Initial Sodium Dodecyl Sulfate Research Articles

Wetting of aqueous sodium dodecyl sulfate droplets on polydimethylsiloxane surfaces during evaporation

Wetting of aqueous sodium dodecyl sulfate (SDS) droplets on polydimethylsiloxane (PDMS) surfaces during evaporation were experimentally studied. After a short-time spontaneous spreading, sessile droplets experienced a period of the constant contact radius (CCR) stage. And it was found that substrate elasticity was found to have an influence on the duration of the CCR stage during the evaporation of aqueous SDS droplets on PDMS surfaces. Moreover, a local contact angle minimum was found during the evaporation of aqueous SDS droplets with an initial SDS concentration below 0.5 CMC. A physical mechanism taking into account the structure of SDS molecules adsorbed at PDMS surfaces was developed for the occurrence of the CCR stage and the local contact angle minimum. Furthermore, two-third power of the instantaneous droplet volume nearly varies linearly with time for all cases.

Evaporative Deposition of Surfactant-Laden Nanofluid Droplets over a Silicon Surface.

Morphologies of evaporative deposition, which has been widely applied in potential fields, were induced by the competition between internal flows inside evaporating droplets. Controlling the pattern of deposition and suppressing the coffee-ring effect are essential issues of intense interest in the aspects of industrial technologies and scientific applications. Here, evaporative deposition of surfactant-laden nanofluid droplets over silicon was experimentally investigated. A ring-like deposition was formed after complete evaporation of sodium dodecyl sulfate (SDS)-laden nanofluid droplets with an initial SDS concentration ranging from 0 to 1.5 CMC. In the case of initial SDS concentrations above 1.3 CMC, no cracks were observed in the ring-like deposition, indicating that the deposition patterns of nanofluid droplets could be completely changed and cracks could be eliminated by sufficient addition of SDS. With the increase of the initial concentration of hexadecyl trimethylammonium bromide (CTAB), the width of the deposition ring gradually decreased until no ring-like structure was formed. On the contrary, with the increase of the initial Triton X-100 (TX-100) concentration, the width of the deposition ring gradually increased until a uniform deposition was generated. Moreover, when the initial TX-100 concentration was high, a "tree-ring-like" pattern was discovered. Besides, morphologies of evaporative pattern due to the addition of surfacants were qualitatively analyzed.

Wettability and evaporation of dilute sodium dodecyl sulfate droplets on micropillar-arrayed non-wetting surfaces

Wettability and evaporation of dilute sodium dodecyl sulfate (SDS) droplets on micropillar-arrayed polydimethylsiloxane (PDMS) were experimentally studied. It was found that the apparent, advancing and receding contact angles all decreased with the increase of initial SDS concentration and wettability of dilute SDS droplets depended on both SDS concentration and surface roughness. Due to the adhesion between the droplets and the micropillars, all evaporation began with constant contact radius (CCR) mode. It is more interesting that short-time spontaneous spreading was found to follow the CCR stage for dilute SDS droplets evaporating on the patterned surface with sparser micropillars, which can be attributed to the transition from the Cassie-Baxter wetting state to the Wenzel wetting state (CB-W transition). Such a transition has been experimentally observed and a theoretical model was developed to qualitatively elucidate the spontaneous spreading.

Sodium Dodecyl Sulfate Adsorption on Sulfuric Acid-Crosslinked Chitosan/Pectin Polyelectrolyte Complex Film

Sulfuric acid cross-linked chitosan/pectin polyelectrolyte complex (CPS) film was prepared as sodium dodecyl sulfate (SDS) adsorbent. CPS films were prepared in various compositions of chitosan/pectin and cross-linked by immersion in 0.1 M H2SO4 solution. CPS films were characterized using FTIR and SEM. CPS film was used for SDS adsorption with parameters of film composition, contact time, pH, initial SDS concentration. FTIR spectra showed characteristic peaks for chitosan, pectin and their interaction with sulfuric acid. The surface of the CPS film changed to become smoother after being used for SDS adsorption. CPS film composition 70:30 showed the highest percent swelling and was stable at the overall pH. The optimum conditions for SDS adsorption by sulfuric acid cross-linked chitosan/pectin CPS film occurred at a contact time of 120 minutes, pH 5, initial concentration of SDS 100 mg L–1 with a film composition of 70:30. Adsorption followed the pseudo-second-order kinetic and Freundlich isotherm models with KF and n of 0.0297 and 0.377, respectively. The highest SDS desorption of 97.6% was achieved using 0.1 M NaClO4 solution.

