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Effects of copper (Cu) and aluminum (Al) on the adsorption of sulfathiazole (STZ) and tylosin (T) to peat and soil were investigated using a batch equilibration method. Results show that Cu suppressed STZ adsorption onto peat and soil at pH 5.0 because of the electrostatic competition, while increased STZ adsorption at pH 5.0 due to the formation of STZ-Cu complexes and/or Cu bridge. In contrast, Al only decreased STZ adsorption at pH 6.0, and exerted slight effect on STZ adsorption at6.0. As for T, both Cu and Al suppressed its adsorption over the entire pH range owing to three reasons: 1) electrostatic competition between Cu/Al and T(+); 2) Cu/Al adsorption made the soil and peat surface less negatively charged, which was unfavorable for T(+) adsorption; 3) the shrunken pore size of peat and soil retarded the diffusion of large-sized T into these pores.

The effect of lead on the sorption of 2,4,6-trichlorophenol (2,4,6-TCP) on soil and peat was investigated using a batch equilibration method. Lead markedly diminished the sorption of 2,4,6-TCP, and 2,4,6-TCP had little effect on lead sorption. Peat was a more effective adsorbent for 2,4,6-TCP than soil. The desorption hysteresis of 2,4,6-TCP verified the presence of high-energy sorption sites. Mechanisms of lead suppression effect on the 2,4,6-TCP sorption included the following: Firstly, lead accelerated the aggregation of colloids, the aggregates covered the surface in part and shrunk the pore sizes of the adsorbents, hence decreased the sorption of 2,4,6-TCP. Secondly, X-ray absorption and Fourier transform infrared spectroscopy study suggested that lead competed with 2,4,6-TCP for carboxylic, phenolic and Si-OH groups of organic matter and clay minerals. Such competition was partly responsible for the overall suppression effect of lead on the sorption of 2,4,6-TCP.

The effect of copper on adsorption of p-nitrophenol on two typical Chinese soils was investigated using a batch-equilibration method. Adsorption experiments were carried out when both copper and p-nitrophenol were adsorbed Simultaneously, and when copper was previously adsorbed oil soils. It was observed that adsorption of p-nitrophenol decreased with increasing copper concentrations thereby indicating a competition between copper and p-nitrophenol for occupying the adsorption sites oil soils. Moisture increased the hydrated sphere and the acidity of Water Surrounding the cation, which further reduced the adsorption of p-nitrophenol. Fourier transform infrared Spectroscopy study provided the direct evidence for the coordination of p-nitrophenol sorbed by soils with metal cation in n-hexane system. It was observed that the perturbations included a red shift of the v(sym) (NO) hand, a concomitant blue-shift of the v(sym) (NO) hand and a blue-shift of C-N hand when compared with the infrared spectra obtained from water solution. (c) 2005 Elsevier Ltd. All rights reserved.