Abstract
Biochars produced from the pyrolysis of waste biomass under limited oxygen conditions could serve as adsorbents in environmental remediation processes. Biochar samples derived from rice straw that were pyrolyzed at 300 (R300), 500 (R500) and 700°C (R700) were used as adsorbents to remove tetracycline from an aqueous solution. Both the Langmuir and Freundlich models fitted the adsorption data well (R2 > 0.919). The adsorption capacity increased with pyrolysis temperature. The R500 and R700 samples exhibited relative high removal efficiencies across a range of initial tetracycline concentrations (0.5mg/L-32mg/L) with the maximum (92.8%–96.7%) found for adsorption on R700 at 35°C. The relatively high surface area of the R700 sample and π–π electron-donor acceptor contributed to the high adsorption capacities. A thermodynamic analysis indicated that the tetracycline adsorption process was spontaneous and endothermic. The pH of solution was also found to influence the adsorption processes; the maximum adsorption capacity occurred at a pH of 5.5. These experimental results highlight that biochar derived from rice straw is a promising candidate for low-cost removal of tetracycline from water.
Highlights
Antibiotics are widely used to control infectious diseases and as animal feed additives to promote healthy growth
The results suggest that biochar derived from rice straw appears to be a useful means of treating tetracycline-contaminated water
This study showed the biochars pyrolyzed at 500 and 700 ̊C were relatively high efficient at removing tetracycline from an aqueous solution
Summary
Antibiotics are widely used to control infectious diseases and as animal feed additives to promote healthy growth. In China in 2013, annual antibiotics consumption was approximately 162,000 tons, with 52% of the total attributed to animal use [1]. Such levels of consumption notably increase the environmental concentration of antibiotics. This is because animals only adsorb a portion of the dosage given to them and a large volume of antibiotics is excreted via urine and feces [2]. Tetracycline is one of the most extensively used antibiotics and is often used in the livestock industry where wastewater analysis has shown tetracycline concentrations reaching tens of micrograms per liter [1, 6]
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