The impact of oxalic and citric acids on the P sorption prevention and release of Fe, Cu, Zn and Mn metals In metals - calcite system.

Document Type : Original Article

Authors

1 Department of Environment and Natural Agricultural Resources,College of Agriculture and Food Sciences, King Faisal University, P.O. Box 420, Al-Hassa 31982, Saudi Arabia.

2 Soil fertility& plant nutrition Res. Dept. Soil Water and

3 Vegetable Department, Horticulture Research Institute, Agric Res. Center. Cairo, Egypt

Abstract

The efficiency of oxalic acid and of citric acid toward p sorption prevention and metal release in calcite-metals system were examined. A fixed weight of calcite was treated with fixed levels of Fe3+, Mn2+, Zn2+, and Cu2+ as chloride for 24 hrs. Then, a fixed level of P and variable rates of either oxalic or citric acid were introduced and reacted for 48 hrs.
The results obtained showed that the final supernatant EC values increased from 3.0 to 7.7 and from 3.0 to 4.7 dS m-1 due to the application from 0.1 to 15.0 mM O.C (organic carbon) l-1 as oxalic and citric acid, respectively. The final pH increased from 8.0 to 10.6 when the system was treated with oxalic acid at 0.1 and 15.0 mM O.C l-1, respectively but remained without change under the effect of citric acid. The values of Ca2+ decreased from 27 to 1.7 mg kg-1 when calcium carbonate was attacked by 0.1 and 15.0 mM O.C l-1 of oxalic acid, respectively. In the meantime, Ca2+ increased from 41 to 80 mg kg-1 when the calcium carbonate was treated with citric acid. The values of HCO3- increased from 147 to 1641 mg kg-1 under the effect of oxalic acid and from 122 to 548 mg kg-1 due to the application of citric acid. Oxalic acid prevented 60.5% of added P at 0.1 mM O.C l-1and then decreased to 14% at 0.5 mM O.C l-1. Citric acid Prevented 71% of added P at the lowest and highest rates. Both acids failed to release any of the sorbed metals.
 

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