Chromium removal from tannery wastewaters with a strong cation exchange resin and species analysis of chromium by MINEQL+ .

Chromium (III) salts are highly applied for tanning purpose in tannery industries. The purpose of this study was removal and recovery of chromium(III) from tannery wastewater with a strong cation exchange resin. For this purpose, Amberlite 252 ZU was chosen as a strong cation exchange resin. In the first part of this study, The MINEQL+ computer program was applied depending on the optimum concentration and pH for determining Cr species in aqueous solutions. The second part of the work consists of measuring the exchange equilibrium of H+ ions and Cr(III) ions. Therefore, solutions containing fixed amounts of chromium were brought into contact with different amounts of resins. The evaluation of the obtained equilibrium parameters was done by surface complexing theory. Retention and regeneration steps were successfully performed in the column without any significant change up to 10 cycles. Efficiency was between 90 and 98% in removal studies, and between 81 and 92% in recovery studies. The results showed that a strong cation exchange resin Amberlite 252 ZU can be successfully used for chromium removal and recovery.

Biosorption of Au (III) and Cu (II) from aqueous solution by a non-living Cetraria islandica (L.) Ach.

Biosorption of Au(III) and Cu(II) from dilute aqueous solutions was investigated by biomass of the non-living Cetraria islandica (L.) Ach. The removal and recovery of gold and copper were studied by applying batch technique. The experimental parameters such as the pH of the solution, contact time, the amount of Cetraria islandica (L.) Ach. (dried lichen), the concentration of metals on retention and eluents kind and amount have been investigated. Au(III) and Cu(II) were adsorbed on the dried lichen at pH 3 and pH 8, respectively. Quantitative retention (> or = 90%) was obtained within 60 minutes for metals. Maximum capacity of 1.0 g of dried lichen for biosorption of Au(III) and Cu(II) were found as 7.4 mg of Au(III) and 19.2 mg of Cu(II). It was seen that the adsorption equilibrium data conformed well to the Langmuir model and Freundlich equation for Au(III) and only Freundlich equation for Cu(II). The method proposed in this study was applied to spiked mineral water analysis and metals adsorbed on the lichens were quantitatively (> or = 90%) recovered from mineral water samples by using 0.5 mol L(-1) HCl.

Separation of Tl(I) and Tl(III) from environmental water samples by flotation method coupled with Zeeman ETAAS determination.

An accurate, fast, and simple method for determination of thallium in environmental water samples with Zeeman electrothermal atomic absorption spectrometry (ZETAAS) by previous flotation preconcentration is given. The possibility of using cobalt(III) hexamethylenedithiocarbamate as a colloidal precipitate collector for simultaneous flotation separation of Tl(I) and Tl(III) from water matrices was studied. All experimental parameters influencing a proper flotation of both thallium ions were ascertained. The developed procedure with Co(HMDTC)3 is applied for preconcentration and separation of total thallium in water matrix before ZETAAS. The results of ZETAAS analysis are compared with those obtained by inductively coupled plasma-atomic emission spectrometry. The ZETAAS limit of detection of thallium preconcentrated by Co(HMDTC)3 is 0.031 microg/L.

A new approach to the integrated calibration in flow injection analysis.

A new proposal how to perform the analytical procedure according to the integrated calibration method is presented. An original flow injection system has been designed for this purpose. When using only a single standard solution, the measurement information gathered during a single analytical course permits construction of four calibration graphs and calculation of as many as four independent estimations of the analyte concentration in the sample examined. As the calibration method applied integrates the set of standards method and the standard addition method, the analytical estimations may be obtained in both the interpolative and the extrapolative manner and the final result can be effectively verified in terms of accuracy. The system developed was experimentally tested on the example of spectrophotometric determination of chromium. It has been proved to be capable of saving time and reagents as well as providing reliable analytical results. Owing to the instrumental simplicity and analytical efficiency the system is expected to be useful for routine analysis.

Removal and recovery of chromium and chromium speciation with MINTEQA2.

Chromium(III) is commonly found in large quantities in tannery wastewaters. For this reason, the recovery of the chromium content of these wastewaters is necessary for environmental protection and economic reasons. Removal and recovery of chromium were carried out by using ion exchange resins. To this purpose, two weakly acidic exchange resins Amberlite IRC 76 and Amberlite IRC 718 and a strongly acidic exchange resin Amberlite IR 120 were used. Basic chromium sulphate [Cr(4)(SO(4))(5)(OH)(2)] solutions in different concentrations and pH were used in all experiments as tanning baths. The resins were prepared in two different ionic forms as Na(+) and H(+). The effects of concentration, pH, stirring time and resin amount were investigated. The concentration range varied between 5 and 100 mg l(-1), pH range was between 1 and 8, stirring time between 5 and 60, and resin amount was between 50 and 1000 mg. Stirring speed was 2000 rpm during all these experiments. Exchange capacities, moisture contents and optimum conditions of these resins were determined in batch system. The results obtained showed that Amberlite IRC 76 and 718 weakly acidic resins had shown better performance than Amberlite IR 120 strongly acidic resin for removal and recovery of chromium(III) in Na(+) form. Optimum conditions were found as concentration 10 mg l(-1), pH 5, stirring time 20 min, and resin amount 250 mg. Furthermore, chromium(III) speciation was investigated for optimum concentration and pH with MINTEQA2 computer programme. The studied pH range was between 1 and 8 and concentration range was between 5 and 100 mg l(-1). Cr(OH)(2+) species were found to be dominant at pH 5 and 10 mg l(-1) concentration in batch studies. There was a correlation between experimental and computerised results.