Study On The Preparation Of Marine Biochar Adsorbents And The Scavenging Activity Of Free Radicals

Free radicals have unpaired electronic groups,which can play an important role in the electron transfer of metal ions,and can also be used as reactants to participate in biological redox reactions.They play an irreplaceable role in maintaining the normal function of cells.However,excessive active free radicals attack the lipid,protein,DNA and other biological molecules in human cells and tissues,and the cells will be damaged or even die.Studies have shown that many diseases and aging phenomena are closely related to free radicals.Therefore,effective elimination of excess free radicals in the human body is the most urgent scientific problem to solve the current human aging and cancer.In this study,two marine biomasses,discarded crab shells and common kelp from the local seafood market in Zhoushan,were used as raw materials,which were pyrolyzed in the oxygen-free condition at 500℃,600℃,700℃,800℃,and 900℃through semi-carbonization technology,and then modified by KOH to prepare new marine biochar adsorbents with rich functional group structure and excellent pore structure.And the structure and performance of as-prepared materials were characterized by BET,XRD,FTIR,SEM,pore analysis,element analysis analyzer and so on.Besides,the scavenging activity of DPPH,hydroxyl free radicals,superoxide radicals using marine biochar adsorbents were analyzed.The specific research work of this paper is summarized as follows:1.From the BET data,it can be found that the specific surface area of the crab shell biochar modified by 1:2.5 KOH is up to 2046 m²/g,which is 165 times larger than that of the original crab shell;it can be clearly seen from the SEM image,modified crab shell biochar has a rich porous layered structure;it can be seen from the FTIR spectrum that a lot of oxygen-containing functional groups（-OH,-COOH,-C=O）have been added to the surface of modified crab shell biochar,which can be used as potential adsorption sites.2.Through batch adsorption experiments,the three single factors of adsorbent addition,p H,and time are discussed to influence the adsorption performance of the three radicals of·DPPH,·OH,and·O^2-,using crab shell biochar,and the scavenging properties of free radicals using crab shell biochar before and after modification were compared under the best single factor conditions.The results show that the original crab shell had no effect on the scavenging capacity of·DPPH,·OH,and·O^2-,while the modified crab shell biochar have higher scavenging capacity of·DPPH,·OH,and·O^2-,up to 98.5%,96.3%,95.8%,respectively.3.From the BET data,it can be found that the specific surface area of the kelp biochar modified by 1:3 KOH is 1302 m²/g,which is 19 times larger than the original kelp;from the SEM image,it can be seen that the modified kelp biochar has a honeycomb-like porous structure,mainly with 2-15nm mesopores.4.Through the batch adsorption experiment,the three single factors of the amount of adsorbent,p H and time affecting the adsorption performance of kelp biochar on the three radicals of·DPPH,·OH,and·O^2-were discussed,and the scavenging properties of free radicals using kelp biochar adsorbents before and after modification were compared under the best single factor conditions.The results show that the original kelp has a certain removal effect on·DPPH,·OH,and·O^2-,up to 12.3%,8.0%,6.6%,respectively,while the modified kelp biochar have higher scavenging capacity of·DPPH,·OH,and·O^2-,up to87.1%,86.4%,and 85.9%respectively.This is mainly due to the introduction of a large number of oxygen-containing functional groups（-OH,-COOH,-C=O）after modification,which could provide electrons for the three free radicals and indirectly prevent further reaction of free radicals.