Removal of small neutral organic micropollutants by pilot-scale reverse osmosis membrane modification with a novel polymer

Introduction. The occurrence of organic micropollutants (OMPs) in aquatic ecosystems presents a significant risk to water security (Albergamo et al. 2019). Reverse osmosis (RO) membranes can effectively remove OMPs in drinking water applications (Alonso et al. 2024). However, conventional RO membranes still exhibit limitations in effectively rejecting certain small, neutral, and hydrophilic OMPs (An et al. 2023). In-situ modification with 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) was studied to improve the rejection of four small, neutral and hydrophilic OMPs with spiral wound BW30 RO modules through pilot-scale setup. Through a systematic experimental approach and comprehensive analysis, we elucidated the impact of TMSPMA modification on membrane performance and mechanisms of OMPs retention. Experimental/methodology. A pilot-scale RO setup was designed to perform in-situ modification of spiral wound membrane elements and subsequent filtration experiments. Water permeability and the rejection of 1H-benzotriazole (BTA), Tolyltriazole (TA), Phenylurea (PU), and Paracetamol (PCM), as well as NaCl were measured subsequently. SEM, XPS, and WCA were used to characterize membranes. Results and discussion. Compared with the pristine membrane, the TMSPMA modification noticeably enhanced the rejection of four OMPs (Figure 1 a,b). Before modification, the retention of BTA, TA, PU, and PCM was 85.7%, 95.3%, 96.4%, and 98.1%, respectively. After TMSPMA modification, there was an increase in rejection of 12.2% for BTA, 2.3% for TA, 1.2% for PU, and 1% for PCM compared with the BW30 element. The enhanced rejection of these neutral OMPs can be attributed to the improved steric exclusion, which can be confirmed by the correlation analysis of the rejection of BTA, TA, PU, and PCM with their molecular weight (Figure 1 c). In addition, hydrophobic interactions also play a role in these OMPs rejection. Interesting findings were that the sorption amount of BTA, TA, PU, and PCM on the BW30-TMSPMA membrane was lower than that on the BW30 membrane. These results indicated that the hydrophobic adsorption effects of four hydrophilic OMPs decreased due to the enhancement of hydrophobicity of the BW30 membrane after grafting TMSPMA

In-situ reverse osmosis membrane surface modification with novel polymers : rejection of small neutral organic micropollutant

Highly selective in-situ surface grafting approaches were designed to improve the rejection of 1H-benzotriazole (BTA) by a reverse osmosis (RO) membrane. A commercial FT30 membrane was grafted in-situ for the first time with 2-(diethylamino)ethyl methacrylate (DEAEMA) and 3-(trimethoxysilyl)propyl methacrylate (TMSPMA), respectively, and compared with the state-of-the-art polydopamine (PDA) modification method. The TMSPMA grafting enhanced the BTA rejection from 88.4% to 98.4%, with a minor drop in water permeability (0.3%) compared to the pristine membrane. The TMSPMA-grafted membrane performed considerably better than the DEAEMA- and PDA-modified membranes. The improved rejection after TMSPMA modification can be ascribed to enhanced steric exclusion and hydrophobic interactions. The boosted hydrophobicity of the TMSPMA-grafted membranes is the result of the hydrophobic nature of the propyl/methyl groups present in TMSPMA, resulting in an 11.3% and 8.8% higher selectivity of BTA compared to the pristine FT30 and PDA-coated membrane, respectively. The A/B ratio (i.e., which indicates the membrane selectivity to water against the solute) of the TMSPMA-grafted membrane increased by 9%, which is the highest enhancement compared to other modified materials reported in the literature until now. This new modification approach is thus highly promising for membrane functionalization to improve the rejection of small neutral organic micropollutants

In-situ modification of nanofiltration and reverse osmosis membranes for organic micropollutants and salts removal : a review

The thin film composite (TFC) polyamide (PA) nanofiltration (NF) and reverse osmosis (RO) membranes are the two of the most robust technologies for the removal of organic micropollutants (OMPs) for (waste) water treatment, and improving sodium chloride (NaCl) rejection for sea water desalination to tackle water scarcity. However, the neutral, smaller and polar OMPs are often ineffectively removed by commercial NF/RO membranes. In-situ NF and RO membrane surface modification is a promising and viable option for improving the rejection of OMPs in existing membrane-based treatment plants without changing the production process. However, there is a research gap in the retention of different groups of OMPs by in-situ modified NF and RO membranes. To fill the research gap in recent years, this current review comprehensively analyzed the impact of reported in-situ NF and RO membranes modification strategies on water permeability, the retention of OMPs grouped by size, hydrophobicity, and charge, and NaCl rejection, where the tradeoff between water/OMPs permeability and water/NaCl permeability received special emphasis. Furthermore, optimal modification strategies to improve OMPs rejection in different groups by NF and RO have been suggested

