Waste hemp and flax fibers, and cotton and cotton/polyester yarns, available in large quantities from the textile industry, were used as cheap and effective sorbents for the removal of methylene blue from wastewater. Waste fibers and yarns were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, iodine sorption, water retention, and point of zero charge, as well as through the determination of crystallinity index and degree of surface crystallinity. The adsorption of methylene blue was optimized by examining the influence of contact time, initial concentration, temperature, and pH value. It was found that the more ordered structure of cotton and cotton/polyester yarns leads to lower adsorption capacities and better agreement with pseudo-second order kinetic and Langmuir isotherm model, while the more heterogeneous structure of flax and hemp fibers shows higher capacities for methylene blue adsorption, better described by the pseudo-first order kinetic and Freundlich isotherm model. Based on the obtained results, waste lignocellulosic fibers and yarns can be used for the discoloration of wastewater, thereby solving the problem of waste generated in the textile industry.

As new technologies are developed, the demand for rare earth elements (REEs) has increased, despite limited awareness of their significant impact on people and the environment. In this study, waste fly ash was used as a precursor to synthesize inorganic aluminosilicate polymers by adding an activator to the alumina and silica compounds of the ash. Due to their structure and adsorption potential, their application for the removal of selected REEs (Gd³⁺, Y³⁺, and Sc³⁺) from water has been investigated. A decrease in the intensity of the quartz peak at 2θ of 26.6° in the XRD spectrum and the disappearance of the albite and mullite peaks due to dissolution during alkaline activation in both modified samples were observed. The appearance of a peaks at 2θ of 29.3° and 39.3° corresponding to calcite in the modified sample indicates the presence of wood ash. A shifting of the band in the DRIFT spectrum to 1030 cm⁻¹ on the spectra of modified samples corresponds to the vibrations of Al-O and Si-O bonds and the formation of a polymeric network structure (Si-O-Si or Si-O-Al). According to pH_PZC values, thermodynamic and kinetic parameters, and chemical composition, the presumed mechanism of REE adsorption is chemisorption and ion exchange. The highest adsorption efficiencies (up to 95%) for all examined REEs in both single and mixed REE solutions were obtained from an alkali-activated mixture of fly ash and wood ash. The results of this research are significant for expanding knowledge about the removal of REEs from the environment, the reduction of waste ash by their modification, and their potential subsequent use in construction as additives.

In this study, the possibility of using modified potato starch, with nitrogen-containing chemical agents (melamine, cysteine and histidine) as green adsorbents for removing pharmaceuticals and pesticides from water has been investigated. The influence of additional modification of amino-starch with clay and diatomaceous earth was examined. The effect of the applied modification on the structural, surface and morphological properties was determined by FTIR, XRD and SEM analysis, while the adsorption properties were determined through the effectiveness of prepared materials to remove selected pollutants from spiked and real water samples. The efficiency of investigated amino?starches for the adsorption of pharmaceuticals and pesticides decreases in order: starch?histidine > starch?cysteine > starch?melamine, with a slightly better efficiency for pharmaceuticals adsorption. Additional modification of amino?starches with clay/diatomaceous earth did not contribute to the increase in adsorption efficiency. It was found that the influence of the matrix of real water samples on the adsorption efficiency is up to 10%, which represents a promising potential for applying amino?starch as a cheap and effective adsorbent for wastewater treatment. Also, starch?histidine and starch?cysteine showed the possibility of reusing up to three cycles of adsorption.

In this study, we report on the method of preparation, and application of modified potato starch following the principles of sustainable development. Modified starch was tested as an adsorbent for removing heavy metals and dyes from water. The modification method is environmentally friendly, without the use of expensive and toxic chemicals, and economically profitable with low operating costs. The starch modification is based on introducing amino functional groups into the starch structure, followed by the addition of montmorillonite clay, in order to obtain a novel bicomposite, and to investigate the influence of clay on the adsorption properties. It has been found that applied treatments induced the changes in morphological and surface characteristics of the obtained adsorbents consequently increasing the adsorption efficiency of modified samples for the removal of both, heavy metal ions and dyes.