Properties Of Mesoporous Activated Carbon As The Carriers Of Two Agro-antibiotics

The pesticide is an indispensable material in agricultural production. While with the environmental pollution caused by the misuse of chemical pesticides becoming more and more serious, agro-antibiotics, as the mainstay of biopesticides, draw people's attention for their low toxicity , residue and other characters which consistent with the requirement of sustainable development. However, at present, the market share of biopesticides remains low because of the shortcomings of biopesticides, such as slow efficacy, poor stability, and high prices. Therefore, the rational development of new dosage forms of agricultural antibiotics to overcome the shortcomings is an effective means to promote agro-antibiotics,Mesoporous activated carbon is one kind of adsorbents with a great surface area. Because of its well-developed pore structure and chemical stability, it is widely used in environmental protection, food manufacturing and other industries. Researchers abroad reported that as the carrier of chemical pesticides, activated carbon has the efficacy of protecting and sustained-release drugs. However, research about mesoporous activated carbon loading biopesticide has not been reported. In this paper, we carried out the research of mesoporous activated carbon as carriers for agro-antibiotics, including Avamectins and Validamycins, the following conclusions were obtained:(1) As carriers, the adsorption of mesoporous activated carbon for Avamectins and Validamycins in solution was significantly higher than other commonly used pesticide carriers. Physical characterization results indicated that the average pore size of activated carbons used in the experiment was between 2 ~ 50nm, which was in the range of mesoporous, and the mesoporous pore volume rate was more than 85%. So the activated carbons used in the study were mesoporous materials. The adsorption of Avamectins had some correlation with the surface area. Compared with the free Avamectins, the release time of Avamectins loaded by mesoporous activated carbon was extended from 90h to more than 672h, which indicated the good sustained release properties of mesoporous activated carbon. UV degradation experiments showed that, the degradation rate of free Avamectins was near 50% more than Avamectins loaded by mesoporous activated carbon after 72-hour irradiation of UV, which confirmed that the mesoporous activated carbon could protect the drugs that it adsorbed.(2) The adsorption kinetics of mesoporous activated carbon for Avamectins showed that the adsorption amount of Avamectins increased with the initial concentration of Avamectins solution and the adsorption temperature. The applicability of the kinetic models of the adsorption study done was compared by judging the correlation coefficients. It was found that the adsorption kinetics followed the pseudo-second-order model.(3)The analysis of mesoporous activated carbon surface groups before and after modification showed that the Validamycins adsorption of activated carbon modified by nitric acid increased while the Avamectins adsorption decreased. This was because the increase of hydrophilic acidic groups of the surface after the modification. However, the increase of Validamycins adsorption was not infinite for the the strong oxidation would undermine the pore structure of activated carbon when the concentration of nitric acid and the temperature increased to a certain degree, and that would weaken the adsorption capacity of mesoporous activated carbon. By contrast, the surface hydrophilicity acidic groups were reduced after modified by ammonia, and the Avamectins adsorption increased. The correlation analysis of surface acidic groups and the adsorption by SAS software confirmed that the acidic groups of mesoporous activated carbon, especially carboxyl, had a very significant correlation with adsorption.This study confirmed that as the carrier of agro-antibiotics, mesoporous activated carbon has the ability of sustained-release and UV-shielding, so it is a potential carrier of agro-antibiotics for developing new biological pesticide formulations.