Study On Removal Of Different Electrical Organic Pollutants By Adsorption Of Biochar Modified By Reducing Agent

The operation cost is high when using advanced oxidation process(AOPs)for treatment of organic wastewater.Incomplete oxidation of organic pollutants leads to highly toxic organic intermediates,such as 1,4-benzoquinone,benzoquinone,catechol,hydroquinone,etc.In this paper,the adsorption of 1,4-benzoquinone,methylene blue,acid orange II and PVA in aqueous solution by wheat-straw biochar was studied.Methylene blue is cationic dye with positive charge,acid orange II is anionic dye with negative charge,1,4-benzoquinone shows weak electricity,polyvinyl alcohol(PVA)is a kind of high molecular polymer with no charge.Because of the limited surface functional groups and low adsorption capacity of organic pollutants,the wheat-straw biochar modified by reducing agent(Na2SO3 and FeSO4)was prepared under the condition of limited oxygen.The soaking time was 2h,the concentration of reductant was 0.001 mol/L,and the pyrolysis temperature was 600?.SEM images showed that the Na2SO3 modification greatly increased the porosity of wheat-straw biochar.The FeSO4 modification formed smaller and more various fragments of wheat-straw biochar,which increased the specific surface area of biochar and improved the adsorption performance.FTIR showed that the carbonyl group was increased on the surface of FeSO4-modified biochar,and that the surface of wheat-straw biochar contains more phenolic hydroxyl groups,which is beneficial to the removal of organic pollutants.Boehm analysis showed that the content of phenolic hydroxyl group on the surface of Na2SO3-modified and FeSO4-modified biochar was significantly higher than that of unmodified-biochar,and that among the three kinds of biochar,FeSO4-modified biochar has the most weak acid group and carboxyl group.The effects of pH value and adsorbent dosage on the adsorption performance were investigated,which showed that the removal rate of the adsorbate is gradually increased with the increase of adsorbent dosage,and that because the functional groups of several kinds of biochars and the electrical properties of organic pollutants are different,the p H has different effects on the adsorption process.Thermodynamic results showed that the adsorption of the four kinds of organicpollutants is a spontaneous and exothermic reaction.The kinetic results showed that compared with the linear pseudo-first-order modle,the linear pseudo-second-order model is more suitable to describe the adsorption of organic pollutants,which indicated that the chemical adsorption of organic pollutants may be the limited step.Wheat-straw biochar can be regenerated by 0.5mol/L NaOH.The wheat-straw biochar has high adsorption capacity and high stability of adsorption and desorption.The removal rate of three successive cycles is also very high.