Biochar Adsorption of Antibiotics and its Implications to Remediation of Contaminated Soil

Abstract

Antibiotic contamination in water and soil has been widely investigated. However, there is still no effective removal method for antibiotics from water or soil environments. Therefore, the single and competitive sorption dynamics of ionizable tetracycline (TC), sulfamethazine (SMZ), norfloxacin (NOR), erythromycin (ERY), and chloramphenicol (CAP) adsorbed by NaOH-activated and hematite-modified biochars were investigated. NaOH-activated biochar (NAB) showed much better antibiotic sorption than the hematite-modified biochar (HMB). The affinity coefficient of NAB for TC, NOR, and ERY were at least 100 times higher than that of the HMB. The sorption rate of the five target antibiotics was faster in the single-solute systems than in the ternary-solute systems. Sorption capacity was inhibited in the competitive system for all five antibiotics adsorbed by either the NaOH-activated or hematite-modified biochars. Antibiotic sorption by the biochars was governed by electrostatic interactions, π-π electron donor-acceptor (EDA) interactions, and hydrogen bonding. All five antibiotics showed similar adsorption trends in pH treatments of both biochars. However, the sorption capacity slightly increased from pH 7 to pH 9 in HMB compared with those in NAB, as the metal ions from the hematite modification provided cation bridging combinations to negatively charged antibiotics at a high pH value. These observations are useful for producing NaOH-activated biochar as an engineered sorbent to reduce the bioavailability of antibiotics in water and soil. The results are important for the application of biochars to use as soil amendments in the remediation of antibiotic co-pollution in agricultural water or soils.