Application of porous styrene resin loaded carboxymethyl cellulose-stabilized nano-zero-valent iron for highly efficient hexavalent chromium removal

In order to improve the reactivity of nZVI for Cr(VI) removal, porous styrene resin loaded carboxymethyl cellulose-stabilized nano-zero-valent iron (CMC-D201@nZVI) was firstly prepared by the simple liquid phase reduction method....

Chromium removal from tannery effluents by adsorption process via activated carbon chat stems (Catha edulis) using response surface methodology

Objective In tannery processing, water consumption is high, which generates wastewater as a by-product and numerous pollutants such as chromium heavy metals that make adverse effects of water bodies and the surrounding environment. This study analyzed, chromium (VI) removal from wastewater through activated carbon chat stem was investigated. Adsorption is a common treatment method via activated carbon due to its cost-effective, profitable, and removal efficiency of these heavy metals. Results The proximate analysis of moisture content of chat stem has 6%, activated carbon ash content of 17.35%, volatile materials of 20.12%, and fixed carbon contents of 56.53%, which are well-matched the standards quality of activated carbon. As the process parameter varies, the increment of the chromium removal efficiency was from 62.5 to 97.03%. The maximum adsorption efficiency was observed at 30 g/L dosage of the adsorbent, at pH 4, and contact time at 180 min of activated carbon from chat stem waste was found 97.03%. FTIR was used to characterize the surface of the chat stem before and after adsorption. Langmuir and Freundlich are used for short contact time’s adsorption isotherm 0.9839 and 0.9995 respectively, which conformed, no visible change in the corrosion state.

Sherry wine industry by-product as potential biosorbent for the removal of Cr(VI) from aqueous medium

A low-cost biosorbent obtained from the Palomino Fino grape seed, a Sherry wine industry by-product, has been proposed as a way of valorising this material. The biomass was characterised obtaining values of 0.68 ± 0.05 g mL−1 for bulk density, 1.02 ± 0.09 g mL−1 for apparent density and 33.3% for porosity. The pHpzc was 5.2 and the surface negative charge value was 2.4 ± 0.2 mmol g−1. The analysis of surface morphology showed differences due to the sorption. The results showed a promising potential for chromium(VI) removal from aqueous solutions. The studies were carried out in batch scale and a 23 factorial design was applied for the optimisation of the process. A percentage of 91.7 ± 0.6% was achieved for the biosorption of Cr(VI) under optimal conditions using pH 5.5, 15 g/L of biosorbent and 8 h of contact time. The biosorption capacity showed a remarkable linearity from 0 to 2 mmol L−1 Cr(VI) and a precision of 0.64% for the removal of 1 mmol L−1 of metal. Langmuir, Freundlich and Temkin isotherm equations and the parameters of six kinetic models were used in the equilibrium modelling and identifying the mechanism of the biosorption. The combination of physical and chemical sorption mechanisms was proposed for the chromium removal with a high maximum sorption capacity (qmax = 208.3 mg g−1). Thermodynamic parameters indicated the spontaneous and endothermic nature of the chromium removal. The successful biosorption was based on the special grape seed components with a relevant content in antioxidant and lignocellulosic compounds.