The effect of prolonged exposure on sodium dodecyl sulfate penetration into human skin

The purpose of this study was to examine the effect of prolonged surfactant exposure on mechanisms of anionic surfactant penetration into human skin. A radiolabeled probe (14-carbon sodium dodecyl sulfate (14C-SDS)) was used to trace the penetration of a model anionic surfactant, sodium dodecyl sulfate (SDS), into excised human skin and into an inert membrane composite in vitro. SDS dose varied from 0.03 to 15 mg/cm2, mimicking the exposure of a rinse-off cleanser on skin. Two surfactant exposure lengths were tested, 2 min and 5 h. SDS penetration into excised human skin was constant from 50 to 600 mM for skin samples exposed to SDS for 2 min. For skin samples exposed to SDS for 5 h, SDS penetration into skin increased log-linearly with increasing SDS concentration. SDS penetration into the inert membrane composite was constant from 50 to 600 mM SDS regardless of length of surfactant exposure. Penetration of the radiolabeled probe into skin and into the inert membrane correlated well with the monomeric concentration of the radiolabeled probe in the applied surfactant solution. These results support that monomer concentration is the driving force for initial SDS penetration into upper layers of the stratum corneum over a wide range of concentrations. With prolonged exposure, SDS penetrates the skin in a dose-dependent manner due to surfactant-induced damage to the skin.

Revisiting OPLS-AA Force Field for the Simulation of Anionic Surfactants in Concentrated Electrolyte Solutions.

Hereby, we developed a set of nonbonded parameters within all-atom optimized potentials for liquid simulations (OPLS-AA) force field for the simulation of concentrated electrolyte solutions of anionic surfactants. More specifically, the aim of this paper is to assess the performance of five sets of atomic charges calculated using different population analyses (DDEC6, CHelpG, CHelpG-SMD, RESP, and CM5), as well as the original set of charges used in the literature for sodium dodecyl sulfate (SDS) simulation. Recently, Farafonov et al. have revised the SDS OPLS-AA force field; however, we were unable to obtain the experimental rodlike micelles using this parameter set on long time scale. In fact, the initial SDS bilayer micelle adopted a rodlike shape transiently and then broke down into spherical micelles. Updating OPLS-AA force field with DDEC6, CHelpG, and CHelpG-SMD charges resulted in stable rod micelles for a long simulation time (1 μs). The atomic charges of Farafonov (taken from Shelley et al.), RESP, and CM5 could not correctly describe SDS in concentrated electrolyte solutions. Analysis of the interaction of SDS with the counterions and solvent highlights the role of a balance of the intermolecular forces that must be met to describe adequately the anionic surfactant electrolyte solutions. Further, the optimization of the SDS Lennard-Jones parameters enabled the Farafonov set to properly reproduce the experimental rod micelle. In addition, we have examined the performance of different parameters of sodium ions: the first developed based on the Kirkwood-Buff integrals (KBI) and the second developed by Joung et al. The excessive ion pairing caused by KBI parameters screens significantly SDS-water interactions, which stabilize the rod micelle. Further, a tight interaction of the Na+-SDS head group resulted in stabilization of the bilayer micelle as observed in the case of Na+ parameters developed by Joung et al.

Evaporation of Dilute Sodium Dodecyl Sulfate Droplets on a Hydrophobic Substrate.

Evaporation of surfactant-laden sessile droplets is omnipresent in nature and industrial applications such as inkjet printing. Soluble surfactants start to form micelles in an aqueous solution for surfactant concentrations exceeding the critical micelle concentration (CMC). Here, the evaporation of aqueous sodium dodecyl sulfate (SDS) sessile droplets on hydrophobic surfaces was experimentally investigated for SDS concentrations ranging from 0.025 to 1 CMC. In contrast to the constant contact angle of an evaporating sessile water droplet, we observed that, at the same surface, the contact angle of an SDS laden droplet with concentration below 0.5 CMC first decreases, then increases, and finally decreases, resulting in a local contact angle minimum. Surprisingly, the minimum contact angle was found to be substantially lower than the static receding contact angle and decreased with decreasing initial SDS concentration. Furthermore, the bulk SDS concentration at the local contact angle minimum was found to decrease with decrease in the initial SDS concentration. The location of the observed contact angle minimum relative to the normalized evaporation time and its minimum value proved to be independent of both the relative humidity and droplet volume and thus of the total evaporation time. We discuss the observed contact angle dynamics in terms of the formation of a disordered layer of SDS molecules on the substrate at concentrations below 0.5 CMC. The present work underlines the complexity of the evaporation of sessile liquid-surfactant droplets and the influence of surfactant–substrate interactions on the evaporation process.

