We studied the sorption reactions of zinc (Zn) with freshly prepared hydrous iron oxide gels modified to provide phosphorus/iron (P/Fe) ratios of 0, 0.05, 0.10, 0.20, and 0.40. Hydrous oxides have a high adsorptive capacity for Zn in acid soils and soils affected by submergence. Zinc concentrations from 0 to 10 mg/L were used to evaluate sorption phenomena where P and Zn interact to affect Zn solution concentration. Sorbed P tends to lower the ZPC of the oxides and increases the net negative charge on its surfaces. The pH of the media affects solution Zn-P-Fe relationships, because the surface charge on the oxide is pH-dependent. This study concludes that hydrous iron oxides may play an important role in the sorption of Zn in soils and possibly affect its availability to crops.
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