Repeating recovery and reuse of SDS micelles from MEUF retentate containing Cd2+ by acidification UF

Effective Detoxification of Olive Mill Wastewater Using Multi-Step Surfactant-Based Treatment: Assessment of Environmental and Health Impact

Olive mill wastewater (OMW) poses a significant environmental challenge and health concern in olive-producing countries, including Jordan. Surfactant micelles are frequently employed as solubilizing agents to enhance the water solubility of chemical compounds. This study aims to leverage the sodium dodecyl sulfate (SDS) micelles in a multi-step process to detoxify OMW for agricultural and industrial uses and reduce its impact. The OMW was treated in multiple steps: screening, coagulation with different chemicals, and distillation with different surfactants. The treatment steps were monitored using LC-MS, GC-MS, ICP-MS, chemical oxygen demand contents, and total phenolic compounds. The detoxification of OMW was evaluated using standard germination assays, MTT assays using tissue culture, and toxicity assays using fluorescence bacteria. Following the treatment, the seed growth rate improved significantly from 0% to 100%. The GC-MS revealed a substantial decrease in pollutants. The concentration of polyphenols was reduced to 2.5%, while the COD level decreased to 35%. The toxicity in bacteria was significantly reduced in a time-dependent manner, and the toxicity in human cells decreased by 95%. Additionally, between 50% and 95% of metals in OMW were removed. The multi-step SDS-based approach successfully detoxified the OMW and enhanced water quality, which would pave the road for its direct application in industry and agriculture.

Microbial strategies for copper pollution remediation: Mechanistic insights and recent advances

Environmental contamination is aninsistent concern affecting human health and the ecosystem. Wastewater, containing heavy metals from industrial activities, significantly contributes to escalating water pollution. These metals can bioaccumulate in food chains, posing health risks even at low concentrations. Copper (Cu), an essential micronutrient, becomes toxic at high levels. Activities like mining and fungicide use have led to Copper contamination in soil, water, and sediment beyond safe levels. Copper widely used in industries, demands restraint of heavy metal ion release into wastewater for ecosystem ultrafiltration, membrane filtration, nanofiltration, and reverse osmosis, combat heavy metal pollution, with emphasis on copper.Physical and chemical approaches are efficient, large-scale feasibility may have drawbackssuch as they are costly, result in the production of sludge. In contrast, bioremediation, microbial intervention offers eco-friendly solutions for copper-contaminated soil. Bacteria and fungi facilitate these bioremediation avenues as cost-effective alternatives. This review article emphasizes on physical, chemical, and biological methods for removal of copper from the wastewater as well asdetailing microorganism's mechanisms to mobilize or immobilize copper in wastewater and soil.

A Prominent Streptomyces sp. Biomass-Based Biosorption of Zinc (II) and Lead (II) from Aqueous Solutions: Isotherm and Kinetic

Traditional freshwater sources have been over-abstracted in the worldwide crisis of water scarcity. Effluents have extremely high amounts of Zn2+ and Pb2+, according to an investigation of wastewater samples taken from several industrial zones. However, these heavy metals are among the most harmful to both humans and wildlife that are currently known. Streptomyces sp. is utilized in this study as a biosorbent to biosorb Zn2+ and Pb2+ from single and binary aqueous solutions. Several factors, such as biomass concentration (0.25–4 g), metal solution concentration (5–50 mg L−1), solution pH (2–5), and contact time were standardized. Streptomyces sp. biomass was able to extract 93% Pb2+ and 91% Zn2+ from a single and 95% Pb2+ and 97% Zn2+ from a binary metal aqueous solution containing 25 mg L−1 and pH 4. The highest adsorption capacity in both single and binary sorption experiments was determined to be shared by Zn2+ and Pb2+. The biosorbent’s metal adsorption increased from 0.48 to 4.56 mg g−1 for Pb2+ and from 0.21 mg g−1 to 4.65 mg g−1 for Zn2+ when the metals were present singly, and from 0.44 to 4.18 mg g−1 for Pb2+ and from 0.41 mg g−1 to 5.67 mg g−1 for Zn2+ when the metals were present in binary form. The amount of metal ions was raised from 5 to 50 mg L−1. Correlation coefficient (R2) values indicate that the adsorption pattern for Zn2+ and Pb2+ followed Freundlich isotherm R2 > 0.9543 for single and 0.9582 for binary sorption system. In order to remove Zn2+ and Pb2+ from an aqueous solution, Streptomyces sp. is a potential and different source of adsorbents.

