Diallyldimethyl Ammonium Research Articles

Removal of Methylene Blue Dye from Aqueous Solution using PDADMAC Modified ZSM-5 Zeolite as a Novel Adsorbent

In the present work, we modified ZSM-5 zeolite using a bio polymer poly (diallyl dimethyl ammonium chloride) and employed it for the removal of cationic dye, methylene blue from aqueous solution. The chemical and physical properties of the modified ZSM-5 zeolite were investigated using XRD, FTIR, SEM, TEM, nitrogen adsorption, TGA and 27Al NMR. Modified ZSM-5 zeolite possesses high surface area and pore diameter which was confirmed from SEM, TEM and nitrogen adsorption analysis. Adsorption of methylene blue on zeolite was investigated by batch adsorption technique. The effect of different parameters such as zeolite dosage, initial methylene blue concentration, temperature, pH and contact time on the adsorption process was discussed. Maximum adsorption capacity (4.31 mg/g) was achieved using 0.1 g of modified ZSM-5 zeolite at the optimum conditions (initial dye concentration: 10 mg/L, pH 10, temperature: 30 °C and contact time: 300 min). The experimental data were fitted into Langmuir and Freundlich models and the results indicate that the adsorption process followed Freundlich isotherm. Kinetic data were investigated using pseudo-first-order and pseudo-second-order models. Kinetic analysis indicates that pseudo-second-order model is more suitable to describe adsorption of MB on modified ZSM-5 zeolite. The reusability test suggests that the adsorbent could be reused at least six times without significant loss in removal efficiency.

In-fiber optofluidic online SERS detection of trace uremia toxin.

In this Letter, we propose a microstructured in-fiber optofluidic surface-enhanced Raman spectroscopy (SERS) sensor for the initial inspection of uremia through the detection of unlabeled urea and creatinine. As a natural microfluidic device, microstructured hollow fiber has a special structure inside. Through chemical bonds, the SERS substrate can be modified and grown on the surface of the suspended core. Here, the silver nanoparticles (Ag NPs) are embedded on the poly diallyl dimethyl ammonium chloride-modified graphene oxide sheet to achieve the self-assembled SERS substrate. The reduced distance between Ag NPs can increase the strong hot spots that generate enhanced Raman signals. Therefore, it can effectively detect the Raman signal of unlabeled trace uremic toxin analytes (urea, creatinine) inside the optical fiber. The results show that under simulated biophysical conditions, the limit detection (LOD) for urea is 10-4M and the linearity is good, especially at the clinical conventional concentration range (2.5-6.5×10-3M). In addition, the online Raman detection of creatinine aqueous solution LOD is 10-6M, which also has good linearity. Significantly, this Letter provides a microstructured optofluidic in-fiber Raman sensor for the preliminary detection of uremia, which will have good development prospects in the field of clinical biomedicine.

Polycationic Polymer Layer for Air-Stable and Dendrite-Free Li Metal Anodes in Carbonate Electrolytes.

The short cycle life and safety concerns caused by uncontrollable dendrite growth have severely hindered the commercialization of lithium metal batteries. Here, a polycationic and hydrophobic polymer protective layer fabricated by a scalable tape-casting method is developed to enable air-stable, dendrite-free, and highly efficient Li metal anodes. The polymeric cations of poly(diallyl dimethyl ammonium) (PDDA) provide an electrostatic shielding effect that unifies Li+ flux at the surface of the Li anode and promotes a homogeneous Li plating, while the bis(trifluoromethanesulfonyl)imide (TFSI) anions bring hydrophobic characteristics and improve moisture stability. The accumulated TFSI anions by the polycationic film also facilitate the formation of a stable solid electrolyte interphase (SEI). Steady Li plating/stripping in the carbonate electrolyte can be achieved under a high areal capacity of 10 mAh cm-2 for 700 h with Li utilization efficiency up to 51.6%. LiNi0.8 Mn0.1 Co0.1 O2 and LiFePO4 cells using the modified anode exhibit much improved electrochemical performance compared with the bare Li counterpart. Moreover, ultrasonic imaging shows no gas generation in the modified Li/LiFePO4 pouch cell. Mechanism investigation demonstrates the stable SEI and homogeneous Li deposition derived by the polycationic layer.

