Zinc Chloride Recovery from Textile Recycling Wastewater Using a Multi-stage Membrane Filtration Process

Abstract

Textile waste presents significant harm to the environment, prompting the development of advanced textile recycling technologies.

One such process recycles cellulosic fibers using zinc chloride (ZnCl2) at certain hydration levels to dissolve the cellulose, which is later precipitated by the addition of water and can be re-spun into new fibers. However, this process uses large amounts of zinc chloride and generates substantial volumes of zinc chloride wastewater due to the repeated cellulose washing steps.

Zinc chloride is both corrosive and hazardous to aquatic life, and its recovery is critical for environmental protection and resource conservation. One possible method for recovery is membrane filtration.

This study evaluated the use of a multi-stage membrane filtration process for the recovery of zinc chloride from textile recycling wastewater. The process involved sequential filtration using a 10-um mesh to remove larger particles, ultrafiltration (UF) for cellulose removal, and nanofiltration (NF) or reverse osmosis (RO) for zinc chloride concentration. The membranes were evaluated based on particle size distributions, flux, and zinc chloride concentrations. Pure water fluxes for the NF/RO membranes were also measured to assess fouling and cleaning efficiency.

Membrane screening for the UF stage found the ETNA10PP membrane to be optimal, yielding in the permeate with the lowest particle size as determined by dynamic light scattering measure-ments as well as a relatively high flux (1683 L/m2h).
In the subsequent NF/RO stage, all tested membranes exhibited larger particles in the permeates than in the feed, suggesting membrane degradation. The RO98 membrane achieved the highest concentration of zinc chloride (8.28%). However, because it exhibited signs of membrane degradation as well as a significantly lower flux (14 L/m2h), it is not suited for zinc chloride recovery.

Overall, the multi-stage membrane filtration was found to be ineffective for concentrating zinc chloride. Instead, concentration of the ultrafiltration permeate using an evaporator is recommended.

Popular Abstract

Textile waste presents significant harm to the environment, prompting the development of advanced textile recycling technologies.

One promising method dissolves cellulose, found in cotton fibers, using zinc chloride (ZnCl2). The cellulose is then turned back into a usable material for making new clothes. However, this process uses large amounts of zinc chloride and generates substantial volumes of zinc chloride wastewater.

Zinc chloride is both corrosive and hazardous to aquatic life. Recovering and reusing it would improve the recycling process to be safer and more sustainable.

One possible method for recovery is membrane filtration. Membranes are barriers which allow some substances pass through while retaining others. Membrane filtration produces permeate (the liquid that has been filtered through the membrane) and concentrate (the liquid that did not pass through the membrane).

In this study, a multi-stage membrane filtration process was tested to recover zinc chloride from textile wastewater. First, a mesh was used to remove larger particles, followed by a finer filtration called ultrafiltration (UF) to separate cellulose, and then an even finer filtration, nanofiltration (NF), and alternatively the finest filtration, reverse osmosis (RO), to concentrate zinc chloride. The membranes were evaluated based on the size of the particles they filtered, the concentration of zinc chloride, and their wastewater filtration capacity.

Membrane fouling, where the pores for filtration become clogged and dirty, affects how well membranes can perform. Cleaning the membrane reduces the impact of fouling. To assess foul-ing and cleaning efficiency, pure water was pushed through the membrane and measured before filtration, after filtration, and after cleaning.

In the UF stage, the ETNA10PP was found to remove most of the larger particles and allowed the wastewater to pass through quickly.

However, in the NF/RO stage, the tested membranes showed signs of damage because larger particles were found in the permeates and the concentrates. The RO98 membrane achieved the highest concentration of zinc chloride (8.28%). Despite this, because it exhibited damage and took a much longer time to filter the wastewater, it is not suitable for zinc chloride recovery.

• author: Capinpuyan, Caitlin Rose
• supervisor: Mikael Sjölin; Mahla Bagherigelvardi
• organization: Chemical Engineering (M.Sc.Eng.)
• course: METM01 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: membrane, membrane filtration, zinc chloride, textile recycling, resource recovery, membrane engineering, membrane technology, ultrafiltration, nanofiltration, reverse osmosis, cellulose, cotton
• language: English
• additional info: This master thesis project has been conducted as part of the Erasmus Mundus Joint Master Degree in Master in Membrane Engineering for Sustainable Development, MESD, funded by the European Union.; This project was done in collaboration with ShareTex AB.
• id: 9205449
• date added to LUP: 2025-06-25 13:11:41
• date last changed: 2025-06-25 13:11:41