Chemical Modification Of Biochar And Its Adsorption Toward Copper (Ⅱ)

Biochar has wide application in environmental remediation and pollutant removal because of its special structural properties. Much more attention has been paid to biochar modification for improved heavy metal wastewater treatment. The basic physicochemical properties of biochar, development of conventional preparation technologies, advances in chemical modification and its application in environmental pollutant treatment were introduced in this dissertation briefly. We prepared amino functional groups modified biochar, and used it to remove Copper(II) from wastewater. The adsorption kinetics and thermodynamics were evaluated in order to understand the sorption process. In addition, the effects of environmental impact factors, such as pH, humic acid, and ionic strength, were also systematically studied in this dissertation, and adsorption mechanism was proposed finally. Several main conclusions of this research are as follows:1. Amino modified biochar was prepared by nitration substitution and reduction reactions using sawdust char as initial raw material. Althrough there was no obvious difference in specific surface area and surface topography compared with unmodified biochar, significant changes appeared in elementary composition and surface functional groups. The nitrogen percentage increased from0.3%to4.6%, and a large number of amino functional groups were newly formed on the biochar surface after amino modification.2. The adsorption capacity of modified biochar is nearly five-fold of the pristine biochar. Heavy metal Cu(Ⅱ) sorption kinetics conformed to a pseudo-second-order reaction very well, which highlighted the chemisorption rate-controlling mechanism. On the other hand, sorption thermodynamics conformed to Langmuir model with perfect fitness, suggesting that copper sorption on amino modified biochar is monolayer coverage.3. There was negligible effect on Cu(Ⅱ) sorption on amino modified biochar when pH ranged from4.0-6.0, while ionic strength and competitive cations had an significant effect on Cu(Ⅱ) sorption. The adsorption capacity of modified biochar decreased when ionic strength increased. The fixed bed column adsorption method suggested the effective treatment volume for the modified biochar is eight times higher than that of the pristine biochar, 4. The Cu(Ⅱ) combined with the amino functional groups through strong chemical complexation based on the comparison of XPS and ATR-FTIR analysis before and after adsorption.