PFAS, or per- and poly-fluoroalkyl substances, are a broad group of man-made organic compounds that are very persistent, mobile, and tend to bioaccumulate. Their removal from different environmental media is becoming increasingly important because they are associated with a multitude of (eco)toxicological effects on both humans and the environment. PFAS are detected in wastewater, groundwater, drinking water, and surface water, with the subcategories of PFOS and PFOA being the most detected. These organic compounds are divided into polymeric and non-polymeric groups. Non-polymeric PFAS are of great research interest due to their frequent detection in the environment. Numerous methods have been applied for the removal of PFAS and are divided into destructive and non-destructive (separation) techniques. Given the strength of the C–F bond, the destruction of PFAS is challenging, while for most of the separation techniques, the management of isolated PFAS requires further consideration. Most of the techniques have been applied to small-scale applications and show some limitations for larger applications, even though they are promising. Adsorption is an environmentally sustainable, economical, and high-performance technique that is applied to remove several classes of emerging pollutants from water. In this review, the use of various types of adsorbents for PFAS removal from water is reported, as well as the expected adsorption mechanisms. There are several technologies being considered and developed to manage PFAS; however, they are still in the experimental stage, with each showing its appeal for potential larger applications.

In this study, a new composite adsorbent consisting of aluminum-modified activated carbon (abbreviated hereafter AC@Al) was synthesized for the removal of the Ibuprofen compound (IBU), a non-steroidal anti-inflammatory drug (NSAID). Coconut shells were used as a source material for activated carbon, which was then modified with AlCl₃ to improve its properties. Adsorbent dosage, pH and initial IBU concentration, as well as contact time and temperature, are some of the factors affecting adsorption that were investigated in this work. Specifically, at pH 2.0 ± 0.1 with the application of 0.5 g/L of AC@Al in 100 mg/L of IBU, more than 90% was removed, reaching 100% with the addition of 1.0 g/L of the adsorbent. The IBU kinetic data followed the pseudo-second-order kinetic model. Non-linear Langmuir, Freundlich, Sips and Redlich–Peterson isotherm models were used to interpret the adsorption. According to the correlation coefficient (R²), the Langmuir model was found to best match the experimental data. The maximum adsorption capacity (Q_max) according to the Langmuir model was found to be as high as 2053 mg/g. The positive values of ΔH⁰ (42.92 kJ/mol) confirmed the endothermic nature of the adsorption. Due to the increasing values of ΔG⁰ with temperature, the adsorption of IBU onto AC@Al proved to be spontaneous. Also, the adsorbent was regenerated and reused for five cycles. This study shows that AC@Al could be used as a cost-effective adsorbent.

In this study, a new composite adsorbent, namely magnesium oxide modified graphene oxide (hereafter abbreviated GO@MgO), was prepared for the removal of Ibuprofen (IBU), a non-steroidal anti-inflammatory drug (NSAID) compound. Graphene oxide was modified with MgO to improve its properties. Several factors important for the evolution of the adsorption process were investigated, such as the dose of the adsorbent, the pH, and the initial IBU content, as well as the duration of the procedure and temperature. According to the results obtained, it was found that at pH 3.0 ± 0.1, by applying 0.5 g/L GO@MgO to 100 mg/L IBU, more than 80% was removed, reaching 96.3% with the addition of 1.5 g/L adsorbent in 24 h. After 30 min, the equilibrium was reached (77% removal) by adding 0.5 g/L of GO@MgO. This study proves that GO@MgO is capable of economical and efficient adsorption. The IBU kinetic data followed the pseudo-second-order kinetic model. Langmuir and Freundlich isotherm models were used to interpret the adsorption, but the Freundlich model described the adsorption method more accurately. The positive values of ΔH⁰ (14.465 kJ/mol) confirm the endothermic nature of the adsorption. Due to the increase of ΔG⁰ values with temperature, the adsorption of IBU on GO@MgO is considered to be spontaneous.

Hexavalent chromium (Cr (VI)) contamination of water resources constitutes a major environmental and public health issue due to its high toxicity, mobility, and carcinogenic properties. This review examines recent advances in Cr (VI) removal technologies from water and wastewater, with emphasis on membrane-based separation processes and adsorption approaches. Conventional treatment methods, including chemical precipitation, ion exchange (IX), electrocoagulation (EC), electrodeionization (EDΙ), bioremediation, and photocatalysis, are comparatively discussed in terms of removal efficiency, operational limitations, and applicability. In parallel, sustainable adsorbent materials derived from biomass and agricultural waste are evaluated as environmentally friendly and cost-effective alternatives for chromium removal. The role of functional groups, adsorption mechanisms, and redox interactions involved in Cr (VI) reduction and immobilization is also analyzed. Attention is given to membrane technologies, such as reverse osmosis (RO), nanofiltration (NF), electrodialysis (ED), and ultrafiltration (UF) after surface modification with the incorporation of nanomaterials and/or the application of Layer-by-Layer (LBL) assembly techniques, which enhance selectivity, permeability, and antifouling behavior. The reviewed studies demonstrate that advanced membrane systems and bio-based adsorbents can achieve high chromium removal efficiencies while supporting sustainable water treatment practices. Overall, the combination of membrane technologies with functionalized materials represents a promising direction for the development of efficient and environmentally sustainable Cr (VI) remediation systems capable of meeting increasingly strict regulatory limits.