had fabricated the conductive magnetic biochar with two functions,as the sorbent in the solution,or as electrode materials separated on the electrode surface.It can increase the specific surface area of the electrode and reduce the distance between the target pollutant and the electrode,so as to improve the mass transfer rate and degradation efficiency of E2.In my study,we found 0.7 V could be the appropriate potential for E2 degradation.The removal efficiency of 1 mg·L-1 E2 could be reached to 92.7% after 60 h degradation.The oxidation products of E2 could be polymerized on the surface of Mag-BC800,which results in the decrease of the removal rate.In this paper,the Mag-BC800 regeneration was achieved by the solvent extraction method,so the Mag-BC800 could be reused for continuous removal of E2 in water. |
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