Analysis of the process and factors influencing microbial phosphine production

The process of phosphine production by phosphate-reducing bacteria Pseudescherichia sp. SFM4 has been well studied. Phosphine originates from the biochemical stage of functional bacteria that synthesize pyruvate. Stirring the aggregated bacterial mass and supplying pure hydrogen could lead to an increase of 40 and 44% phosphine production, respectively. Phosphine was produced when bacterial cells agglomerated in the reactor. Extracellular polymeric substances secreted on microbial aggregates promoted the formation of phosphine due to the presence of groups containing phosphorus element. Phosphorus metabolism gene and phosphorus source analysis implied that functional bacteria used anabolic organic phosphorus, especially containing carbon-phosphorus bonds, as a source with [H] as electron donor to produce phosphine.

Electrolytes with Micelle-Assisted Formation of Directional Ion Transport Channels for Aqueous Rechargeable Batteries with Impressive Performance

Low-cost and ecofriendly electrolytes with suppressed water reactivity and raised ionic conductivity are desirable for aqueous rechargeable batteries because it is a dilemma to decrease the water reactivity and increase the ionic conductivity at the same time. In this paper, Li₂SO₄–Na₂SO₄–sodium dodecyl sulfate (LN-SDS)-based aqueous electrolytes are designed, where: (i) Na⁺ ions dissociated from SDS increase the charge carrier concentration, (ii) DS⁻/SO₄²⁻ anions and Li⁺/Na⁺ cations are capable of trapping water molecules through hydrogen bonding and/or hydration, resulting in a lowered melting point, (iii) Li⁺ ions reduce the Krafft temperature of LN-SDS, (iv) Na⁺ and SO₄²⁻ ions increase the low-temperature electrolyte ionic conductivity, and (v) SDS micelle clusters are orderly aggregated to form directional ion transport channels, enabling the formation of quasi-continuous ion flows without (r.t.) and with (≤0 °C) applying voltage. The screened LN-SDS is featured with suppressed water reactivity and high ionic conductivity at temperatures ranging from room temperature to −15 °C. Additionally, NaTi₂(PO₄)₃‖LiMn₂O₄ batteries operating with LN-SDS manifest impressive electrochemical performance at both room temperature and −15 °C, especially the cycling stability and low-temperature performance.

Solubilization and separation of o-toluidine and tricyclazole in sodium dodecyl sulfate micelles in micellar enhanced ultrafiltration

The solubilization laws of pollutants in micelles and their separation efficiency are very important in the successfully efficient application of micellar enhanced ultrafiltration (MEUF). The solubilization behavior of o-toluidine (OT) and tricyclazole (TC) into sodium dodecyl sulfate (SDS) micelles in MEUF was studied using nonlinear equation sets for concentration analysis, which resolved the issue on the overlap of absorption spectra of multicomponent compounds restricting the application of conventional ultraviolet (UV) spectroscopic method. The solubilization isotherms for both pollutants could be best explained by the Langmuir-Freudlich model (R²>0.99) followed by the modes of Langmuir and Freudlich, inferring the complexity of solubilization mechanism and solubilization advantage of monolayer over multilayer. The calculated thermodynamic parameters (ΔG⁰, ΔH⁰ and ΔS⁰) indicated that this process was endothermic and spontaneous. The solubilization of OT and TC well followed the pseudo second-order and pseudo first-order kinetics, respectively. The separation and recovery of SDS solubilizing these two pollutants were also investigated through lowering solution temperature to 2 °C followed by centrifugation. The best recovery rate of about 66% for SDS was achieved containing 10 and 5% of each initial amount of OT and TC, respectively, at near-neutral solution pH value. The recovery of SDS could decrease to some extent under alkaline and acidic conditions.