Degradation of anionic surfactant in municipal wastewater by UV-H2O2: Process optimization using response surface methodology

This study reports the degradation of sodium dodecyl sulfate (SDS) – an anionic surfactant in wastewater, using a UV based advanced oxidation process. Kinetic experiments were conducted for both municipal wastewater and distilled water-spiked samples containing 100 mg L−1 of SDS. The fluence based, pseudo-first-order reaction rate constant for wastewater sample was found to be 1.5 times lesser than distilled water-spiked sample. The treatment process was optimized by response surface methodology (RSM) using central composite designs (CCD) approach. Effects of process parameters like reaction time, hydrogen peroxide dose, initial SDS concentration and UV absorbance of wastewater at 254 nm (UVA254) were studied on degradation of SDS. Results indicate that an increase in reaction time shows an increase in the rate of degradation of SDS; whereas, initial SDS concentration and UVA254 showed a significant decrease. On the other hand, degradation of SDS increased with increase in H2O2 dose and then decreased with further increase in peroxide dose depending upon initial SDS concentration. The maximum SDS degradation was determined by the quadratic model and the predicted degradation percentage of SDS was about 81% for a reaction time of 7 min with initial SDS concentration of 200 mg L-1, H2O2 dose of 2.0 mol of H2O2/mol of SDS and UVA254nm of 0.19. Further, the biodegradability of the SDS-spiked wastewater was evaluated for the UV-H2O2 treated samples.

Removal of alkali metal ions from aqueous solution by foam separation method

Foam separation method can effectively remove alkali metal ions from anionic surfactant solution by a combination of an air bubble generator and the flotation system. The alkali metal ions in the solution electrostatically adsorb onto the many bubbles by bubbling ionic surfactant solution and they transfer to the air/water interface. These bubbles change to the foam state that is removed using a long glass tube. The typical experimental system was composed of sodium dodecyl sulfate (SDS) as an anionic surfactant and the target alkali ions (Li, K, Rb, and Cs). Therefore, selective competition for air bubbles exists between the sodium (counterion of the surfactant) and target alkali ions. The removal rate of the alkali metal was noticeably dependent on surfactant concentration. The surfactant was effective in removing the alkali metal below the critical micelle concentration (CMC). The removal rate increased with increasing atomic number or crystal ion radius: Li < K < Rb < Cs. The best removal rate of the alkali metals involved 80% Cs elimination by using a microbubble generator (5 h) at the initial SDS concentration of 4 mmol/L and Cs 2.5 mmol/L. On the other hand, the removal rates of dodecylsulfate and counterion (Na) respectively decreased to 25% and 42% for the system. These results indicated that Cs was more selectively adsorbed onto the bubble than Na. A smaller hydration radius can easily bind the surfactant sulfate ions. This study showed that the foam separation method could selectively remove hazardous metals from contaminated water.

Preparation of Magnetic Multi-Walled Carbon Nanotubes to Adsorb Sodium Dodecyl Sulfate (SDS)

Surfactants are one of the main groups of pollutants released into aqueous solutions due to human activities and their harmful effects have been proven on human. In this study, first, magnetic multi-walled carbon nanotubes (MMWCNTs) were synthesized and then, the effects of operating parameters such as surfactant concentration, adsorbent dosage, and pH values were analyzed on the adsorption process. MMWCNTs were characterized by means of X-ray diffraction (XRD) analysis and fourier transform infrared spectroscopy (FTIR). The optimal adsorption conditions were achieved at initial pH = 4.6, adsorbent concentration = 0.5 g/L, and initial SDS concentration = 15 mg/L. In addition, the equilibrium of sorption reached after 120 min and the maximum capacity of SDS for monolayer coverage was found to be 61 mg/g at 25°C. Kinetic studies were performed under optimal conditions and the sorption kinetics was described using the pseudo-second-order kinetic model. The experimental data were studied using Freundlich, Langmuir, and Sips models. Finally, the experimental data were fitted reasonably by Langmuir isotherm. The results demonstrated that MMWCNTs with respect to their high adsorption capacity, relatively low equilibrium time, and capability to be separated from aqueous solutions (after adsorption) could be applied to wastewater treatment.