Surface Plasmon Resonance Field-Enhanced Fluorescence Properties of Gold Quantum Dots on Polyelectrolyte Multilayers and Their H2O2 Sensor Application

In this work, we investigate surface plasmon field-enhanced fluorescence (SPF) emission from gold quantum dots (AuQDs) on a polyelectrolyte multilayer ultrathin film deposited onto an Al thin film. Polyelectrolyte layers of poly(diallyl dimethyl ammonium chloride) (PDADMAC) and poly(sodium 4-styrenesulfonate) (PSS) are deposited onto the Al surface using a layer-by-layer (LbL) adsorption technique. AuQDs are subsequently deposited onto the PDADMAC/PSS ultrathin films to study their fluorescence enhancement/quenching phenomenon, as monitored by SPF spectroscopy. The distance between the AuQDs and the Al thin film is controlled by the number of deposited PDADMAC/PSS LbL films. With increasing number of the PDADMAC/PSS bilayers, the fluorescence intensity of the AuQDs increases until the optimum distance between the AuQDs and Al layers is achieved. Moreover, silver nanoprisms (AgNPrs) are coated onto the AuQDs for H2O2 sensing. When the AgNPrs are present, a decrease in the fluorescence intensity of the AuQDs due to energy transfer from the AuQDs to the AgNPrs is observed. Recovery of the fluorescence intensity of the AuQDs is observed upon injection of a H2O2 solution, where the recovery of the intensity is proportional to the H2O2 concentration in the range from 1 pM to 100 nM and results from the oxidation reaction or etching of the AgNPrs. The fluorescence recovery is attributed to weakening of the quenching effect by a reduction in concentration of the AgNPrs. The proposed system exhibits strong potential for the development of H2O2 sensors.

Graphene‐Oriented Construction of 2D SnS for Methanol Gas‐Sensor Application

Group‐IV monochalcogenides with unique 2D puckered honeycomb structure (MX, M = Ge, Sn/X = S, Se) have a great prospect in the gas‐sensor field. Herein, an exploratory study on 2D SnS is synthesized through a solvothermal method, is performed for promising methanol sensor. To break through the inhibition of the general agglomeration and poor conductivity of solvothermal synthesized SnS on gas‐sensing performance, a hybrid of SnS@rGO is designed and constructed based on poly(diallyl dimethyl ammonium chloride) (PDDA)‐assisted electrostatic self‐assembly. With directed growth of SnS on the PDDA‐modulated graphene oxide (GO), an expected architecture characterized by well‐dispersed loosely arranged SnS nanosheets attaching on the highly conductive rGO is achieved. The unique hybrid architecture and the conductivity modulation of rGO promotes sensing responses and dynamic characteristic of SnS‐based sensor toward methanol detection. The achieved SnS@rGO hybrid with less stacking architecture of SnS displays a ≈3.3‐fold enhancement in gas response to 15 ppm methanol in comparison to the flower‐like stacked SnS. The formation mechanism of SnS@rGO hybrid based on the oriented growth of SnS by PDDA‐modulated GO is clarified schematically and the response enhancement of the hybrid is demonstrated in terms of the unique architecture and the conductivity modulation.

