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The remediation of heavy metals requires the development of efficient adsorbents. Macroporous polystyrene divinyl benzene based resins are known for their excellent surface characteristics for the effective adsorption of metals. In this paper, we propose an effective adsorption procedure for chromium (VI) using aliphatic primary amine as a guest in Amberlite XAD-4 polymeric sorbent as the host. The adsorption of chromium was quantitative at pH 2.5. The adsorption process was in accordance with pseudo second order kinetics and the maximum adsorption capacity was found to be 75.93 mg g−1 with good adherence to Langmuir isotherm model. The free energy change ΔG0 increased with temperature and the negative ΔH0 and ΔS0 values indicate the exothermic nature of adsorption and decreased randomness at the adsorbent-solution interface. In aqueous medium, the water molecules surround the hydrophobic host polymeric matrix and this cage effect is responsible for the reduction in entropy of the system. The regeneration of the adsorbent was effective in alkaline medium and the efficacy of the adsorbent was tested for the removal of chromium from tannery waste water. [ABSTRACT FROM PUBLISHER]

A simple extractive separation method has been developed for the determination of chromium based on the extraction of Cr (VI) as its ion-pair with tribenzylamine (TBA). The ion-pair is extracted at acidic pH using toluene as the diluent. The concentration of chromium in the organic phase was measured spectrophotometrically at 309nm. The influence of experimental variables such as pH, sample volume, equilibration time, diverse ions etc. has been studied in detail. The extracted chromium (VI) could be stripped to the aqueous phase using NaOH as the stripping agent. The extracts were characterized using FT-IR spectroscopy. A detection limit of 0.08μgmL−1 could be achieved and the validity of the method was checked in real tannery effluent, electroplating waste water and spiked water samples. [Copyright &y& Elsevier]

The universal concern for heavy metal removal demands effective methods for detoxification. Chromium(VI) is one such heavy metal which is recognized to be carcinogenic. In this paper, an efficient approach is proposed for the removal of chromium based on the impregnation of trioctylamine (TOA) on a macroporous Amberlite XAD-1180 polymeric matrix. Chromium(VI) could be quantitatively adsorbed in an acidic medium (pH 2 to 3), while chromium(III) could be retained on the resin matrix at alkaline pH. The adsorbent was characterized using Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) studies. The comprehensively characterized adsorbent showed a high adsorption capacity of 171.82 mg·g−1in accordance with the Langmuir isotherm model. The adsorption follows second-order kinetics, and a study of the various thermodynamic parameters such as Gibbs energy, entropy, and the enthalpy changes showed that the adsorption decreases with an increase in temperature. Column studies and regeneration data validated the performance efficiency of the adsorbent with large sample volume tolerance (1 L) and high preconcentration factor (100). The resin column could be regenerated using NaOH after the removal of total chromium without any loss in the performance efficiency for nearly 15 cycles. Chromium could be effectively separated from a synthetic mixture of various ions, thus making it a viable proposition for the detoxification of chromium from industrial effluents. [ABSTRACT FROM AUTHOR]