Grafting And Loading Modification Of Biochar And Its Adsorption Removal Properties For Arsenic And Cadmium

Arsenic(As)and cadmium(Cd)pollution in soil and water are serious in China.Biochar has become more and more attention owing to its excellent heavy metal adsorption capacity.In this study,biochar was prepared from the corncob and modified by 7 kinds of grafting and loading.The sorption experiments showed that cyanogen grafting-modification biochar(MBC350)was the high-efficiency adsorption for Cd2+ and loaded TiO2 biochar(BCTD)was the best effect on H2AsO4-and Cd2+.To systematically elucidate the removal mechanism of Cd and As on biochar,the influence of preparation conditions and environmental factors on removal of Cd2+ and H2AsO4-by biochar was studied in soil and water.Firstly,the optimal preparation conditions,i.e.4.5 g/g NaOH,14 g/g urea and 1.6 mL/g acrylonitrile,were gained for MBC350.BET and FTIR confirmed that modification enhanced the surface area and pore volume of biochar and the-CN group was only grafted in the lignin of MBC350 successfully.The XPS showed that the removal of Cd2+was due to the formation of N-Cd groups and the Na+ion exchange between Cd2+and MB350.The co-existing ion of Ca2+?Pb2+?H2AsO4-inhibited the MBC350 adsorption capacity,and the effect of K+,Cl-and NO3-were all within 6%.The pseudo-second-order kinetic and Freundlich isotherm model could better describe the sorption of Cd2+on MBC350.The adsorption capacity of Cd2+on MBC350 was 85.65 mg/g.Secondly,the optimal preparation conditions of BCTD were hydrothermal ultrasound BC550 for 15 minutes,titanium butyl concentration 5 mL/g,reaction time 1 h,sealed dry temperature 100?.The results can prove that ultrasonically reacting enhanced the surface area and pore volume of biochar,and loading TiO2 on the surface and inner pores of biochar improved chemisorption complexation and ion exchange.The Langmuir maximum adsorption capacity of BCTD to Cd2+and H2AsO4-was 72.62 mg/g and 118.06 mg/g.The removal process of Cd2+ and H2AsO4-was a spontaneous,endothermic and irreversible.The initial Cd2+and H2AsO4-concentration was less than 100 mg/L,which have synergistic adsorption on BCTD,if not,they have the competitive adsorption effect.The results of soil remediation for cadmium and arsenic showed that the remediation efficiency of cadmium and arsenic in cinnamon soil was increased by 100%and 72.03%respectively,that of in yellow soil was increased by 54.05%and 27.37%.BCTD increased the contents of TN,aK and Tom in the yellow soil,promoted the heavy metals deactivation and improved the richness and activity of microorganisms.In cinnamon soil,BCTD increased soil pH,promoted heavy metals deactivation and increased the microorganism growth with carbohydrate and carboxylic acids as carbon sources.PCA and BCR in both soils indicated that the smaller C/O rate of corncob-based biochars was favorable to As stabilization in soil.The SA and TV of biochar were negatively correlated with the leaching concentration of Cd.This work will provide a reference for biochar technology in the recycling and reutilize of agricultural waste,and provide technical support in the treatment of wastewater containing heavy metals and the soil remediation.Especially,the deactivation and treatment of arsenic and cadmium have an important guiding significance.