Preparation,Physicochemical Properties Of Humic Acid/Chitosan/Silica Aerogel Composite Adsorbent And Its Application In The Adsorption Of Deltamethrin

With the increasing application of pyrethroid pesticides in agricultural cultivation,the possibility of people being poisoned by pesticides is increasing.In recent years,adsorption technology shows high efficiency in purifying water contaminated with pesticides.SA（Nano-silica aerogel,SA）has great advantages in adsorption due to its large specific surface area,multi mesoporous and macroporous properties,while SA has certain limitations in adsorbing organic pollutants due to the lack of active groups.Although HA（Humic acid,HA）contains a large number of carboxyl and other adsorption active groups,it cannot be used as an adsorbent alone due to its high solubility in water.Although the combination of HA and SA can exert their respective advantages,their binding ability is poor.The combination of CS（Chitosan,CS）and HA changes the hydrophobicity of CS and increases the fixation rate of HA.The physical combination of CS and SA changes the hydrophobicity of SA.In this paper,a green composite adsorbent was synthesized for the adsorption of pesticides in water and the removal of pyrethroid pesticides in vegetable juice,in order to explore and broaden the application of this composite adsorbent in the removal of pyrethroid pesticides in food.The main research conclusions are as follows:（1）A HA-CS-SA composite adsorbent was prepared using HA,CS,and SA as raw materials,and its structure was characterized.The complexation of NH₃⁺and COO^-between CS and HA increases the retention rate of HA,reduces the crystallinity of CS,and improves its hydrophobicity.The specific surface area of HA-CS-SA is 483.243m³/g,and its pores are mainly 2 nm micro mesopores.HA-CS-SA is a high-quality green composite adsorbent that combines large specific surface area and porosity,as well as rich adsorption active groups such as carboxylic acid,amino group,and hydroxyl group.（2）It investigated the characteristics of composite adsorbents for adsorbing DM（Deltamethrin,DM）by studying the effects of pH,temperature,adsorption time,composition of adsorbent raw materials,dosage of adsorbent,and initial concentration of DM on the adsorption efficiency of DM.It was shown that there was a significant impact on the adsorption of DM of different pH,and the optimal pH is 4;It has the best adsorption effect on DM of HA-CS-SA;It was increased of the adsorption capacity and removal rate of within the extension of adsorption time and gradually reach equilibrium,and there was promoting effect of adsorption of increasing the temperature.the optimum conditions of temperature,adsorption dosage and DM initial concentration is30℃,4 mg and 25 mg/L which the adsorption capacity and removal rate of the composite adsorbent for DM were 151.17±4.15 mg/g and 75.59±2.08%,respectively.（3）Equilibrium studies were done with different temperature,and it was found that the studied followed the Langmuir non-linear isotherm models（R²>0.993）.The dates of adsorption capacity of experimental and fitting in 30℃were 126.15 mg/g and128.48 mg/g,respectively.Kinetic studies were done with different adsorbent dosage and temperature,and the data were assimilated with pseudo-first order,pseudo-second order and intra-particle diffusion kinetic equations,and it was found that the studied followed the pseudo-second order kinetic equation（R²>0.995）.The dates of adsorption capacity of experimental and fitting in 30℃were 126.15 mg/g and 128.48 mg/g,and the date at 4 mg were 151.17 mg/g和159.72 mg/g.Thermodynamic analysis was also down,and it was found that the process of adsorption was more spontaneous at higher temperature.It was reduced to 92.41±0.61%of the removal efficiency After 5 cycles.It was mainly through hydrogen bonding and pore adsorption that the combination between DM and SA,and it was mainly through electrostatic action between DM,CS and HA.（4）It was studied that removed the DM with the compound adsorbent from apple juice and carrot juice.The maximum adsorption capacity was 136.99±0.15 mg/g and137.97±0.94 mg/g,respectively.The maximum removal rates were 83.15±0.20%and83.73±0.17%,respectively.There was no significant effect on pH,soluble solids content,total acid and color difference of apple juice and carrot juice.Therefore,there was a good application prospect in removal of DM by complex adsorbents.