Sulfur@Self-assembly 3D MXene hybrid cathode material for lithium-sulfur batteries

High energy density Lithium-Sulfur (Li-S) batteries have attracted significant attention, although their severe energy decay and rate capability loss still hinder their large-scale application. Two-dimensional (2D) MXene materials can immobilize polysulfides via strong chemisorption and physical hinderance. However, MXene nanosheets tend to restack in solution, losing their favorable electronic conductivity due to functional substituents on the surface. In this work, a three-dimensional (3D) MXene material is fabricated with MXene nanosheets and carbon-poly (diallyl dimethyl ammonium chloride) nanoparticles using self-assembly strategy. As the sulfur host, the 3D material not only prevents MXene nanosheets from restacking, but also ensures to provide a framework to confine S and raises the utilization of sulfur. As a result, the sulfur cathode demonstrates a highly reversible specific capacity of 1016.8 mAh g−1 at 0.2 C, excellent rate capability, and long-term cycling stability, with the capacity decay rate of only 0.075% per cycle over 600 cycles at 1 C.

Pre-coagulation with cationic flocculant-composited titanium xerogel coagulant for alleviating subsequent ultrafiltration membrane fouling by algae-related pollutants

In-line coagulation-ultrafiltration is reliable to achieve the safe disposal of algae-laden water with alleviated membrane fouling. Poly(diallyl dimethyl ammonium chloride) (PDADMAC)-composited titanium xerogel (TXC) coagulant (abbreviated as P-T) was reported to possess better resistance to organic matter loads, and its mitigation effect on subsequent ultrafiltration efficiency towards algae-related pollutants was investigated in this study. Results showed that P-T coagulation effectively mitigated membrane fouling over pH 5.0–9.0, whereas TXC only worked better under acidic condition. Acidic environment facilitated algae and organic matter removal by pre-coagulation, thus greatly improving ultrafiltration efficiency. Under neutral and alkaline conditions, PDADMAC portion in P-T enhanced the coagulation removal towards algae and protein constituents, and simultaneously promoted the formation of flocs with unique porous structure, which jointly contributed to its high-efficient alleviation ability. Nevertheless, PDADMAC increased adhesion force between P-T coagulated flocs and membrane surface, thus slightly reducing the recovery rate of membrane flux at pH 5.0. Pearson correlation analyses implied that removing algae cells would prevent reversible fouling-induced flux decline, whereas eliminating organic matter could greatly promote ultrafiltration efficiency via mitigating irreversible fouling. Therefore, elevating removal efficiency of organic matters is still the major objective for ultrafiltration pretreatment technologies and the optimization direction towards TXC-based coagulants.

Dye-sensitized solar cells based on MK2 dye, PMMA-based quasi-solid electrolyte, and flexible CNT counter electrode

In this paper, a dye-sensitized solar cell based on organic MK2 dye, a quasi-solid electrolyte, and a flexible counter electrode was investigated. Two types of TiO2 nanoparticles with different sizes were used to make the photoanode with a bi-layer structure. The quasi-solid electrolyte was made based on polymethylmethacrylate (PMMA) and iodide/triiodide couple. The counter electrode was fabricated by electrophoresis deposition of carbon nanotube (CNT) mixed with diallyl dimethylammonium chloride (PDDA) on a flexible stainless-steel mesh. A cellulose separator was used to improve the stability of the solar cell. A simple and low-cost sealing method using polypropylene-based tape has been proposed and used for conducting the stability test. The maximum conversion efficiency of 2.5% (under simulated AM 1.5) was obtained with the fabricated quasi-solid dye-sensitized solar cells.

Pd nanoparticles assembled on Ni- and N-doped carbon nanotubes towards superior electrochemical activity

Metal-based catalysts within single-atom to 1–2 nm size range are attracting considerable attention recent years. Carbon-based materials with their excellent electro- and photo-chemical properties are ideal candidates as supporting substrate for constructing of metal catalyst. Here we report a palladium (less than 5 nm in average diameter) deposited Ni carbon nanotubes (CNTs) with Ni metal nanoparticles (NPs) to be around single atom to 1–2 nm on average. Mono-dispersed Pd NPs are homogeneously immobilized on both synthesized Ni- and N-doped CNTs and N-doped commercial made CNTs using poly(diallyldimethyl ammonium) chloride (PDDA) as the key bonding components. Enhanced electrocatalytic activity is observed in measurements including hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and methanol oxidation reaction (MOR), with some of the samples having higher HER (under acidic condition) and OER (under basic condition) activity comparing with the commercial Pd/C (40 wt%) sample. The result provides a forward-looking strategy for fabricating efficient and low-cost catalysts.