Evaporation Dynamics of Mixed-Nanocolloidal Sessile Droplets.

Evaporation dynamics of a particle-laden droplet has been a topic of interest in recent times owing to its widespread applications, ranging from surface patterning to drug delivery systems. The interplay of evaporation-induced internal flow dynamics, contact line dynamics, and nanoparticle self-assembly govern the morphologies of the residual structures. Fine-tuning of these residual structures is thus possible by controlling the governing parameters. A nanoparticle-laden sessile droplet placed on a hydrophobic substrate undergoes buckling phenomenon that results in a domelike structure with cavity on the surface. In the present work, it is shown that the addition of sodium dodecyl sulfate (SDS) surfactant in minute concentrations (0.005-0.02 wt %) can affect the contact line dynamics and subsequent buckling dynamics of a nanoparticle-laden droplet evaporating on a hydrophobic substrate. With increase in the initial SDS concentration, the morphologies of the residual structures show transition from a buckled dome structure to a flat flowerlike shape. Moreover, a critical SDS concentration (>0.0075 wt % in 20 wt % silica) is identified for the complete suppression of buckling instabilities. Last, the effects of droplet spreading on the surface crack dynamics are discussed.

Interaction between a hydrophobic rigid face and a flexible alkyl tail: Thermodynamics of self-assembling of sodium cholate and SDS

The thermodynamics of molecular self-assembling of an anionic biosurfactant, sodium cholate (NaCA) and its mixtures with sodium dodecyl sulfate (SDS) in aqueous solution have been investigated by isothermal titration calorimetry (ITC), along with fluorescence and conductivity measurements. Different critical concentrations were obtained by these three techniques – critical pre-micelle concentration (cmcpre) and critical micelle concentration (cmc) for pure NaCA, and critical micelle concentrations (cmcmix) for the mixed systems with differently initial SDS concentrations. Importantly, ITC allowed us to directly measure the enthalpy changes of pre-micelle formation (ΔHpremic=(−0.28±0.02)kJ·mol−1) and of micelle formation (ΔHmic=(−1.76±0.05)kJ·mol−1) for pure NaCA as well as the enthalpies for micellization for the mixed systems NaCA/SDS. The non-ideality of the mixed surfactant solution was evaluated in terms of interaction parameters and excess enthalpies that were calculated in the light of Clint’s and Rubingh’s models. It was found that there is an obvious synergistic effect in the NaCA/SDS mixed system. From all these results we can ascribe the strong interaction between the same charge surfactants NaCA and SDS to the structural difference in their hydrophobic moieties. In fact, the flexible alkyl chains of SDS and the non-planar hydrophobic β-faces of NaCA tend to have a more compact packing than pure NaCA.

Application of micellar enhanced ultrafiltration (MEUF) process for zinc (II) removal in synthetic wastewater: Kinetics and two-parameter isotherm models

Micellar enhanced ultrafiltration (MEUF) of zinc(II) from synthetic wastewater using sodium dodecyl sulfate (SDS) at low concentration was carried out in lab scale membrane system. Initial SDS concentration below critical micelle concentration (CMC) showed marginal increment and sharp reduction in zinc(II) removal percentage above CMC. Zinc(II) removal percentage decreased from 84.67 to 82.42% when the initial zinc(II) concentration increases from 0.42 to 2.10 mM at constant SDS concentration. Various performance parameters, i.e., amount of SDS micelles, gross of surfactant, ratio of S′ to M′ (i.e., molar ratio of the SDS micelle to the zinc(II) ions), average concentration factor, volume concentration ratio, and system conversion, as function of initial SDS concentration were investigated. Pseudo-second-order kinetic equation could be used to elucidate kinetics, while Freundlich two-parameter isotherm model was apposite to describe zinc(II) adsorption on SDS micelles. Further, distribution coefficient of zinc(II) ions in micellar and aqueous pseudo-phases, micelle loading, and micelle binding constant were estimated to evaluate MEUF process.

