Study On The Mechanism Of Functional Biochar Adsorption To Remove Typical Organic Pollutants In Water

With the development of industry and human activities,organic pollution in water is becoming more and more serious,and organic dyes and antibiotics are the most representative pollutants.Because of its simple operation,high adsorption efficiency and low operating cost,adsorption method is widely used in the treatment of organic pollutants in water,and adsorbent is the most critical factor to determine the adsorption efficiency.Compared with other traditional adsorption materials,magnetic biochar materials have a large specific surface area,are convenient for recycling,and have a good adsorption effect on organic pollutants.In this study,biochar was successfully prepared using peanut shell from agricultural waste as the main raw material,and functional biochar was prepared by magnetic modification and bimetallic modification of biochar,and it was used for the adsorption removal of typical organic pollutants（organic dyes and antibiotics）in water,and the factors affecting the adsorption removal effect of organic dyes and antibiotics were analyzed,and the relevant mechanisms were explained:（1）With peanut shell as the main substrate,pyrolysis at 500℃high temperature successfully prepared powdered biochar（BC）,Fe modification and Fe/Ni bimetal modification of BC,Fe₃O₄/BC and Fe₂Ni O₄/BC were successfully prepared;The surface morphology,microscopic characteristics,magnetic properties,specific surface area,crystal structure,composition and composition of Fe₃O₄/BC and Fe₂Ni O₄/BC were analyzed by scanning electron microscopy（SEM）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,elemental analyzer,N₂adsorption desorption,hysteresis loop analysis,thermogravimetric analysis（TG-DTG）and X-ray photoelectron spectroscopy.（2）Fe₃O₄/BC has a good adsorption removal effect on the typical organic dye malachite green in water,when the initial concentration of malachite green is 30 mg/L,the amount of magnetic biochar is 0.02 g,the p H is 11,and the temperature is 25°C,the removal rate of malachite green can reach more than 88%,Fe₃O₄/BC is repeated more than 3 times,and the removal rate of malachite green can still reach more than 75%;The adsorption process of Fe₃O₄/BC to malachite green can be described by the Langmuir model,which conforms to the quasi-secondary kinetic equation.Thermodynamic studies have shown that the adsorption process of Fe₃O₄/BC to malachite green is a spontaneous and endothermic chemical adsorption process.（3）Fe₃O₄/BC has a good adsorption removal effect on typical organic pollutants tetracycline antibiotics in water,the initial concentration of tetracycline is 20 mg/L,the dosage of Fe₃O₄/BC is 0.02 g,the p H is 7,the temperature is 25°C,and the adsorption removal rate of Fe₃O₄/BC to tetracycline can reach more than 85%;The adsorbent material is reused more than 3 times,and the removal rate can still reach more than 70%.The adsorption effect of Fe₃O₄/BC on tetracycline mainly includes pore diffusion,electrostatic effect,hydrophobic effect,π-πeffect,hydrogen bonding,etc.The study also found that Fe₃O₄/BC did not work well against typical sulfonamide antibiotics in water.（4）The specific surface area of the bimetallic modified biochar Fe₂Ni O₄/BC after loading Ni reached 222.9 m²/g,and the pore diameter and pore volume of the two were concentrated at 6.7 nm and 0.14c m²/g,5.3 nm and 0.15 cm²/g,respectively,which had good adsorption and removal effect on sulfamethoxazole,a typical sulfonamide antibiotic in water;Under the conditions of the initial concentration of SMX was 20mg/L,the dosage of Fe₂Ni O₄/BC was 0.02 g,the p H was 3,and the temperature was25°C,the removal rate of SMX could reach 80%.The adsorption mechanism of Fe₂Ni O₄/BC on SMX involves hydrogen bonding,ion exchange,complexation,andπ-πinteraction.