The aim of this work was to investigate the influence of initial pH value (pH0) on the isothermal adsorption of Reactive Black 5 (RB5) dye on commercial powdered activated carbon. Four initial pH values were chosen for this experiment: pH0 = 2.00, 4.00, 8.00, and 10.00. In order to investigate the mechanism of adsorption kinetic, studies have been performed using pseudo-first-order and pseudo-second-order kinetic models as well as an intraparticle diffusion model. In addition, thermodynamic parameters of adsorption were determined for pH0 = 4.00. Results of this research showed that the initial pH value significantly influences the adsorption of RB5 dye onto activated carbon. The highest adsorption capacities (qe) and efficiencies of decolouration were observed for initial pH values of pH0 = 2.00 (qe = 246.0 mg g−1) and 10.00 (qe = 239.1 mg g−1) due to strong electrostatic interactions and attractive π···π interactions, respectively. It was also shown that the adsorption of RB5 dye on activated carbon at all initial pH values is kinetically controlled, assuming a pseudo-second-order model, and that intraparticle diffusion is not the only process that influences on the adsorption rate.
The dominant type of polymer particles in water, sediment, and various organisms partly derives from natural and synthetic fibres released in the washing process. Pollution of aquatic recipients with these particles poses an interdisciplinary problem throughout the world. Wastewater from washing represents a dispersion system with different particle sizes that is also loaded with the source of the particles. Due to this complex system, the qualification and quantification of this type of pollution is difficult. In this paper, the laser diffraction technique was applied to characterize particles in effluents from washing and rinsing materials made of a mixture of cotton and polyester. The results obtained through the analysis prove that the laser diffraction technique is acceptable for the characterization of a composite effluent sample. The advanced statistical technique of multivariate analysis confirmed the interrelationship of the parameters of this complex dispersion system.
The influence of 3, 10 and 50 washing cycles on the properties of cotton fabric and cotton-polyester blend in plain weave, was investigated in this study. In addition to the analysis of tensile properties in weft and warp directions and thickness, the number of particles produced in the dry state was also measured after 3, 10 and 50 washes. After washing, the entire effluent was analysed by determining the total suspended solids (TSS), the total solids (TS), the pH value and the conductivity. To determine the similarity of the observed wash cycles and properties of all processed samples, hierarchical cluster analysis (HCA) was performed. The fabric changes indicated by total wear in the warp direction after 50 washing cycles compared to unwashed ones amounting to 41.2% for cotton and 30.9% for cotton-polyester blend, may be attributed to the synergy of washing factors and raw material composition. Cotton fabric produced significantly more particles than cotton-polyester fabric in the dry state after the examined washing cycles in all size categories. A smaller number of released particles are in the larger size category >25 μm. The obtained TSS values confirm the degree of loading of the effluent with particulate matter from the analysed fabrics, since the detergent consists of water-soluble components. The HCA dendrograms confirmed that the release of particles during the first washing cycles is mainly determined by the structural properties of fabrics, while in the subsequent cycles the synergistic effect of chemical, mechanical and thermal effects in the interaction with the material prevailed.
The influence of iron ions at concentrations of 0.2, 0.5, and 1.0 g/L on optical brighteners of the groups stilbene and biphenyl in solution and on cotton fabric was investigated. Both groups of optical brighteners are intended for detergent formulations. The influence of iron ions was studied by absorption and fluorescence spectra in solution and by whiteness degree, identifying color differences using CIEL*a*b* coordinates and Ultraviolet Protection Factor (UPF) of cotton fabrics. The obtained results in solutions and cotton fabrics showed different behavior of optical brighteners stilbene and biphenyl in the presence of iron. Stilbene compounds with metal ions produced new species capable of absorbing in the UV-B region of the spectrum. A biphenyl compound in combination with iron had no effect on the absorption properties. Both optical brighteners were influenced by iron ions in the sense of fluorescence quenching. The influence of iron ions in single- and two-bath treatments of cotton fabrics after one cycle on whiteness degree and UPF was negligible.
Research on the sources of microplastics (MP) in the environment and the parameters that lead to the loss of microfibers from synthetic textiles during washing have recently attracted public attention. Considering the involvement of a variety of structural and process parameters, it is important to choose methods for quantifying fibers as MP pollutants that migrated during the washing process. In the research to date, various sampling techniques and analytical protocols for the identification of polymers from washed synthetic textiles have been applied. In the present research, pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS), was applied to verify the composition of the filter residue isolated from washing and rinsing effluents. A comparison with bases of polymeric materials has proven the presence of potential environmental pollutants in the form of microfibers released during the washing process. The investigation confirmed that fragments of cotton cellulose residues predominate in relation to polyester. Based on the list of identified compounds generated by Py-GC/MS results and their retention times the multivariate data analysis proved the influence in the bath composition.
Textile materials from polyester fibres are sensitive to washing, especially at higher temperatures, due to their thermoplastic properties, hydrophobic nature and sensitivity to the alkaline medium. The issue of microplastic fibres’ (MFs’) release from polyester textiles is a topic that attracts the attention of researchers from different scientific fields, since microplastics are now among the serious environmental risks. In this study, two washing protocols, a standard and an innovative procedure, were presented, aiming to preserve the properties of polyester fabrics and reduce the pollution of washing effluents. The standard procedure followed HRN EN ISO 6330, while the innovative procedure was a modification of the standard that involved gradually cooling the bath before rinsing. The effects of these washing protocols were studied based on the physicochemical properties of the fabrics compared to the unwashed material, the composition of the effluents, and the filtrates after 10 cycles. The characterisation parameters of the fabrics, effluents and filtrates according to the standard and the innovative washing protocols showed differences in the observed parameters during the 10 washing cycles. The obtained results show the usefulness of the proposed concept of cooling the bath before rinsing in order to preserve the properties of polyester fabrics and reduce the load of washing effluents. Hierarchical cluster analysis (HCA) also confirmed differences in pH, conductivity and turbidity for effluents and filtrates from standard and innovative washing protocols.
In this research, the modification of different polyester structures (fabrics and knits) by the biopolymer chitosan was studied to evaluate the effects of the polyester structure and treatments on the particulate pollution of wastewater. The pristine polyester and the chitosan-polyester fabric and polyester knit composites were washed cyclically with standard ECE A detergent at 60 °C. The laser diffraction technique was used to characterize the particle size of the washing wastewaters from the 1–5, 6–10 and 1–10 wash cycles. In addition, the total solids (TS), total suspended solids (TSS), total dissolved solids (TDS), turbidity and chemical oxygen demand (COD) were also determined, according to standard procedures. The obtained results show the influence of the polyester fabrics and polyester knit structures and chitosan-polyester composites on the particle size distribution (PSD) in the washing wastewater. Differences in the values of the characteristic parameters, especially the span value and shape factor (k) of the individual curves, are visible, indicating the release of particles during the washing process. The experimental results show that the laser diffraction technique is suitable for characterizing the particle dimensions of the washing wastewater for different pristine polyester structures and chitosan-polyester composites. Modification with chitosan has been shown to provide potential protection against the release of microplastic particles into the environment.
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