Removal of Organics with Ion-Exchange Resins (IEX) from Reverse Osmosis Concentrate

Abstract

Reverse osmosis concentrate (ROC) produced as the by-product of the reverse osmosis process consists of a high load of organics (macro and micro) that potentially cause eco-toxicological effects in the environment. Previous studies focused on the removal of such compounds using oxidation, adsorption, and membrane-based treatments. However, these methods were not always efficient and formed toxic by-products. The impact of ion-exchange resin (IEX) (Purolite®A502PS) was studied in a micro-filtration–IEX hybrid system to remove organics from ROC for varying doses of Purolite® A502PS (5–20 g/L) at a flux of 36 L/m2h. The purolite particles in the membrane reactor reduced membrane fouling, evidenced by the reduction of transmembrane pressure (TMP), by pre-adsorbing the organics, and by mechanically scouring the membrane. The dissolved organic carbon was reduced by 45–60%, out of which 48–81% of the hydrophilics were removed followed by the hydrophobics and low molecular weight compounds (LMWs). This was based on fluorescence excitation-emission matrix and liquid chromatography-organic carbon detection. Negatively charged and hydrophobic organic compounds were preferentially removed by resin. Long-term experiments with different daily replacements of resin are suggested to minimize the resin requirements and energy consumption.

Comparison of Coagulation-Integrated Sand Filtration and Ultrafiltration for Seawater Reverse Osmosis Pretreatment

“…For PAC, the removal rates were 82.4% for the HPO fraction and 47.5% for the HPI fraction, while for FeCl3, they were 85.5% for the HPO fraction and 45.5% for the HPI fraction. This differential removal efficiency is attributed to the higher charge density of the HPO fraction compared to the HPI fraction, leading to enhanced interactions between HPO and polyvalent metal ions, thereby increasing the effectiveness of traditional coagulation pretreatment [30,31]. Figure 4 depicts the content of hydrophilic, transphilic and hydrophobic fractions of DOM in unpretreated water samples, as well as those in water pretreated with 30 mg•L −1 PAC (referred to as Al-30) and 10 mg•L −1 FeCl3 (referred to as Fe-10).…”

Membranes in Water Reclamation: Treatment, Reuse and Concentrate Management

“…Figure 3 illustrates the integrated membrane–hybrid system, which combines the membrane process with physicochemical methods such as adsorption, ion exchange, coagulation, bioconversion, and catalysis [ 27 , 45 , 46 ].…”

“…Aeration and the particle size of adsorbents also play a critical role in reducing membrane fouling through abrasion and scouring [ 45 , 48 , 49 ].…”

“… Hybrid membrane systems integrated with physicochemical treatment methods (modified and redrawn from Devaisy et al [ 45 ]). …”

Highly Efficient Biosorption of Cationic Dyes via Biopolymeric Adsorbent-Material-Based Pectin Extract Polysaccharide and Carrageenan Grafted to Cellulosic Nonwoven Textile

“…These technologies have revealed deficiencies and limitations given their high investment and operating costs. The processes based on reverse osmosis and ion exchange have proved to be more interesting given their ability to recover pollutant products during their elimination from the effluents [ 22 , 23 , 24 ]. However, these processes as well as those of advanced oxidation are not economically feasible due to their investment and relatively high operating cost.…”