Effect On The Removal And Toxicity Of Oxytetracycline By Biochars Derived From Pineapple Peel Waste In Soil

In this study,pineapple peel waste was chosen as the raw material to produce the three biochars(BL350,BL500 and BL650)at 350,500 and 650 ?,respectively,through the method of limited-oxygen and continuous pyrolysis.The physic-chemical properties analysis of the biochars were using a variety of characterization methods.The effects for the adsorption-desorption,degradation and seed germination of OTC in soil onto the biochars were investigated.The overarching objectives of this paper were to broaden the ways of resource utilization of agricultural waste,and reveal the mechanism of OTC removal by biochars derived from pineapple peel in soil,which provide the scientific basis for the efficient management of antibiotics pollution in soil.The main conclusions were shown as follows.(1)The pyrolysis of biochars from pineapple residue was a process of increase of the aromaticity degree,and reduction of the polarity and hydrophilicity.With the increase of pyrolysis temperatures,Ash,C%,pH,CEC,specific surface area and pore volume of the samples increased with rise in pyrolysis temperature,whereas the yield,H%,O%,Dap decreased.The biochars prepared from pineapple can be used as a kind of environmental functional material without pollution because its concentration of polycyclic aromatic hydrocarbons(16 PAHs)were within the prescribed limits by the European Union,the United States Environmental Protection Agency and the International Biochar Initiative.(2)The adsorption process of OTC on the three biochars was firstly increased rapidly,then increased slowly,and finally reached the equilibrium until 24 h.The relationship between equilibrium time and adsorption capacity was well described by the Pseudo second-order model,and the Langmuir and Temkin model can simulated the adsorption-desorption process.Adsorption of OTC onto the biochars was a process of spontaneous endothermic and entropy driven.The adsorption isotherms were nonlinear,and with the increase of pyrolysis temperature,the adsorption capacity of OTC on the biochars gradually increased,which showed as BL650>BL500>BL350.There is an obvious hysteresis effect in the desorption process,and the OTC was more difficult to be desorbed from the biochars at higher temperature.The best sorption affinity of OTC on the biochars in pH=3,followed by pH=7,while the adsorption amount was decreased gradually when pH>7.The main adsorption mechanisms of biochars for OTC might include pore filling,hydrogen bonding,electrostatic adsorption,dipole bond force and cation exchange.(3)The kinetics process of OTC in the soils amended with three biochars were also include three stages:a fast sorption step,a slow sorption step and the sorption equilibrium.Pseudo second-order model could be applied to describe the adsorption kinetics process,and the isothermal adsorption data were fitted by Freundlich,Langmuir and Temkin models.The adsorption of OTC on the biochars in soil was a complex and spontaneous endothermic process,and the sorption capacity increases with the increase of reaction(4)temperature,biochar content and carbonization temperature.The adsorption and desorption process of OTC in different soils added with biochars were not reversible,and the hysteresis effect increased with the increase of carbonization temperature and carbon content.The mechanisms of the adsorption process were primarily controlled by pore filling,electrostatic adsorption,hydrogen bonding,coordination bond,monolayer and multilayer adsorption.(5)The degradation of OTC in soil was affected by biochars.With the increase of biochar content and pyrolysis temperature,the degradation rate of OTC was accelerated,the half-life was decreased and the degradation ratio was increased.The degradation effect of OTC in soils was the best when added 1%-BL350,and the half-life of OTC was reduced from 13.03 d to 8.29 d,and the degradation rates of 14th and 60th day were increased from 38.55%and 94.86 to 84.95%and 98.84%,respectively.The variation tendency of pH value in different biocahr-soils were similar,and the pH value decreased at first day and then increased with time.The pH value of soil increased with the increase of pyrolysis temperature in the same biochar content and culture time.(5)The sensitivity for seeds shoot of cabbage and cucumber to OTC were both less than their root.The tolerance of cucumber seed to OTC was stronger than the cabbage seed.With the increase of OTC concentration,the root and shoot elongation of cabbage and cucumber seeds were promoted firstly and then inhibited.The germination of cabbage seed was promoted by the biochars in soil,and the best promotion effect of ratio(biochar to soil)is 0.1%,yet there was no significant effect on the germination rate of cucumber seed.In addition,the root and shoot elongation of cabbage and cucumber seeds were promoted,and the inhibition effect of seeds on OTC was weakened after the biochars were added to the soil,the reduction ability of inhibition rate by different ratio of biochar to soil showed in the order of 1%>0.5%>0.1%>CK.