Interaction of Tetracycline with Aluminum and Iron Hydrous Oxides

Abstract

The effect of solution chemistry (pH, sorbate-to-sorbent ratio, ionic strength (/)) and reaction time on the sorption of tetracycline to the hydrous oxides of Al (HAO) and Fe (HFO) was examined. Sorption to HAO increased with increasing pH upto pH 7 (no such trend for HFO) above which it decreased at higher pH values for both the hydrous oxides. Experimental results indicate that ligand-promoted dissolution is occurring during tetracycline sorption to these hydrous oxides. Ligand-promoted dissolution was more significantfor HAO than HFO attributable to the difference in labile surface sites between these two sorbents. The ability of tetracycline to form strong complexes with Al and Fe will increase the solubility of these minerals. Sorption of tetracycline was quite rapid and equilibrium was achieved after 8 h. However, soluble metal (Me: Al or Fe) concentrations attained equilibrium only after 24 h. Ligand-promoted dissolution appears to be a two-step process; initially, 1:1 Me-tetracycline soluble complexes are formed and as the reaction progresses 2:1 complexes existed. Increasing / (from 0.01 to 0.5 M) decreased the sorption extent only at higher sorbate-to-sorbent ratios suggesting the dominance of inner-sphere type complexes at low equilibrium tetracycline concentrations. Spectroscopic evidence indicates that tricarbonylamide and carbonyl functional groups of tetracycline could be responsible for sorption to mineral surfaces. Our research findings will increase understanding of the environmental occurrence, fate, and transport characteristics of antibiotics, which are considered as emerging organic contaminants.

Uptake of oxytetracycline and its phytotoxicity to alfalfa (Medicago sativa L.)

“…7). Thus, soil solution pH is an important factor influencing the bioavailability of OTC in soil (Kulshrestha et al, 2004;Gu, 2005;Jones et al, 2005) and the transport from soil to plant. Time-dependent uptake of OTC by alfalfa showed that there was an equilibrium status of OTC uptake after 4 h (Fig.…”

“…For example, in Denmark, concentrations of oxytetracycline ranging from 2.5 to 50 mg g À1 in soil and from 33 to 2000 mg g À1 in pig manure have been reported (Loke et al, 2002). The fate of antibiotics, including sorption and fixation, mobility and transport in soil, has been well documented (Tolls, 2001;Kulshrestha et al, 2004;Gu, 2005;Jones et al, 2005), whereas knowledge of their toxicity to plants and their uptake and transport into plants is poorly understood (Boxall et al, 2003;Thiele-Bruhn, 2003). The accumulation may or not affect the growth and development of plants; however, the uptake into plants may represent an important exposure pathway of these compounds to humans and other biota.…”

Coadsorption of Ciprofloxacin and Cu(II) on Montmorillonite and Kaolinite as Affected by Solution pH

“…Current understanding of Cip and tetracycline sorption to soils and soil minerals has revealed similarities in the mechanisms, with both compound classes being sorbed onto aluminosilicate clays either via cation exchange and cation bridging (3,(8)(9)(10) or via surface complexation (4,5,11,12). However, the exact mechanism of surface complexation is unknown.…”

Facile synthesis, characterization of a MnFe2O4/activated carbon magnetic composite and its effectiveness in tetracycline removal

“…As a result, the adsorption capacity of the composite did not change significantly with the decrease in surface area. In addition, complex formation of TC with metal and metal oxide present on the surface of the activated carbon might also contribute to their higher adsorption since compounds with carboxylic and phenolic functional groups are capable of forming complexes with metals [14].…”