Absorption Characteristics And Mechanisms Of Sulfonamides In Aquatic Solutions By Biochars Derived From Different Biomass Materials

Sulfonamides is a class of artificial synthesis of broad-spectrum antibacterial agents, commonly used in medicine, animal husbandry and aquaculture, which is widely existed in various environmental media. Residues of sulfonamides are transferred and accumulated by biological chain, in addition to adverse effects on the ecological environment, it will also lead to bacterial resistance, and even harmful to human health. Biochar is a widely source of raw materials of new environmental functional material, which has abundant micropore structure and large specific surface area, can be used as high performance adsorbents, and has a strong adsorption capacity for organic pollutants.In this paper, the choice of peanut shell, pennisetum hybrid and maize straw three kinds of agricultural waste used for prepared biochar, respectively with sulfadiazine and sulfachlorpyridazine as the research object, invesitigated different biomass materials and influence factors of the adsorption characteristics of sulfonamides, and investigated the adsorption mechanism by adsorption thermodynamics and kinetics, structural characterization and elemental analysis etc, provide a theoretical basis for the treatment of antibiotic wastewater by biochar. The main results were as follows:(1)Different raw materials have different carbonization yield, different biochar adsorption of sulfonamides showed different characteristics, the carbonization yield and adsorption effects are manifested as maize straw biochar>pennisetum hybrid biochar>peanut shell biochar. Adsorption of sulfonamides by the same biochar also showed different characteristics, Sulfachlorpyridazine removal effect were better than that of Sulfadiazine.(2)The removal ratio of sulfonamides were affected by biochar addition amount, adsorption time, initial concentration of sulfonamides and p H value of the solution, but the removal effect of sulfonamides by temperature and ionic strength were negligible. Considering various influence factors on the removal efficiency of sulfonamides, the best conditions for removal of sulfadiazine are controlling the temperature at 25±1?, keeping the initial p H, using a sorbent dose of 8g/L for sulfadiazine and 5g/L for sulfachlorpyridazine of maize straw biochar as adsorbent, controlling the initial concentration of sulfonamides in 10mg/L, and making the reaction time in 4 hours. The sulfadiazine and sulfachlorpyridazine removal rate can reach 95.64% and 98.32%, respectively.(3)The results of adsorption thermodynamics studies and adsorption kinetics studies indicated that: at the experimental temperature of 283 K, 298 K and 313 K, the adsorption isotherms process of three kinds of biochar on sulfonamides can be accurately described by the Freundlich isotherm equation with the correlation coefficient above R2=0.948, and the adsorption kinetics were followed the pseudo second-order equation. The adsorption process is mainly Dominated by chemical adsorption.(4)The results of scanning electron microscope(SEM)for three kinds of biochars showed that: there were Significant difference among surface structure of different biochars, and the peanut shell biochar's surface is smooth, no obvious micropore structure, and pore structure and quantity of pennisetum hybrid biochar and maize straw biochar's surface more abundant. The XRD analysis showed that: The pennisetum hybrid biochar and maize straw biochar have low ash content and high activation performance, their structure are made up of several layers of aromatic ring folded graphite-like crystals microcrystalline material, which directly caused them have more micropores and adsorption properties higher than the peanut shell biochar. The elements analysis results showed that: three kinds of biochar have higher C content, and have high polarity, aromaticity, reducibility and stability, while their different O content, ash content,polarity, reducibility and stability of biochars caused the difference of adsorption efficiency for sulfonamides. The infrared spectroscopy analysis showed that: the surfaces of biochars containing hydroxyl, carboxyl, ester and other functional groups, and the O-H bond of carboxyl and phenolic hydroxyl, and the C-O bond of hydroxyl, ester and ether, obviously the difference of the two functional groups mainly caused the difference of adsorption properties of three kinds of biochar. The Boehm titration analysis to quantify the content of each functional group and their surface acidic functional group contents as follows: maize straw biochar>pennisetum hybrid biochar>peanut shell biochar, which further indicates that the content of acidic functional groups of differences is the main cause of biochars adsorption performance of different, so the maize straw biochar adsorption performance of sulfonamides was best, the second is pennisetum hybrid biochar, peanut shell biochar was worst.