Preparation Of Modified Coconut Shell Carbon Material And Its Application In The Removal Of Antibiotics In Wastewater

Biomass resources are a relatively abundant resource on the earth.The activated carbon produced by biomass materials has many advantages,such as high carbon content,no pollution and many types.Therefore,the research on biomass is increasing year by year and there are many kinds of researches from wood materials to various kinds of shell materials.The emergence of antibiotics has brought great convenience to humans,but it also has adversely affected.It will eventually be enriched by the migration of the food chain,leading to the metabolism and reproduction of the organism and also making human resistance.The use of activated carbon to remove antibiotics in wastewater environment is one of commonly used methods for removing antibiotics.In this thsis,the hydrothermal and ultrasonic methods were fitted into the preparation strategy of activated carbon from the optimized coconut shell charcoal on the basis of the traditional carbonization and activation steps.And it was applied into removal of the various antibiotics.Firstly,by orthogonal analysis of hydrothermal time and temperature,the optimal reaction conditions were judged by the adsorption amount of chlortetracycline.The adsorption mechanism was initially explored by adsorption kinetics and several characterization.Secondly,the contrast tests were executed for the activated carbon which was prepared by the additive ultrasonic step,activated carbon prepared without ultrasound,and commercial carbon by assessing the adsorption effect of chlortetracycline,amoxicillin and levofloxacin.Furthermore,the mechanism of adsorption of antibiotics was proposed with the help of the adsorption kinetics and XPS.The results show that the optimal adsorption condition of coconut shell charcoal with hydrothermal step is 200 °C for 6 h,and the maximum adsorption capacity for 100 mg/L chlortetracycline is 97.31 mg/g.It accords with the models of quasi-secondary kinetics and Elovich kinetics.The adsorption process is based on chemical adsorption while the adsorption has a faster initial rate,and the adsorption rate slows down with time.After the addition of the ultrasonic step during the preparation,the adsorption activity has been increased,that is,coconut shell charcoal after ultrasonic addition > coconut shell charcoal without ultrasonics > commercial carbon.For 100 mg/L antibiotics,the dosage of activated carbon was 0.25 g/L,and the highest adsorption amounts for chlortetracycline,amoxicillin and levofloxacin were 320.99,326.22 and 397.70 mg/g,respectively.According to the analysis of adsorption mechanism,the interaction of hydrogen bonding and ?-? bond were observed between coconut shell charcoal and these three antibiotics.At the same time,it is difficult to desorb due to the very strong adsorption,and the addition of acid-base salt is less effective to desorption.It shows that the coconut shell carbon adsorbent prepared by combining ultrasonic and hydrothermal methods presents a good adsorption performance.