Anissa Somrani

An efficient method for nitrate removal from water was developed using the sea plant Posidonia oceanica (L.) as a biosorbent. Never used previously for this purpose, this plant was applied in its natural form without any chemical modification or cross-linking with another material. The nitrate biosorption was carried out in batch experiment at room temperature and under the optimum conditions of agitation time, biosorbent dose, and pH. The Langmuir model fits the experimental biosorption isotherm data better than the Freundlich one, confirming a monolayer adsorption process onto homogeneous surface and giving a relatively high maximum biosorption capacity 41.6 mg · g - 1 of nitrate nitrogen, thus demonstrating a good efficiency of the biosorbent. The thermodynamic study shows not only that the biosorption process is spontaneous and endothermic in nature, but also that increasing temperature enhances the nitrate uptake. Furthermore, the Dubinin–Radushkevich modeling gives a mean free energy of 15.81 kJ · mol - 1 , indicating that nitrate was chemisorbed. The same result was confirmed by kinetic modeling, which showed that the pseudo-second-order model fits the experimental data better than the pseudo-first order. The characterization by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) revealed that nitrate was mainly retained on the biosorbent surface through electrostatic forces with protonated amines ( RNH 3 + ; R 2 NH 2 + and R 3 NH + ). However, ion exchange with hydroxide ions and intraparticle diffusion may play an important role in the biosorption process.

As sensitive parts of the water treatment process, reverse osmosis (RO) membranes are the most important for desalination and wastewater treatment. But the performance of RO membranes deteriorates over time due to fouling, necessitating frequent replacements. One of the environmental challenges is the disposal of End-of-Life (EoL) RO membranes, which are made of non-biodegradable polymers. The reuse of EoL membranes as a sustainable approach for waste saving and resource efficiency has recently attracted considerable attention. The present work provides a comprehensive overview of the strategies for reusing EoL RO membranes as sustainable alternatives to conventional disposal methods. Furthermore, the fundamental principles of RO technology, the primary types and impacts of membrane fouling, and advanced cleaning and regeneration techniques are discussed. The conversion of EoL membranes into nanofiltration (NF), ultrafiltration (UF), and forward osmosis (FO) membranes is also covered in this review, as well as their uses in brackish water desalination, dye/salt separation, groundwater treatment, and household wastewater reuse. Environmental and economic benefits, as well as technical, social, and regulatory challenges, are also discussed. Finally, the review highlights innovative approaches and future directions for incorporating EoL membrane reuse into circular economy models, outlining its potential to improve sustainability and reduce operational costs in water treatment systems.

In this study, we explore the possibility of reusing end-of-life seawater reverse osmosis (RO) membranes to treat brackish water and industrial effluent. Prior to cleaning the end-of-life RO membranes, we conducted several autopsies in order to assess the extent of degradation. Based on these results, three cleaning protocols were tested and Ultrasil10 and/or chlorine solution were selected for further investigation. The cleaning capacity of the chlorine treatment at 4000 ppm.h was tested but proved inefficient as it leads to a denser cake and a significant decrease in hydraulic permeability. Therefore, we recommend commencing chemical cleaning with Ultrasil10 to remove foulants, thereby reconditioning the end-of-life RO membranes to meet nanofiltration membrane specifications. The cleaned end-of-life RO membranes exhibited enhanced hydraulic permeability (1.97 L·h⁻¹·m⁻²·bar⁻¹) and achieved a salt rejection of 85% for brackish water (6 g/L NaCl). With a molecular weight cutoff of 86 Da, these membranes effectively reduced brackish water conductivity to below 1000 µS/cm at 10 bars, complying with Tunisian drinking water standards (300–2500 µS/cm). Additionally, they demonstrated high efficiency in treating industrial effluents, achieving turbidity levels below 2 NTU and conductivity of 180 µS/cm. Operating at lower pressures, these membranes provided cost-effective, sustainable solutions and performed comparably to commercial new NF membranes, validating their potential for reuse in brackish water and wastewater treatment applications.

The objective of this study is to evaluate the degradation of end-of-life BWRO membranes sourced from a factory in France by analyzing their water permeability, roughness, and chemical composition in order to diagnose the level of degradation incurred during their first life cycle in water softening. Following this, two new applications for the end-of-life BWRO membranes were investigated: (i) as ultrafiltration membranes (UF) for domestic effluent treatment and (ii) as cation exchange membranes (CEM) for use in fungal microbial fuel cells (FMFC). The UF membrane was renovated with an acetic acid treatment and, subsequently, used for domestic effluent filtration. The cation exchange membrane was developed in two steps: (i) chlorine treatment and (ii) the deposition of an Amer Sil layer, a functional coating formed by an interpenetrating polymer network (IPN) made of sulfonated polyether sulfone (S-PES) in a cross-linked matrix of acrylic acid and divinylbenzene.

We have investigated the use of chitosan for aluminium removing from (Li⁺–Al³⁺) aqueous solutions. The isotherms and kinetics of adsorption with respect of initial aluminium concentration and pH were investigated. The optimum pH value for quantitative adsorption is 4. Langmuir and Freundlich adsorption models were applied to describe the experimental isotherms. Three simplified kinetics models, based on first-order, pseudo second-order and Elovich equations, were tested to describe the adsorption mechanism.