Jornal de Química Analítica Ambiental

Heavy metal removal is critically necessary to prevent water pollution. At various initial hexavalent chromium concentrations, adsorbent dosages, pHs, and contact periods, the removal of hexavalent chromium from aqueous solutions onto xanthated tea waste was investigated. FTIR and XRD techniques were used to characterize the adsorbent. Hexavalent chromium was initially removed from aqueous solutions with an increase in adsorbent dosage and contact time, but it was shown that the adsorption of Cr (VI) was best at a contact period of 120 min and an adsorbent dose of 100 mg/L. In a similar manner, the amount of hexavalent chromium eliminated from the aqueous solutions increased as the hexavalent chromium concentration grew and decreased as the solution's pH increased, with pH 2.0 being the ideal. Using a pseudo second-order model, the kinetics of hexavalent chromium adsorption onto modified tea trash was studied. The adsorption equilibrium data were modeled using Langmuir isotherm models. The equilibrium results for the elimination of hexavalent chromium by modified tea trash were well represented by the Langmuir isotherm model. According to the isotherm analysis, the adsorption equilibrium fit the Langmuir isotherm well. At pH 2.0, the obtained maximum adsorption capacity was around 82%. According to the findings, chromium-containing aqueous solutions can be treated using Xanthated Tea Waste as a low-cost adsorbent.

The concentrations of essential metals (Ca, Mg, Cr, Cu, Fe, Mn, Ni, and Zn) and non-essential metals (Cd and Pb) were determined in Ethiopian white rice cultivated in Fogera, Metema, and Pawe areas with their corresponding growing soils. The amounts of metals in rice and soil were determined by flame atomic absorption spectrometry, after digesting the powdered rice and soil samples with a mixture of HNO₃, HClO₄, and H₂O₂. The accuracy of the digestion procedure was assessed using the spiking method, where an acceptable percentage metal recovery was obtained in the range of 86.6%-106.7% and 87.15%-112.8% for rice and soil, respectively. The concentrations (mg/kg) of metals found in rice and soil, respectively, were in the ranges of Mg 414.28-560.89, 618.70-709.43; Fe 49.36-167.95, 11673.60-12916.67; Ca 45.21-57.71, 281.60-655.20; Mn 27.40-57.71, 168.60-416.60; Cu 12.01-61.19, 59.98-139.66; Zn 24.19-28.07, 26.59-55.85; Cr 17.65-27.45, 12.75-12.76; Ni 3.16-8.61, 2.07-11.87; Cd 1.08-1.55, 1.08-3.43 and Pb 1.08-1.55, 4.17-9.38. The pH of the studied soil farms was in the range of 5.30-5.95. Among the analyzed metals Cr showed the maximum transfer factor from soil to rice grain. Pearson correlation indicated a strong correlation for some elements between or within rice and soil samples. One way analysis of variance results indicated that for all metals in rice, the difference between means in the three sampling sites was insignificant (p>0.05), while the significant difference among soil samples was observed only for Mg, Zn, Mn, and Cd. Except for Cr, Cd, and Pb in rice and Cu and Cd in metema soil, the determined concentrations of metals were below the world health organization allowed limit.