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 (q_e) and efficiencies of decolouration were observed for initial pH values of pH₀ = 2.00 (q_e = 246.0 mg g⁻¹) and 10.00 (q_e = 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 aim of this work was to investigate the influence of ionic strength and temperature on the adsorption of Reactive Black 5 dye on commercial powdered activated carbon. Adsorption experiments were performed at 45 °C with the addition of NaCl (c₀ = 0.01, 0.05, 0.10 and 1.00 M) and Na₂SO₄ (c₀ = 0.01 M). The results were compared with those obtained for both salts (c₀ = 0.01 M) at three additional temperatures: 25, 35 and 55 °C. For all adsorption experiments, kinetic and thermodynamic studies were performed. This research showed that the addition of NaCl, even in the concentration of only c₀ = 0.01 M, significantly enhanced dye adsorption and that higher NaCl concentration resulted in higher adsorption capacity. In addition, slightly higher adsorption was observed when Na₂SO₄ was added to the dye solution at the same concentration as NaCl, as well as at a higher temperature, regardless of the salt added to the dye solution. It was also shown that adsorption is kinetically controlled, assuming a pseudo-second-order model, and that intraparticle diffusion is not the only process that influences the adsorption rate. Finally, calculated thermodynamic parameter values for both salts (c₀ = 0.01 M) indicate that adsorption was a spontaneous endothermic process.

The continuous growth in the production, unsustainable use, and disposal of plastics in recent decades has led to the emergence of a new type of pollutant, microplastics (MPs). In this article, the focus is on the form of MPs, which are produced by the fragmentation of textile fibres during washing processes. The problems associated with the characterisation and quantification of MPs in this type of sample are related to the wide range of concentrations, forms, and degree of degradation as well as physico-chemical and biological properties. Although the basic principles for the analysis of microplastics present in the environmental samples are known, there is the lack of standardised methods for the analysis of MPs in laundry effluents and domestic washing. Therefore, the continuous development of sophisticated analytical techniques and methodologies is required for the reliable collection and isolation, quantification, and characterisation of one of the most challenging analytes. The aim of this review is to outline the key steps of MPs analysis in laundry effluents and domestic washing, focusing on those steps that are underestimated in the current literature: sampling and sample preparation for analysis. Precisely these analytical steps, which can become the main source of analytical measurement system errors, ensure the quality of the analysis. This paper emphasises the importance of monitoring background contamination and presents guidelines to ensure quality control specifically for this type of analyte.

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 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 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.