Preparation Of Iron Phosphide/Bamboo-Based Phosphorus-Doped Biochar And Its Adsorption Performance Toward La(Ⅲ)

Transition metal phosphide porous carbon composites have excellent electrical conductivity,chemical stability,high specific capacitance,high photothermal conversion efficiency,and cycle stability,and are highly promising for development and application prospects in the fields of energy storage,catalysis,and biomedicine.The preparation of multipurpose transition metal phosphide porous carbon composites using biomass resources with abundant reserves and natural structures and highly biocompatible reagents is in line with the strategic needs of sustainable development,and is an important way to solve resource and environmental problems.Based on this,this paper adopts an in-situ one-step pyrolysis synthesis strategy to construct iron phosphide/bamboo-based phosphorus-doped biochar（FeP/PBC）using bamboo chips as the carbon source,phytic acid as the phosphorus source and iron chloride as the iron source to investigate its performance as a conventional adsorbent and capacitive deionization electrode for the removal of rare earth element La（Ⅲ）,and the microscopic morphology,pore structure characteristics,crystal structure,chemical element composition,chemical bonding state and electrochemical performance of FeP/PBC were characterized to reveal their adsorption mechanism,which is excepted to providing theoretical support for the green and safe preparation and high value-added utilization of transition metal phosphide carbon matrix composites.The main research contents are as follows:（1）Using bamboo as raw materials,phytic acid as phosphorus source,and ferric chloride as iron source,FeP/PBC was prepared by in-situ one-step pyrolysis.The results showed that phytic acid can be used as a pore forming agent and a doping modifier to achieve the activation and phosphorus doping of bamboo based biochar substrates.At the same time,phytic acid can chelate with Fe³⁺,and then be converted into FeP during high-temperature pyrolysis.The activation temperature and phytic acid ratio showed a positive correlation with the specific surface area,total pore volume,and iodine adsorption value of FeP/PBC.Under the optimum processing conditions,when the heat treatment temperature is 800℃,and the mass ratio of bamboo chips,phytic acid,and iron chloride is 1:3:0.02,the specific surface area of FeP/PBC is 909 m² g^-1,and the microporous and mesoporous pore volumes are 0.374 cm³ g^-1and 0.175 cm³ g^-1,respectively.The electrochemical analysis results showed that the specific capacitance of FeP/BC-800 can be as high as 160 F g^-1 at a current density of 1A g^-1.（2）FeP/PBC was used as adsorbent for the conventional adsorption of rare earth element La（Ⅲ）.The results showed that with the increase of heat treatment temperature and the proportion of phytic acid,the adsorption capacity of FeP/PBC-800 for La（Ⅲ）increased first and then decreased.Under the condition of heat treatment temperature of 800℃,the mass ratio of bamboo chips,phytic acid,and iron chloride was 1:3:0.02,the adsorption capacity of FeP/PBC-800 was as high as64.82 mg g^-1,which was 45.8%and 26%higher than bamboo based biochar and phosphorus doped bamboo based biochar,respectively.FeP/PBC introduced FeP active adsorption site,which were chemisorbed with La（Ⅲ）in the solution to form La-O-Fe.At the same time,FeP/BC-800 exhibits good adsorption selectivity,with adsorption selectivity of FeP/PBC reached 82.07%and 61.71%in La（Ⅲ）/Na（I）and La（Ⅲ）/Ca（II）systems,respectively.（3）FeP/PBC was used as electrode materials for the electrosorption of rare earth element La（Ⅲ）.The results showed that the electric adsorption capacity of FeP/BC-800 at a working voltage of 1.2V was 91.92 mg g^-1,which was 62.51%,54.46%,and 24.67%higher than that of iron doped bamboo based biochar,bamboo based biochar,and phosphorus doped bamboo based biochar,respectively.At the same time,FeP/PBC-800 exhibits excellent adsorption selectivity,which reached 92.25%and 87.64%in La（Ⅲ）/Na（I）and La（Ⅲ）/Ca（II）systems,respectively.After five adsorption-desorption cycles,the adsorption capacity and retention rate of FeP/PBC-800 were 45.35 mg g^-1 and49.33%,respectively.The combination of FeP and phosphorus-doped bamboo based biochar enhances the adsorption of the double electric layer and introduces the Faraday adsorption site FeP.Driven by electric field,La（Ⅲ）enters the pores of FeP/PBC-800 through the electrostatic force to form a double electric layer and undergoes surface adsorption and intercalation and redox reactions with the electrode.