Removal of disperse dye from alcoholysis products of waste PET fabrics by nitric acid-modified activated carbon as an adsorbent: Kinetic and thermodynamic studies

Abstract

Decolorization technology is a critical problem of high-quality chemical recycling and recovery of waste poly(ethylene terephthalate) (PET) textiles. In order to deal with this problem, nitric acid-modified activated carbon (AC-HNO3) was utilized as an adsorbent for removal of C.I. Disperse Red 60 (DR60) from the glycolysis products of waste PET fabrics. The glycolysis product was bis(2-hydroxyethyl) terephthalate (BHET). The pore structure and surface properties of AC and AC-HNO3 samples were characterized by N2 adsorption, differential thermogravimetric analysis (DTG) and elemental analyses (EA). Modification with nitric acid increased the amount of oxygen groups of the activated carbon from 12.3% to 18.0% and enhanced the electrostatic attraction between dye molecules and activated carbon. The average color removal ratio of DR60 on AC-HNO3 increased into 97.6 ± 0.5%, which is better than that on raw AC (85.0 ± 1.6%). Relative whiteness of BHET increased from 40.3 ± 0.9% to 98.3 ± 1.1%. The adsorption kinetics for DR60 on the AC-HNO3 were studied using pseudo-first order and pseudo-second order models and fitted to the latter well ( R2 = 0.9999). To investigate the adsorption equilibrium behavior, Freundlich and Langmuir models were examined. The results showed that the Langmuir model provided better correlation ( qmax = 163.9 mg/g). The adsorption isotherms at different temperatures were used for the determination of thermodynamic parameters. Based on the data of Δ G0 , Δ H0 and Ea, the adsorption process was physisorption.

Ion-Exchange Resins for Efficient Removal of Colorants in Bis(hydroxyethyl) Terephthalate

“…Li et al used modified activated carbon to remove the color of BHET, and the decoloration rate was 97%. However, the retention efficiency of BHET was not mentioned . In this study, the loss ratio of BHET was investigated for the first time.…”

“…However, the retention efficiency of BHET was not mentioned. 17 In this study, the loss ratio of BHET was investigated for the first time. All these resins caused BHET loss in a more or less amount.…”

“…Moreover, when compared with other decolorization methods, decolorization method using the D201 resin not only can show an excellent decoloring performance but also can achieve a good quality in r-PET (Table S2). ,, Thus, the decoloration method of BHET by the D201 resin was feasible.…”

“…In this regard, various measures have been attempted for the decoloration of BHET, including recrystallization, distillation, oxidation, and active carbon adsorption. − Among these methods, the recrystallization process is quite simple, but the solvent separation is difficult; the additives from the polymer still exist and BHET loss is large. The oxidation method can achieve significant decoloration efficiency, whereas it also causes secondary pollution and even result in the destruction of BHET’s molecular structure.…”

Carbon footprint and water footprint assessment of virgin and recycled polyester textiles

“…Through the physical or chemical recycling process, the recycled polyester has a wide range of potential applications similar to virgin polyester, serving as the raw material of textiles. 11 Are the recycled polyester textiles more environmentally friendly than virgin polyester textiles? There are some researchers focusing on the comparison of the environmental impacts caused by the production of virgin polyester materials and recycled polyester materials.…”