Antibacterial Effect of Silver Nanoparticles on Klebsiella spp

Silver nanoparticles (AgNP) can be incorporated into medical devices, such as tissues, to circumvent bacterial resistance such as Klebsiella spp, which can lead to skin and mucosal infections. Thus, the aim of the present study was to synthesize silver nanoparticles for later incorporation into cotton fabrics and in vitro tests against Klebsiella spp. The AgNP colloidal solution was synthesized (AgNO3 - 0.1 mM, 100 mM trisodium citrate, polyvinylpyrrolidone - 0.24 g, H2OH2) and then impregnated into the cotton fabric pretreated with poly diallyl dimethylammonium chloride (PDDA) of 100/500 tissue, shaken for 30 minutes). The material produced was analyzed by the FTIR; DLS and reflectance spectroscopy. The tests of the antimicrobial activities were by the microdilution technique against Klebsiella spp, in tubes containing Brain Heart Infusion (BHI), with the solution of silver (1); Tissue containing AgNP - 4 mm (2); Negative control (3) and positive control - ceftriaxone (4). Regarding MIC, the inhibitory activity occurred of the dilutions between 1/2 and 1/16. The AgNP particles had an average size of 24.75 nm. As synthesized AgNPs demonstrate the excellent antimicrobial activity against Klebsiella spp, with special emphasis on applications in nanotechnology and nanomedicine, targeting multiresistant antibiotic bacteria.

Hydrophobic polymer-incorporated hybrid 1D photonic crystals with brilliant structural colors via aqueous-based layer-by-layer dip-coating

Preparation and application of photonic crystal (PC) films with structural colors have received extensive attention in recent years. Aqueous-based layer-by-layer (LbL) dip-coating is an environmentally friendly and versatile method to prepare functional films. This work focuses on using the method to prepare a kind of hydrophobic polymer-containing 1D PCs with brilliant structural colors. High and low refractive index stacks are produced by electrostatic assembly of nano TiO2/poly (styrene sulfonate) (PSS) and poly (diallyldimethyl ammonium chloride) (PDAC)/nano poly (methyl methacrylate) (PMMA) multilayers, respectively. Hydrophobic PMMA was introduced for the first time in this aqueous-based electrostatically-assisted assembly for expanding the applicable materials. The zeta potential and particle size of the PMMA and TiO2 nanoparticles are measured under different pHs, and the effects of the bilayer number on both film thickness and refractive index are investigated. The structural colors of the heterostructure 1D PCs can be regulated in the visible range by variation of bilayer number, incident angle and stack number. This hydrophobic polymer incorporated 1D PCs can achieve colorful coatings on flat and curved glass substrates. In addition, upon exposure to organic solvent vapors, the PC film shows color change. Thereby, the obtained multilayered PCs exhibit potential applications in coating, decoration and sensing.

Preparation of natural rubber based semi-IPNs superabsorbent and its adsorption behavior for ammonium

In this study, a natural rubber (NR) based amphiphilic semi-interpenetrating polymer network (semi-IPN) superabsorbent hydrogel was designed and synthesized with natural rubber-graft-poly (acrylic acid-co-acrylamide) [NR-g-P(AA-co-AM)] network and linear poly (diallyldimethyl ammonium chloride) (PDADMAC). Through a series of characterization and test, the structure, morphology, thermal properties, biodegradation, and swelling properties of NR-g-P(AA-co-AM)/PDADMAC were determined. Subsequently, NR-g-P(AA-co-AM)/PDADMAC was used for ammonium adsorption to remove ammonium nitrogen in aqueous solution. The adsorption behavior of the absorbent was also studied. Results showed that the maximum water absorbency of NR-g-P(AA-co-AM)/PDADMAC was 112.04 ± 6.55 g/g and water retention capacity of soil with the superabsorbent was 115.62 ± 2.08%. The NH4+ adsorption quickly reached equilibrium and the maximum adsorption capacity was 13.02 mmol g−1 calculated from Langmuir isotherm model. The results suggest that the product is efficient for ammonium removal and can be used as water-retaining agents.

