![]() ![]() Therefore more research is needed in order to investigate micronutrient and hazardous elements associated with phosphate rock use ( Chien 2004). One of the possibilities to avoid the increase of chromium concentration in soil consists of reducing its content in phosphate ore used for the production of fertilizer. However, Cr(III) removal has attracted increasing interest in view of its oxidation to harmful Cr(VI) in the presence of oxidants in natural environments ( Lazaridis & Charalambous 2005 Tadesse et al. Compared to Cr(VI), Cr(III) has low solubility and mobility in the environment, and is usually considered as a much less dangerous pollutant ( Fandorf 1995). Chromium exists in the environment in two stable oxidation states Cr(III) and Cr(VI). The total chromium content in Algerian phosphate rock is relatively higher than that in other countries except for Moroccan phosphate rock ( Baysal et al. In general, the content of chromium in phosphate ranges between 0.3 and 460 mg/Kg ( Elvers et al. ![]() These elements can be assimilated by plants, and thus contaminate the food chain and threaten human health. The excessive application of fertilizers is the most probable source of heavy metals, contributing to their continuous accumulation in soils. Among these metals, Cr can generate serious problems and diseases (nausea, skin ulcerations and lung cancer) when it accumulates at higher levels, and as the concentration reaches 0.1 mg/g body weight it can ultimately become lethal ( Mertz 1974 Ajmal et al. Chemical elements such as Zn, Co, Cr, and Cu are necessary or beneficial to plants and living organisms at certain levels, but they can be toxic when they are present at higher concentrations in the soils ( Alloway & Ayres 1993). Phosphorus fertilizers contain varying amounts of heavy metals and other rare earth elements released from the phosphate rocks during the fertilizer manufacturing process which, from a commercial point of view, results in a decrease in the quality of the final acid product and the need for various purification processes to remove these impurities ( Mellah & Bauer 1995 Mellah & Benachour 2007). Fertilizers enhance the natural fertility of the soil or replace the chemical elements taken from the soil by harvesting, grazing, leaching or erosion ( Tekin et al. Due to the massive use of these products in agriculture, mainly with the increase in world population, demand for phosphate rocks has increased. Phosphate rocks are a vital non-renewable resource mainly used in the manufacturing of phosphoric acid and fertilizers. The results indicate that the distribution of chromium in the residual fraction is dominant. Sequential extractions proposed by the European Communities Bureau of Reference method were used to assess the distribution of chromium before and after chemical extraction. The results show that the chromium content was reduced to approximately 30% in natural phosphate using citric acid as extracting solution. ![]() The effects of some parameters were taken into consideration and optimized. To this end, the test and selection of the specific chemical reagent for efficient chromium extraction from phosphate ore were studied. The study of chromium speciation in phosphate ore allows us to evaluate its mobility and therefore its potential toxicity. The objective of this work was to select a chemical reagent capable of efficiently extracting chromium from phosphate ore in order to reduce its content. Its occurrence in industrial products at higher concentration can cause a potential risk to plants, animals and human health. Among these elements, chromium is considered as an essential micronutrient at low intake levels. However, this raw material contains various contaminants such as Pb, Cr, Cu, Ni and Zn. Phosphate rocks are a vital and non-renewable resource which is crucial for agricultural uses.
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