Toward Resource Recovery from Textile Wastewater: Dye Extraction, Water and Base/Acid Regeneration Using a Hybrid NF-BMED Process

Abstract

In this work, textile wastewater is explored for resource recovery in a hybrid loose nanofiltration (NF)-bipolar membrane electrodialysis (BMED) process for fractionation of dyes and salt, in view of dye purification and water and salt reuse. A loose nanofiltration membrane, i.e., Sepro NF 6 (Ultura), found to have a low salt rejection (0.27% in 120 g· L −1 NaCl solution) and high rejection for direct dyes and reactive dyes (≥99.93%), was used for fractionation of dye/salt mixtures through diafiltration. In diafiltration, the addition of pure water with a volume factor of 5.0 can effectively remove the NaCl salt by using Sepro NF 6 with an invariable dye concentration, in view of the recovery of high purity dyes. The overall salt rejections in diafiltration for the dye/salt mixtures with 40, 50 and 60 g·L −1 NaCl are 2.2%, 1.8% and 1.1%, respectively, enabling a further treatment by BMED. Subsequently, application of BMED for reuse of salt-containing NF permeate demonstrates that desalinated water with ∼100 ppm of NaCl can be obtained, and base/acid can be produced from the salts without any membrane fouling by dyes. Therefore, the hybrid loose NF-BMED process allows for resource (i.e., dye, salt and pure water) extraction from textile wastewater, which closes the salt and water cycle, in view of process intensification.

Biocatalytic Self-Cleaning Polymer Membranes

“…In general, the permeation flux of the membrane was recorded after every single step to be able to identify exactly the reason for performance changes (fouling, less fouling, and self-cleaning). To simulate a long-time application, a high starting protein concentration was used, and fouling cycles were repeated several times as also reported by others [40][41][42][43][44]. First, the initial pure water permeation flux of a membrane disc sample (Φ = 45 mm) was determined ( Polymers 2015, 7 by the speed of the sample transporter.…”

“…and was interpreted according brane was recorded after every changes (fouling, less fouling, protein concentration was used, s [40][41][42][43][44]. First, the initial pure rmined (♦ symbol) by dead-end n solution (■ symbol) containing 7.0.…”

“…A backwashing step with 120 mL of pure water (˝symbol) was conducted after every 1.6 L of protein fouling step simulating real water treatment conditions. Finally, pure water permeation flux ( and fouling cycles were repeated several times as also reported by others [40][41][42][43][44]…”

“…However, to simulate a long time fouling in real systems it is necessary to repeat several fouling cycles (using high protein concentrations) which is also described by many others in the literature [40][41][42][43][44]. The method by which we performed the test aimed for proving that the self-cleaning effect is originated by the enzyme activity, and not by back-washing steps or surface modification effects.…”

Emulsion Liquid Membrane for Cadmium Removal: Determination of Liquid Membrane Components

“…Some research in textile wastewater treatments have been done by coagulation, adsorption, membrane separation and extraction. [6][7][8][9][10][11][12][13][14] Those conventional technologies have their own advantages and disadvantages. Emulsion liquid membrane (ELM) as an alternative of solvent extraction provides advantages of combining extraction and stripping process in a single step, thus minimising the equipment as well as processing time.…”