Recovery of Cr(III) from Tannery Effluents by Diafiltration Using Chitosan Modified Membranes

Abstract

The selective recovery of chromium remaining in tannery effluents after the leather tanning process is highly desirable to potentiate its reuse, simultaneously minimizing the ecotoxicity of these effluents. To the best of our knowledge, this work evaluates for the first time the ability of a chitosan-based membrane for selective recovery of chromium from a tannery wastewater by subsequent diafiltration and selective chromium desorption, envisaging their integration after tannery wastewater treatment by reverse osmosis (RO). A polyethersulfone (PES) microfiltration membrane top-coated with a chitosan layer (cs-PES MF022) was used for selective recovery of Cr(III), from concentrate streams obtained by treatment of synthetic and real tannery effluents through reverse osmosis (RO), through a diafiltration process. The diafiltration of the RO concentrates was conducted by an intermittent addition of water acidified to pH 3.6. The prepared cs-PES MF022 membranes were able to retain 97% of the total mass of Cr(III) present in the RO concentrates, from a real tannery effluent, with a selectivity of 4.2 and 5 in reference to NH4+ and Cl−, respectively, 12.9 and 14.6 in reference to K and Na, and > 45 in reference to Mg, Ca, and S. Such a high selectivity is explained by the preferential adsorption of Cr(III) onto chitosan, and by the relatively high permeability of cs-PES MF022 membranes to the other ionic species. Proof of concept studies were performed to investigate the desorption of Cr(III) at pH 2 and 5.8. A higher Cr(III) desorption degree was obtained at pH 2, leading to a final solution enriched in Cr(III), which may be re-used in tannery operations, thus improving the process economy and reducing the hazardous impact of the effluents discharged by this industry.

Applying Chitin Enhanced Diafiltration Process (CEFP) in Removing Cobalt from Synthetic Wastewater

“…The elevated chitosan's affinity to heavy metals attracts additional attention in developing chitosan-based membranes for eliminating such metals from wastewater, benefitting from both their adsorptive and water filtration abilities. The literature review shows that Chitin is more protonated at low pH and at this pH, it is apt to retain anions through electrostatic attraction [15][16][17][18][19]. To the best of our knowledge, this is the first time in which adsorption of Co from synthetic wastewater is performed using Chitin.…”

Membranes and Integrated Membrane Operations as Clean Technologies in the Leather Industry

“…Recently, Zakmout et al [64] suggested a two-step process for the recovery of chromium (III) from tannery effluents based on a preliminary concentration of these effluents by RO, followed by treatment with a chitosan-based membrane. Real and synthetic effluents were previously concentrated by using an SW30 RO membrane (DOW Chemical Company Midland, MI, USA) which rejected more than 99% of chromium allowing for the production of a permeate stream meeting the requirements for direct discharge into natural environments.…”

Fixed-Bed Studies of Landfill Leachate Treatment Using Chitosan-Coated Carbon Composite

“…The number of bed volumes (BV) is the ratio between the volume of the adsorbate solution and the amount of adsorbent used [63]. The two parameters are commonly used to compare the ability of different adsorbents to remove a specific impurity from the influent [64].…”