Determining binding of polycyclic aromatic hydrocarbons to micelles formed by SDS and SOL using semi-equilibrium dialysis

Micellar enhanced ultra-filtration (MEUF) is a modified ultrafiltration (UF) method that can remove small molecules that are not effectively removed by UF alone. In this work we used a similar semi-equilibrium dialysis (SED) method to characterize two anionic surfactants, sodium dodecyl sulfate (SDS) and sodium laurate (SOL), as MEUF candidates to remove several polycyclic aromatic hydrocarbon (PAH) compounds. These anionic surfactants have low toxicity and are more biodegradable compared to the fairly toxic and persistent cetyltrimethylammonium bromide (CTABr) and similar cationic surfactants, which is important as MEUF surfactants may be present in the treated effluent. The log binding constants (Log K_B) of the PAHs naphthalene, phenanthrene, pyrene and fluorene to SDS ranged from 3.07 to 4.48, which compared well with the previous results for CTABr and indicated that SDS is an excellent candidate for MEUF. The log binding constants for the same PAHs with SOL micelles ranged from 2.11 to 3.53, which suggested that SOL might be adequate for stronger-binding PAH like pyrene and fluorene but less suitable for naphthalene and phenanthrene. The results demonstrated a strong correlation between the Log K_B with one micelle type and the Log K_B with the other, suggesting a common set of properties and interactions are responsible for the binding. Similar to the previous results for CTABr, a significant correlation between Log K_B and Log K_OW values indicates that hydrophobic character is the main driving force for PAH binding with these anionic micelles. This may also be useful for predicting MEUF performance for various compound/surfactant combinations where Log K_B is not known.

Micellar-Enhanced Ultrafiltration Using a Plant-Derived Surfactant for Dye Separation in Wastewater Treatment

Micellar-enhanced ultrafiltration (MEUF) is one of several membrane methods used for the removal of trace organic pollutants from aqueous streams. In this process, a surfactant is added to a polluted aqueous solution at a concentration higher than its critical micelle concentration (CMC). Unlike synthetic surfactants, natural surfactants, from plants such as the saponin, while ecologically adaptable as surfactants in MEUF systems, are also biodegradable, renewable, and environmentally safe. This study applied Sapindus rarak extract as the natural surfactant in MEUF for Remazol dye separation. It was found that the presence of Sapindus rarak extract increased separation of Remazol red and blue dyes by up to 97.02% and 99.42%, respectively. However, the addition of surfactant decreased permeate fluxes due to membrane fouling and concentration polarization. In addition, loading micelle (Lm), representing the performance of the surfactant micelle for dye separation, as well as the blocking mechanism, was investigated. Lm was found to be in the range of 0.002-0.068 mM dyes/mM saponin. Ultrafiltration blocking mechanisms, as confirmed by the Hermia model, were: standard blocking, for cases without the addition of surfactant; cake formation, for cases with surfactant below the CMC; and complete blocking, for cases with surfactant above the CMC.

Role of concentration polarization in cross flow micellar enhanced ultrafiltration of cadmium with low surfactant concentration

Concentration polarization is an important issue in micellar enhanced ultrafiltration (MEUF) of wastewater containing heavy metal ions at low surfactant concentrations. In this paper, we studied removal of Cd(Ⅱ) by cross flow MEUF at low sodium dodecyl sulfate (SDS) concentration levels, and the role of concentration polarization in flux decline and Cd(Ⅱ) rejection was emphasized. Concentration polarization resistance and SDS concentration near membrane were calculated to characterize concentration polarization. The results showed that SDS concentration near membrane was 13 mM when feed concentration was merely 0.8 mM. By combining phase diagram of SDS, structures of SDS micelles in concentration polarization layer were deduced and thin layer structure transformed to porous structure formed by accumulated globular micelles when SDS concentration increased. Although micelles formed in concentration polarization layer was responsible for flux decline, they also provided adsorption sites for Cd(Ⅱ).

In-situ activated nanoparticle as an efficient and recyclable foam stabilizer for enhancing foam separation of LAS

Linear alkylbenzene sulfonate (LAS) is a particular member of the emerging contaminants, because of its increasingly ubiquitous use and tremendous harm to the environment and wastewater treatment plant. Herein, we develop a novel two-stage foam separation to recover LAS (18.7-91.0 mg/L) from laundry wastewater. We first reported the fabrication of activated silica nanoparticle (SNP) via a facile and scalable in-situ approach. To obtain a desirable surface property, the key design element was the utilization of amphoteric surfactant, viz. cocamidopropyl betaine, as the modifier. In the first-stage, activated SNP could serve as an efficient foam stabilizer to improve the foam stability and the interfacial adsorption of LAS. Remarkably, LAS concentration in effluent decreased to very low levels of 1.9-2.9 mg/L with a proper enrichment ratio, and met the emission standard. In the second-stage, we originally adopted the intensification of liquid drainage to selectively recycle activated SNP from LAS. An inclined foam channel (IFC) covered by hydrophobic coating was constructed and the maximum recovery percentage of SNP reached 91.5%, indicating that the activated SNP was recyclable. This work definitely proves that the integration of nanotechnology in foam separation can make wastewater treatment more efficient and less expensive.