Synthesis of Diallyl dimethyl ammonium chloride grafted polyvinyl pyrrolidone (PVP-g-DADMAC) and its applications

The search for a sustainable and nontoxic polymeric product has fired an intense research in the field of graft copolymers. This study endeavor to create a polyacrylamide free novel flocculant which showed efficient behavior towards water and wastewater treatment and for mineral ore beneficiation. We synthesized the novel graft copolymer - Poly Diallyl Dimethyl Ammonium Chloride (DADMAC) grafted polyvinyl pyrrolidone (PVP-g-pDADMAC) via graft polymerization route by microwave assisted method. The synthesized novel cationic graft co-polymer has been characterized by elemental analysis, FTIR spectroscopy, intrinsic viscosity measurement, molecular weight determination, and scanning electron micrograph (SEM), taking PVP as reference. The effects of reaction parameters onto the percentage grafting have been studied. The applicability of these grafted polymers as flocculant for the treatment of municipal sewage waste water as well as for mineral ore beneficiation and for suppression of nanopollutant like multi-walled carbon Nano-tubes (MWCNTs) (as nano scavenger) from water systems were also investigated.

Counterion exchanged hydrophobic polyelectrolyte multilayer membrane for organic solvent nanofiltration

Organic solvent nanofiltration is a promising separation technology for removing solute from an organic medium. However, the fabrication of organic solvent nanofiltration membranes with stable separation performance is still a challenge. Herein, a hydrophobic polyelectrolyte multilayer membrane was prepared through a layer-by-layer self-assembly and counterion exchange method. Poly(diallyl dimethyl ammonium chloride) (PDDA)/polyacrylic acid (PAA) multilayer was self-assembled on the surface of the hydrolyzed polyacrylonitrile substrate through electrostatic interaction. Simultaneously, calcium silicate hydrate (CSH) nanoparticles were in situ grown during the multilayer formation process due to the incorporation of precursor in polyelectrolyte solutions. Therefore, the surface roughness of the membrane was enhanced and the anti-swelling property of the polyelectrolyte multilayer was also improved. The hydrophilic [(PDDA/PAA-CSH)2.5]+Cl− membrane was then converted to the hydrophobic membrane through the counterion exchange between Cl− and perfluorooctanate (PFO−) ions. The obtained [(PDDA/PAA-CSH)2.5]+PFO− membrane has a water contact angle of 118°, which can be used to separate dyes from ethanol. Both the separation performance and stability of the polyelectrolyte multilayer membrane were improved through the in situ growth of calcium silicate hydrate nanoparticles and counterion exchange by perfluorooctanate ions. Therefore, this strategy may open a new avenue to prepare organic solvent nanofiltration membranes.

Highly Sensitive and Selective Colorimetric Sensor of Mercury (II) based on Layer-by-Layer Deposition of Gold/Silver Bimetallic Nanoparticles.