Micellar enhanced ultrafiltration (MEUF): activated carbon fiber (ACF) hybrid process using low surfactant concentration for zinc(II) removal from synthetic wastewater

Zinc(II) removal from synthetic wastewater by micellar enhanced ultrafiltration (MEUF) using low sodium dodecyl sulfate (SDS) concentration and 300 kDa molecular weight cut-off (MWCO) membrane was studied. Effects of various parameters like initial permeate flux, retentate pressure, molar ratio of zinc(II) to SDS, initial zinc(II) concentration, MWCO, and solution pH were analyzed. Considering zinc(II) removal rate and permeate flux, initial permeate flux of 43.64 L/m2 h, retentate pressure of 0.20 MPa, molar ratio of zinc(II) to SDS of 1:2, and neutral pH condition were found to be optimum operating parameters. Although initial SDS concentrations were far below critical micelle concentration, average zinc(II) removal rate was 77.29 and 75.93% whereas, absolute permeate flux was 39.64 and 10.45 L/m2 h at molar ratios of zinc(II) to SDS of 1:8 and 1:2, respectively. It was observed that concentration polarization played a crucial role in zinc(II) removal. In MEUF-ACF hybrid process at constant initial zinc(II) concentration (0.42 mM) and initial SDS concentration (0.21 mM), average zinc(II) removal rate was 8.65, 12.70, 10.84%, while SDS removal rate was 10.5, 12.6, 11.52% higher than MEUF alone in 30, 100, 300 kDa membranes, respectively.

Photocatalytic Fenton oxidation of sodium dodecyl sulfate solution using iron-modified zeolite catalyst

The heterogeneous photo-Fenton oxidation of sodium dodecyl sulfate (SDS) solutions was investigated in a quartz batch reactor using an artificial UV light source. Fe-modified zeolite was used as a heterogeneous catalyst in the process. The effect of various process variables on SDS removal performance was evaluated by examining temperature, pH, H2O2 dosage, catalyst loading, initial SDS concentration and light intensity. The optimal operational parameters were found as follows: temperature 35°C, solution pH 7.5, 15 mmol H2O2 dosage, and 1 g/L catalyst loading. Stability and the reuse of the catalyst were also tested. Comparison with homogenous photo-Fenton process was also performed by analyzing SDS removal rate. Kinetic investigation of removal process based on different kinetic models was evaluated. The results showed that the first-order kinetic model was in good correlation with experimental data.

Equilibrium and kinetic studies of the adsorption of sodium dodecyl sulfate from aqueous solution using bone char

In this study, bone char (BC) was used as an adsorbent for sodium dodecyl sulfate (SDS) in aqueous solution. Batch studies were performed to address various experimental parameters like contact time (0–360 min), adsorbent dosage (3, 5 and 7 g/L), initial SDS concentration (0.5, 1 and 2 mg/L) for the removal of the SDS. A greater percentage of SDS was removed with a decrease in its initial concentration, and an increase in the amount of adsorbent used. The maximum removal percentage of SDS for 0.5, 1 and 2 mg/L were estimated 80.2, 76 and 60.5 %. The maximum removal of SDS was obtained in the adsorbent dose of 7 g/L. Equilibrium isotherms were analyzed by Freundlich and Langmuir isotherm equations. The Freundlich equation is found to best represent the equilibrium data for the adsorption system. The kinetic study showed that the adsorption of SDS on BC was a gradual process. Pseudo-first order, pseudo-second order, Eluvich and intraparticle diffusion models were used to fit the experimental data. The intraparticle diffusion model was able to provide realistic description of adsorption kinetics.

Protein Structural Change in a Mixed System of Ionic and Zwitterionic Surfactants

The secondary structure of bovine serum albumin (BSA) in the binary surfactant system of anionic sodium dodecyl sulfate (SDS) and zwitterionic N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (DDAPS) was examined at 25°C. The helicity of BSA decreased from 66% to 55% in a solution of DDAPS alone and decreased to 50% in a solution of SDS alone. However, the late addition of DDAPS reformed the helical structure of BSA, which was initially disrupted by SDS. The reformation required higher DDAPS concentrations as the initial SDS concentration increased. A maximum helicity of 63% was attained by this reformation. On the other hand, the helical structure of the protein, which was first affected by DDAPS denaturation, was also reformed to the same degree by the late addition of certain amounts of SDS. Although attention was paid to the additive order of these two surfactants to BSA, the final helicity of the protein depended on the final concentrations of these two surfactants, irrespective of the additive order. These phenomena may be attributed to the predominance of mixed micelle formation over complex formation between BSA and the two surfactants below the mixing ratio of DDAPS ([DDAPS]/([DDAPS]+[SDS])) of 0.95. The predominance of the mixed micelle formation distinctly appeared in mixing ratios between 0.50 and 0.75. In this range, the mixed micelle formation accompanied the removal of dodecyl sulfate (DS) ions bound to BSA upon the late addition of DDAPS to the BSA-SDS mixture, whereas, upon the late addition of SDS to the BSA-DDAPS mixture, the mixed micelle formation was accelerated by the coexistence of DDAPS which disturbed the binding of DS ions to the protein.