Cetylpyridinium bromide assisted micellar-enhanced ultrafiltration for treating enrofloxacin-laden water

The presence of a fluoroquinolone base veterinary antibacterial drug enrofloxacin in aqueous media poses a major threat due to its ecotoxicity on aquatic microbiota. Hence, for the first time, an attempt was made to remove enrofloxacin (ENX) from its aqueous solution by employing micellar-enhanced ultrafiltration (MEUF) where cetylpyridinium bromide (CPB), a cationic surfactant was used for micellization. Response surface methodology (RSM) with central composite design (CCD) approach was applied to design the experiment, and to optimize the process parameters, namely, ENX concentration (3-15 mg/L), transmembrane pressure (2-6 kg_f/cm²), recirculation flow rate (5.5-7.5 L/min) and CPB concentration (1.4-4.2 mM). The objective of this study was to maximize the permeate flux and rejection coefficient and to find out the optimal process condition for the removal of enrofloxacin from aqueous solution. Though maximum 68.23 L/m² h of permeate flux and 94.20% of rejection coefficient were achieved at different process conditions, the optimization study reveals that the predicted optimal values of permeate flux and rejection coefficient are 67.53 L/m² h and 89.67% respectively. Modelling was also carried out with the aid of artificial neural network (ANN) to validate the prediction of RSM. The predictability of the model by RSM and ANN was compared statistically by evaluating root-mean-square error (RMSE), absolute average deviation (AAD) and mean absolute error (MAE), where ANN exhibited better predictability. The following set of parameters was proposed for industrial scale up: ENX concentration of 8.4 mg/L, TMP of 5 kg_f/cm², recirculation flow rate of 6 L/min and CPB concentration of 2.1 mM.

Roles of surfactants in pressure-driven membrane separation processes: a review

Surfactants widely exist in various kinds of wastewaters which could be treated by pressure-driven membrane separation (PDMS) techniques. Due to the special characteristics of surfactants, they may affect the performance of membrane filtration. Over the last two decades, there are a number of studies on treating wastewaters containing surfactants by PDMS. The current paper gives a review of the roles of surfactants in PDMS processes. The effects of surfactants on membrane performance were discussed via two aspects: influence of surfactants on membrane fouling and enhanced removal of pollutants by surfactants. The characteristics of surfactants in solution and at solid-liquid interface were summarized. Surfactants in membrane filtration processes cause membrane fouling mainly through adsorption, concentration polarization, pore blocking, and cake formation, and fouling degree may be influenced by various factors (feed water composition, membrane properties, and operation conditions). Furthermore, surfactants may also have a positive effect on membrane performance. Enhanced removal of various kinds of pollutants by PDMS in the presence of surfactants has been summarized, and the removal mechanism has been revealed. Based on the current reports, further studies on membrane fouling caused by surfactants and enhanced removal of pollutants by surfactant-aided membrane filtration were also proposed.

The role of surfactants in wastewater treatment: Impact, removal and future techniques: A critical review

Wastewater treatment has an important responsibility to react to changing consumer and industrial produced wastes that pose environmental challenges. Surfactants are one of these emerging contaminants. They are of interest because of their increasingly ubiquitous domestic and industrial use and the difficulty their presence causes traditional treatment. In response to this developing area, this critical review considers research from a variety of technical backgrounds to provide an up to date overview of the impact of surfactants on the environment, health and their removal. This found major concerns about surfactants on the environment and on health being corroborated in the past five years. Current research into removal focuses on existing biological and chemical wastewater treatment optimisation. Despite improvements being found to traditional biological methods using chemical pre-treatments there is a clear lack of consensus regarding the ideal strategy. Drawbacks and potential solutions for a range of these technologies, including Fenton reaction and aerobic degradation, are discussed. In this field the authors recommend an improved diversity in surfactants used for the research and addressing of significant knowledge gaps. Novel methods, such as Carbon Nanotube (CNT) use are also discussed. These methods, while showing promising results, will require continual research effort to resolve present issues such as variable performance and environmental concerns. Larger scale work is also needed to validate the initial work done. Potential uses of surfactants to optimise wastewater treatment, such as Surfactant Modified Zeolites (SMZs), are also discussed. This review finds that surfactant removal from wastewater is a promising and challenging field that warrants further investigation.

