The Properties And Mechanisms Of FeO_x And MoS₂-Modified Biochar Composite Materials For Heavy Metal（loid）s Removal From Water

Inorganic pollutants or toxic metal ions such as arsenic,cadmium and other pollutions are of special concern since these are persistent and accumulate in nature and has serious threat to human health.Among them,arsenic and cadmium pollution in water is particularly serious.Water is not only necessary for the maintenance of life activities,but also necessary to maintain industrial and agricultural production.Man-made pollution and natural events cause pollutants to enter the water environment and endanger the health of water bodies.Therefore,it is particularly important to improve the quality of the environment,especially the quality of water bodies.The adsorption method is one of the effective methods to reduce/eliminate heavy metals in the water environment,and the adsorption agent is the key factor to determine the efficiency of heavy metal adsorption.Carbon materials have better removal efficiency to pollutants,but there are also defects such as low adsorption capacity and poor combination strength.Iron oxides and two-dimensional sulfides have great potential for charge transfer,the surface has reactive oxygen/sulfur bonds,and excellent affinity for metal ions.In order to improve the adsorption performance of carbon materials.This study creatively loads magnetic iron oxides and molybdenum disulfide to the biochar surface,with a view to increasing the number of biochar surface adsorption active sites,improving the adsorption performance of the material,and explains its adsorption mechanism by using X-ray photoelectron spectroscopy,X-ray diffraction,Fourier transform infrared spectroscopy and scanning electron microscope.The following results have been achieved:（1）Magnetic biochar（MBC）was prepared as adsorbent material.The results revealed that the pore structure of the material was smaller,the surface area was greater,the number of surface oxygen-containing officer groups increased.The MBC800-0.6₃₀₀00 demonstrated good results for Cd（Ⅱ）removal from aqueous solution around 46.9 mg g^-1.The adsorption of Cd（Ⅱ）by MBC800-0.6₃₀₀ was pH dependent.After sorption,the used MBC800-0.6₃₀₀ in the aqueous solution could be collected with ease by the application of an external magnetic force.（2）The MoS₂-impregnated biochar（MoS₂@BC）was prepared by hydrothermal method.The Langmuir isotherm and pseudo-second-order kinetics model better defined the sorption of Cd（Ⅱ）on MoS₂@BC.The MoS₂@BC exhibited an excellent adsorption capacity 129 mg g^-1 for Cd（Ⅱ）on Langmuir basis,7.33 times more than the maximum adsorption value of pristine biochar.The adsorption mechanism included ion exchange,electrostatic interaction,Cd（Ⅱ）-πinteractions,and complexation with surface functional groups.Among them,the dominant mechanism involved Cd-O（38.3%）bonds and Cd-S complexation（61.7%）on MoS₂@BC.（3）The molybdenum disulfide impregnated iron-biochar was prepared.The molybdenum disulfide impregnated iron-biochar material demonstrated good arsenic and cadmium adsorption capacity,and could be collected from the system with ease by the application of an external magnetic force after use.Iron oxide and molybdenum dioxide on the surface of biochar had a synergistic effect improving the efficiency of arsenic and cadmium removal.The maximum arsenic adsorption capacity of the MSF@BC800 was 28.4 mg g^-1 and the maximum cadmium adsorption capacity of MBC@MoS₂ was139 mg g^-1.The adsorption mechanism of arsenic followed the inner–sphere complexes,As（ⅡI）to As（V）oxidation,electrostatic interactions,multilayer coverage,and chemisorption.The adsorption mechanism of cadmium included the electrostatic attraction,Cd-S complexation,ion exchange,and Cd-πinteraction.