Micellar-enhanced ultrafiltration of cadmium and methylene blue in synthetic wastewater using SDS

Single and simultaneous removal of Cd 2+ and methylene blue (MB) with sodium dodecyl sulfate (SDS) by micellar-enhanced ultrafiltration under different experimental conditions was investigated. In single removal process, with initial SDS concentration increasing, the removal efficiency of Cd 2+ and MB kept increasing and then decreased. When the initial concentrations of SDS and Cd 2+ were 1.0 cmc and 50 mg L −1, respectively, the maximum removal efficiency of Cd 2+ was obtained as 99.2%. Removal efficiency of MB could achieve more than 99.9% with initial SDS concentration below 2.0 cmc. As compared with single Cd 2+ removal, the removal efficiency of Cd 2+ in the presence of MB was slightly higher with initial SDS concentration below 1.0 cmc, while decreased with the SDS concentration above 1.0 cmc. The maximum removal efficiency of Cd 2+ was 98.8% when initial concentrations of SDS and MB were 1.0 cmc and 4 mg L −1, respectively. The removal efficiency of MB in the presence of Cd 2+ could achieve higher than 96.5%, which was only 3.4% less than the optimum result of the single removal. Meanwhile, effect of pH on removal efficiency of Cd 2+ was more significant than that of MB.

Equilibrium Distribution Model of Betaine between Surfactant Micelles and Water: Application to a Micellar-Enhanced Ultrafiltration Process

The aim of this work was to determine the optimal surfactant concentration and operating conditions for betaine recovery from aqueous solutions by micellar-enhanced ultrafiltration (MEUF). Initial centrifugal ultrafiltration experiments with commercial 5 kDa cutoff polyethersulfone membranes showed that optimal betaine extraction was achieved with 200 mol/m3 of sodium dodecyl sulfate (SDS) as surfactant, at pH 1, with phosphoric acid for pH adjustment. The degree of betaine extraction increased with SDS concentration but remained constant with increasing betaine concentration for a given initial SDS concentration. The equilibrium distribution constants, KS, of betaine between SDS micelles and water were determined assuming a theoretical pseudophase separation model. Continuous MEUF with a 5 kDa cutoff TiO2 tubular ceramic membrane was performed in order to concentrate the micellar solution. Complete rejection of the micelles by the membrane was observed, resulting in 54% of the betaine and 99% of the SDS in micellar form, in agreement with the values estimated using the proposed theoretical model.

Micellar-enhanced ultrafiltration for the removal of cadmium and zinc: Use of response surface methodology to improve understanding of process performance and optimisation

In this study, removal of cadmium and zinc from their respective water samples was conducted by micellar-enhanced ultrafiltration (MEUF), using sodium dodecyl sulfate (SDS) as the surfactant. Response surface methodology (RSM) was used for modelling and optimising the process, and to gain a better understanding of the process performance. Face Centred Composite (CCF) Design was used as the experimental design. The factors studied were pressure ( P), nominal molecular weight limit (NMWL), heavy metal feed concentration ( C Zn, C Cd) and SDS feed concentration ( C SDS). Using RSM the retention of heavy metals was maximized while optimising the surfactant to metal ratio (S/M). Response surface plots improved the understanding the effect of the factors on permeate flux. Concentration polarisation was negligible and therefore, high NMWL membranes with high pressure provided high flux with negligible effect on the retention of heavy metals. The optimal conditions of zinc removal were C SDS = 13.9 mM, C Zn = 0.5 mM, NMWL = 10 kDa and P = 3.0 bar, and for cadmium removal C SDS = 14.2 mM, C Cd = 0.5 mM, NMWL = 10 kDa and P = 3.0 bar. The retentions achieved were 98.0 ± 0.4% for zinc and 99.0 ± 0.4% for cadmium. To improve resource efficiency, the surfactant was reclaimed after use; 84% of the initial SDS was recovered by precipitation.