In this study, dispersive liquid-liquid microextraction method was used for the preconcentration and simultaneous determination of Co(II) and Fe(III) in water samples as their oxinate chelates. In dispersive liquid-liquid microextraction process, methanol and chloroform were used as disperser and extracting solvents, respectively, and the ligand 8-hydroxy quinoline was used as a chelating agent for the extraction of Co(II) and Fe(III). HPLC was applied for the quantitation of the analytes after preconcentration. An experimental design, central composite design, coupled with response surface methodology was used for the optimization of the involved experimental parameters. In addition, the effect of various experimental parameters in the extraction was investigated using one variable at a time method. The calibration graphs were linear in the range of 20-4000 mg/L with the LODs of 3 mg/L for both analytes. The RSDs for six replicate measurements of 500 mg/L of Co 21 and Fe 31 were 3.3 and 4.1%, respectively.
In this study a new method for the simultaneous determination of Cu(II) and Zn(II) ions in water samples was developed by dispersive liquid-liquid microextraction preconcentration followed by HPLC with UV detection. An experimental design, central composite design, coupled with response-surface methodology was used for the optimization of the involved experimental parameters. In the proposed approach, 8-hydroxy quinoline (HOX) was used as a chelating agent and chloroform and methanol were chosen as the best extraction and dispersive solvents, respectively. Some factors influencing the extraction efficiency of copper and zinc ions and their subsequent determinations, including extraction and dispersive solvents kinds and volumes, pH of sample solution, concentration of the chelating agent, salting out effect and reaction time were studied and optimized. Under the optimum conditions, the calibration graphs were linear in the range of 10-4000 mg/L with the detection limits of 3 mg/L and the quantification limits of 10 mg/L for both analytes. The RSD for six replicate measurements of 500 mg/L of Cu 2þ and Zn 2þ were 2.9% and 5.7%, respectively.
In this two‐part report, the efficiency of rice bran in removal of heavy metals such as cadmium, lead, zinc, nickel, copper and iron(III) from aqueous solution is investigated. The different experimental conditions such as pH, temperature, volume of solution, bran amount, particle size, exchange time, stirring speed, etc. are studied, and the optimum conditions are selected in part 1 of this series of reports. The efficiency of bran in removal of heavy metals is presented with and without treatments. For treatment, heat or acid, alkali and salt solutions were used. The results obtained show that after treating with saturated sodium chloride solution, its efficiency for Ni2+ and Zn2+ improves. At pH 5, all studied cations have recoveries more than 93% (lead and cadmium 100%). The exchange speed is very high and has preference over the classical ion exchangers.
In part 2 of this report related parameters of the rice bran (as a sorbent of heavy metals) such as exchange capacity, distribution coefficients and isotherms, etc. were studied. The obtained results show that selectivity of the bran towards heavy metals such as Cu(II), Cd(II), Fe(III), Ni(II), Zn(II) and Pb(II) is very high. Also, distribution coefficients between aqueous solution and bran are more than 10 4 so that all cations are completely adsorbed by the bran in relatively low concentrations. The principal advantages of this sorbent are as follows: high efficiency, very high exchanging speed, cheapness (in comparison with conventional resins), performance in batch and continuous conditions and producing no environmental pollution. The only disadvantage of the bran is low exchanging capacity for some elements (but for lead it is comparable to classical resins); however, it is able to eliminate heavy metals in mg/L level and above. On the other hand, due to low cost of bran and high cost of recovery of ion exchangers there is no necessity to recover the bran. Reproducibility of the proposed method in removal of heavy metals is excellent and the relative standard deviations for eight repeated removals for all cations with the exception of iron are less than 1%.
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