Application of saponin biosurfactant and its recovery in the MEUF process for removal of methyl violet from wastewater

The potential of saponin, a biosurfactant, in the micellar enhanced ultrafiltration (MEUF) process was tested systematically for removal of methyl violet from wastewater. For this, the aqueous extract of reetha (Sapindus mukorossi) pericarp which contains saponin was used as the biosurfactant. First, the micellar solubilization of methyl violet in saponin micelles was investigated in terms of molar solubilization power (SP) of saponin. It was observed that the adsorption of methyl violet on the agglomerates of saponin micelles was mainly responsible for the enhanced solubilization. The Gibbs free energy of solubilization (calculated as -29.63 kJ mol^-1) suggested that process was feasible and spontaneous. The MEUF experiments were performed in batch as well as continuous mode using saponin biosurfactant, and the effect of operating parameters on permeate flux and solute retention were evaluated. The removal of methyl violet in MEUF process was >99% achieved with 10 kDa polyethersulfone (PES) membrane for feed dye concentration of 250 mg L^-1 at studied conditions. Finally, the saponin in permeate was recovered using n-heptane and n-butanol by solvent extraction process. The solvent n-butanol showed better extraction efficiency as compared to n-heptane for saponin extraction.

Exploiting extracellular polymeric substances (EPS) controlling strategies for performance enhancement of biological wastewater treatments: An overview

Extracellular polymeric substances (EPS) are present both outside of the cells and in the interior of microbial aggregates, and account for a main component in microbial aggregates. EPS can influence the properties and functions of microbial aggregates in biological wastewater treatment systems, and specifically EPS are involved in biofilm formation and stability, sludge behaviors as well as sequencing batch reactors (SBRs) granulation whereas they are also responsible for membrane fouling in membrane bioreactors (MBRs). EPS exhibit dual roles in biological wastewater treatments, and hence the control of available EPS can be expected to lead to changes in microbial aggregate properties, thereby improving system performance. In this review, current updated knowledge with regard to EPS basics including their formation mechanisms, important properties, key component functions as well as sub-fraction differentiation is given. EPS roles in biological wastewater treatments are also briefly summarized. Special emphasis is laid on EPS controlling strategies which would have the great potential in promoting microbial aggregates performance and in alleviating membrane fouling, including limitation strategies (inhibition of quorum sensing (QS) systems, regulation of environmental conditions, enzymatic degradation of key components, energy uncoupling etc.) and elevation strategies (enhancement of QS systems, addition of exogenous agents etc.). Those strategies have been confirmed to be feasible and promising to enhance system performance, and they would be a research niche that deserves further study.

Anion Exchange on Cationic Surfactant Micelles, and a Speciation Model for Estimating Anion Removal on Micelles during Ultrafiltration of Water

Surfactant micelles combined with ultrafiltration can partially, or sometimes nearly completely, separate various ionic and nonionic pollutants from water. To this end, the selectivity of aqueous micelles composed of either cetyltrimethylammonium (CTA⁺) bromide or cetylpyridinium (CP⁺) chloride toward many environmentally relevant anions (IO₃^-, F^-, Cl^-, HCO₃^-, NO₂^-, Br^-, NO₃^-, H₂PO₄^-, HPO₄^2-, SO₄^2-, and CrO₄^2-) was investigated. Selectivity coefficients of CTA⁺ micelles (with respect to Br^-) and CP⁺ micelle (with respect to Cl^-) for these anions were evaluated using a simple thermodynamic ion exchange model. The sequence of anion affinity for the CTA⁺ micelles and for the CP⁺ micelles were the same, with decreasing affinity occurring in the order of: CrO₄^2- > SO₄^2- > HPO₄^2- > NO₃^- > Br^- > NO₂^- > Cl^- > HCO₃^- > H₂PO₄^- ≈ F^-. From the associated component mass balance and ion exchange (i.e., mass action) equations, an overall speciation model was developed to predict the distribution of all anions between the aqueous and micellar pseudophase for complex ionic mixtures. Experimental results of both artificial and real surface waters were in good agreement to model predictions. Further, the results indicated that micelles combined with ultrafiltration may be a potential technology for nutrient and other pollutant removal from natural or effluent waters.