Techno-Economic Analysis of Dye Separation in Textile Recycling

Abstract: This study determines the technical and economic feasibility of separating dye from a process filtrate in industrial textile recycling using electrocoagulation or sequences of membrane filtration with microfiltration, ultrafiltration, nanofiltration and reverse osmosis. The lower requirements for treating this stream, compared to previously researched dyehouse effluents, left treatments not good enough for dyehouses viable for this process filtrate. Electrocoagulation effectively removes the dye from the filtrate but limited downstream research, coagulant pollution and excessive pH control left the process filtrate unfit for recirculation to the process. Therefore, the design of this treatment method was focused on the core process and should only be applied on waste streams leaving the process. The direct operational cost of electrocoagulation was estimated to 1.22 $/m3. For membrane filtration, a complete process was designed from incoming filtrate to handling of end products. An indirect series of first external and then submerged hollowfiber- ultrafiltration shows best performance. This both concentrates pollutants and reclaims the process filtrate. A CAPEX estimation of $680 000 and OPEX of $360 000 gives a total treatment cost of 0.49 $/m3 for operations in Sundsvall, Sweden. Both electrocoagulation and membrane filtration efficiently remove dye from the filtrate and can be industrially feasible.