A new colorimetric sensor based on gold/silver bimetallic nanoparticles (Au–Ag BNPs) for the sensitive and selective detection of mercury (II) was developed. Gold nanoparticles (AuNPs) were synthesized by Turkevich method. The surface modification of AuNPs was modified by the layer–by–layer technique using poly(diallyl dimethylammonium chloride) which provided positively charged of AuNPs. Negatively charged silver nanoparticles (AgNPs) were synthesized by chemical reduction using poly(4–styrenesulfonic acid–co–maleic acid) as the stabilizing agent. The layer–by–layer assembly deposition technique was used to prepare Au–Ag BNPs of positively and negatively charged of AuNPs and AgNPs, respectively. The synthesized Au–Ag BNPs were characterized by a UV-visible spectrophotometer, zeta potential analyzer, FT–IR, TEM, XRD, and EDX. The Au–Ag BNPs sensor was able to detect mercury (II) in aqueous solution, visibly changing from brownish–orange to purple. The linear relationships of the UV-visible spectrometry demonstrate that the Au–Ag BNPs-based colorimetric sensor can be used for the quantitative analysis of mercury (II) in the range of 0.5–80 mg L−1, with the correlation coefficient, r2 = 0.9818. The limit of detection (LOD) of mercury (II) was found to be 0.526 + 0.001 mg L−1. The BNPs is also verified to have a good practical applicability for mercury (II) detection in the real samples.

Synthesis and characterization of a novel cationic polyacrylamide-based flocculants to remove Congo red efficiently in acid aqueous environment

Dye treatments in industrial wastewaters causes numerous obstacles while stains exist normally constant to radiance as well as corrosion and thus, aerobic digestion. The removal of Congo red dye in low concentration from acidic aqueous solution is the main objective of present work. Synthesis of Acrylamide (AM), Diallyl Dimethyl Ammonium Chloride Propylene (DADMAC) and Acryloyloxyethyltrimethyl ammonium chloride (DAC) (PADD) were carried by UV-initiated polymerization, and polyacrylamide (PAM) as contrast sample. Several analytical techniques existed employed to characterization and demonstrate the productive synthesize of PADD, characteristics and composition of the flocculants was studied through FTIR, 1HNMR while thermal stability of PADD in addition PAM was studied by TGA. In addition, the strong structure of surface morphology was confirmed by scanning electronic microscopy (SEM). Established effective process was used to evaluate the flocculation behaviour with special characteristics. Measuring the parameters, dosage of flocculants, flocculation time, temperature, flocculants initial concentration of Congo red dye, stirring speed and zeta potential in removal of Congo red efficiently in acid aqueous environment. These factors presented that in the condition of strong acidity, low concentration and charge neutralization, the adsorption and bridging effect of PADD on Congo red dye was dominant. Under the idyllic conditions concentration of dye 3.0 mg L−1 and pH 6.0, the maximum removal rates of Congo red dye have been 96.45% and 81.10%, PADD and PAM, respectively. PADD provides a scientific basis platform for the removal of Congo red dye efficiently.

Layer-by-layer self-assembled covalent triazine framework/electrical conductive polymer functional separator for Li-S battery

Lithium-sulfur (Li-S) battery is attracting intense attention due to its extremely high theoretical specific capacity and low cost. However, the dissolution and diffusion of lithium polysulfides (LiPS), as well as the insulating property of sulfur and its discharge products, limit the practical application of Li-S battery. In this work, we developed an ultralight functional separator (LBL-fseparator) with orderly structure and multifunctional properties through electrostatic layer-by-layer (LBL) self-assembly of positively charged poly(diallyl dimethyl ammonium chloride) (PDDA) wrapped covalent triazine framework (CTF) (CTF@PDDA) and negatively charged poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT: PSS) to effectively retard LiPS shuttle and improve the utilization of active sulfur material. The CTF@PDDA as LiPS shuttle inhibiting layers displays strong LiPS-anchor ability through physical/chemical interaction as well as excellent electrolyte uptake capacity due to its large specific surface area and porous structure, while the PEDOT: PSS as the conductive layers improves electron transfer as well as excellent interface stabilizer and adhesion binder. It was demonstrated that the proposed LBL-fseparator assembled with general S-cathode and Li metal anode displays commendable cycling stability (0.052% capacity fade-rate per cycle over 1000 cycles at 1C), superb utilization of sulfur (90.7% at 0.1C and 59.2% at 2C), and enhanced protection ability of the Li metal. The excellent battery performance and easily mass-produced method provide a useful strategy for industrial-scale production.

