title: Adsorption of tetracycline onto goethite in the presence of metal cations and humic substances.
abstract: Adsorption of tetracycline, one of the most widely used antibiotics, onto goethite was studied as a function of pH, metal cations, and humic acid (HA) over a pH range 3-10. Five background electrolyte cations (Li(+), Na(+), K(+), Ca(2+), and Mg(2+)) with a concentration of 0.01 M showed little effect on the tetracycline adsorption at the studied pH range. While the divalent heavy metal cation, Cu(2+), could significantly enhance the adsorption and higher concentration of Cu(2+), stronger adsorption was found. The results indicated that different adsorption mechanisms might be involved for the two types of cations. Background electrolyte cations hardly interfere with the interaction between tetracycline and goethite surfaces because they only form weak outer-sphere surface complexes. On the contrary, Cu(2+) could enhance the adsorption via acting as a bridge ion to form goethite-Cu(2+)-tetracycline surface complex because Cu(2+) could form strong and specific inner-sphere surface complexes. HA showed different effect on the tetracycline sorption under different pH condition. The presence of HA increased tetracycline sorption dramatically under acidic condition. Results indicated that heavy metal cations and soil organic matters have great effects on the tetracycline mobility in the soil environment and eventually affect its exposure concentration and toxicity to organisms.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, PR China. yanping-zhao@163.com
authors.forename: Yanping
authors.initials: Y
authors.lastname: Zhao
authors.forename: Jinju
authors.initials: J
authors.lastname: Geng
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Wang
authors.forename: Xueyuan
authors.initials: X
authors.lastname: Gu
authors.forename: Shixiang
authors.initials: S
authors.lastname: Gao
mesh_terms: D000327:Adsorption; D000900:Anti-Bacterial Agents / Q000302:isolation & purification*; D002412:Cations / Q000737:chemistry; D006812:Humic Substances / Q000032:analysis*; D058085:Iron Compounds / Q000737:chemistry*; D008670:Metals / Q000737:chemistry; D008903:Minerals / Q000737:chemistry*; D012989:Soil Pollutants / Q000302:isolation & purification*; D013752:Tetracycline / Q000302:isolation & purification*
chemical_list: D000900:Anti-Bacterial Agents; D002412:Cations; D006812:Humic Substances; D058085:Iron Compounds; D008670:Metals; D008903:Minerals; D012989:Soil Pollutants; C094886:goethite; D013752:Tetracycline