Effect and mechanism of solution flow rate during interfacial polymerization on morphology and performance of hollow fiber membranes

Interfacial polymerization (IP) using m-phenylenediamine and trimesoyl chloride (TMC) is an essential method for producing thin-film composite (TFC) membranes. Nevertheless, IP is highly sensitive to changes in process parameters, especially the TMC solutions flow rate during inside-out TFC hollow fibers (HF) production. Research on the impact of flow conditions (i.e., laminar vs. turbulent flows) of these organic solutions on the final membrane characteristics and corresponding mechanism is still lacking. This research tested different TMC flow rates (0.1-2 mL/min) to produce inside-out TFC HF. With a TMC flow rate increase, (i) the leaf-like structures of the polyamide (PA) layer decreased in size, (ii) the thickness of the PA layer slightly increased, and (iii) the pure water permeability decreased. However, the elemental composition, chemical bonds, and NaCl rejection remained stable. Different fluid regimes are considered to affect the performance of HF membranes by affecting the heat dissipation process during IP reaction. A TMC flow rate in the laminar flow state (i.e., low flow rates) is recommended for synthesizing HFs. The current research provides new insights into the IP reaction mechanism of HF membrane, thus offering valuable guidance to optimize and produce membrane products with better performance

Phosphorus recovery by core-shell γ-Al2O3/Fe3O4 biochar composite from aqueous phosphate solutions

Biochar can act as an adsorbent for phosphate removal from water sources, which can be highly beneficial in limiting eutrophication and recycling elemental phosphorus (P). However, it is difficult to use a single biochar material to overcome problems such as low adsorption efficiency, difficulty in reuse, and secondary pollution. This study addresses these challenges using a novel core-shell structure &gamma;-Al2O3/Fe3O4 biochar adsorbent (AFBC) with significant P uptake capabilities in terms of its high adsorption capacity (205.7 mg g&minus;1), magnetic properties (saturation magnetization 24.70 emu g&minus;1), and high reuse stability (91.0% removal efficiency after five adsorption-desorption cycles). The highest partition coefficient 1.04 mg g&minus;1 &mu;M&minus;1, was obtained at a concentration of 322.89 &mu;M. Furthermore, AFBC exhibited strong regeneration ability in multiple cycle trials, making it extremely viable for sustainable resource management. P removal mechanisms, i.e., electrostatic attraction and inner-sphere complexation, were explained using Fourier transform infrared (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS) measurements. A surface complexation model was established by considering the formation of monodentate mononuclear and bidentate binuclear surface complexes of P to illustrate the adsorption process. Owing to its high adsorption efficiency, easy separation from water, and environmental friendliness, AFBC is a potential adsorbent for P recovery from polluted waters.</p

In-situ surface modification of a reverse osmosis membrane with acrylic polymers : transport and retention of a small neutral organic micropollutant

Highly selective in-situ surface grafting approaches were designed to improve the rejection of 1H-benzotriazole (BTA) by a reverse osmosis (RO) membrane. A commercial FT30 membrane was grafted in-situ for the first time with 2-(diethylamino)ethyl methacrylate (DEAEMA) and 3-(trimethoxysilyl)propyl methacrylate (TMSPMA), respectively, and compared with the state-of-the-art polydopamine (PDA) modification method. The TMSPMA grafting enhanced the BTA rejection from 88.4% to 98.4%, with a minor drop in water permeability (0.3%) compared to the pristine membrane. The FT30-TMSPMA membrane performed considerably better than the FT30-DEAEMA and FT30-PDA membranes. The improved rejection after TMSPMA modification can be ascribed to enhanced steric exclusion and hydrophobic interactions. The boosted hydrophobicity of the FT30-TMSPMA membranes is the result of the hydrophobic nature of the propyl/methyl groups present in TMSPMA, resulting in an 11.3% and 8.8% higher selectivity of BTA compared to the pristine FT30 and FT30-PDA membrane, respectively. The A/B ratio (which indicates the membrane selectivity to water against the solute) of the FT30-TMSPMA membrane increased by 714%, which is the highest enhancement compared to other modified materials reported in the literature until now. This new modification approach is thus highly promising for membrane functionalization to improve the rejection of small neutral organic micropollutants