INCLUSION AND ANTIFUNGAL ACTIVITY OF ACRYLIC RESINS INCLUDING POLY (DIALLYLDIMETHYLAMMONIUM CHLORIDE) BIOCIDE

Objective: The aim of this study was to evaluate the antifungal activity of the self-curing and thermo-polymerizable acrylic resin when we added the poly (diallyl dimethylammonium chloride; PDADMAC) biocide to these materials. Study design: The PDADMAC was diluted in tetrahydrofuran to obtain a 4% weight concentration, and it was added to the acrylic resin during the polymerization process. From this point we obtain the test bodies, and the control test bodies without PDADMAC (white). Contact angle measurements were performed with water droplets using Phoenix equipment (SEO, Korea) to verify the presence of the biocide in the acrylic resins. The sterilization of the specimens was achieved with gamma radiation, and we did the antifungal tests, G21-15 and E2149-13, with Candida albicans (ATCC 10231) and Aspergillus niger (ATCC 16404).Results: The bodies tests with PDADMAC showed lower angles of contact than the white test sample, demonstrating the inclusion of PDADMAC. Regarding antifungal tests, the G21-15 test demonstrated significant efficacy in both fungi, but the E2149-13 test was effective only against C. albicans. Conclusions: The inclusion of PDADMAC in acrylic resins was successful and determinant to achieve antifungal efficacy.

Sacrificial coating development for biofouling control in membrane systems

Current cleaning strategies for biofouling control on spiral wound membrane systems used for seawater desalination are not effective and can hinder long-term membrane performance. To enable effective cleaning of a membrane, we examined the in-situ application and the use of a sacrificial multilayer polyelectrolyte coating on the membrane surface. The membrane coating was based on a layer-by-layer assembly approach using two non-toxic linkers, poly (diallyl-dimethyl ammonium chloride) and poly(sodium-4-styrene sulfonate). This polyelectrolyte coating was effectively applied on the membrane surface under cross-flow conditions, and it was stable on the membrane surface under continuous operation. Coating removal requires only a concentrated sodium chloride solution (synthetic brine in our study) adjusted to pH 11. Using this procedure, both the biofilm and the sacrificial layer could be simultaneously removed, leaving a clean surface compared to the non-coated membrane. Biofouling tests showed that the coated membrane had two-fold higher permeate flux recovery than the control non-coated membrane. The used polyelectrolyte sacrificial coatings avoided the use of toxic linkers and harsh cleaning chemicals, and thus it is a suitable technique for biofouling control on reverse osmosis spiral wound membranes.

Cationic dye adsorption by phosphomolybdate nanoclusters immobilised on polyelectrolyte matrix

A polyelectrolyte complex (PEC) made up of poly(di-allyl di-methylammonium chloride) and poly(styrene sulphonate) polyelectrolytes has been synthesised and used for the immobilisation of phosphomolybdate (PMo), $$ \left[ {{\text{PMo}}_{12} {\text{O}}_{40} } \right]^{ 3- } $$ nanoclusters. The material is characterised by FTIR, powder XRD, SEM, TEM and UV-Visible DRS spectroscopy. It was found that the PMo clusters are intact in the hybrid and are present as nanoaggregates within the layers of PEC. The amount of PMo present in the hybrid is estimated from thermal measurements and the optical band gap energy of the material is found to be in the semiconductor region. The presence of negatively charged PMo clusters helped in almost complete adsorption of cationic dyes, methylene blue and rhodamine B. The PMo/PEC hybrid has shown to follow Langmuir adsorption isotherm in case of both the dye molecules. Polyelectrolyte complex immobilised with Keggin-type phosphomolybdate ions showing efficient adsorption of Methylene Blue and Rhodamine B dye molecules.