Synergistic effect of KI on the corrosion inhibition of a poly(diallylammonium chloride)-based cyclocopolymer containing bis-cationic motifs for mild steel corrosion in 20% formic acid.

This study entails the syntheses of a homopolymer, poly(diallylammonium chloride) (3), and copolymers (8a-c) containing hydrophilic/hydrophobic pendants and their role in mitigating mild steel in aggressive 20% formic acid, a type of corrosion that is not frequently discussed in the literature. The synthesized homopolymer and copolymers were characterized by FTIR, NMR, viscometry, and TGA. Inhibitor 8b was found to be the most potent, with 81.8% inhibition efficiency (IE) registered via the potentiodynamic polarization method for 100 ppm of inhibitor concentration at 30 °C. Inhibitor 8b, mixed with 2 mmol KI, showed more than 90% IE for a meager 1 ppm inhibitor concentration. For a synergism of 50 ppm inhibitor and 2 mmol KI, the IE reached a high value of 99.1%. The synergism was so good that it helped the inhibitor retain ∼100% of its original IE even after a 24 h weight loss study at 60 °C. The adsorption isotherm study showed that 8b followed the Langmuir adsorption isotherm and adsorbed via chemisorption. A very high value (2.48 × 105 L mol-1) of the equilibrium adsorption constant (Kads) indicated strong adsorption. XPS and SEM surface studies provided evidence of the inhibitor found on the metal surface. Some toxicological parameters, such as LC50, bioaccumulation factor, and developmental toxicity, have been measured computationally. A brief mechanistic insight into how the inhibitors functioned has been offered along with the DFT study.

Fabrication of a New Rationally Designed Mussel-Inspired Cationic Amphiphilic Terpolymer to Enhance the Separation and Anti-Fouling Performance of Membranes.

Polyvinylidene fluoride (PVDF) membrane-based systems for treating oily wastewater are prone to fouling. Herein, we introduced a novel mussel-inspired cationic amphiphilic terpolymer consisting of monomers N,N-diallyldimethylammonium chloride (DADMAC), N,N-diallyltetradecan-1-ammonium chloride (DTDAC), and mussel-inspired N,N-diallyldopamine hydrochloride (DADAHC) to improve the performance and characteristics of the PVDF membranes for oil-in-water emulsion separations. The cationic terpolymer, poly(DADMAC-co-DTDAC-co-DADAHC), shortened as PDDD, was synthesized in excellent yields via free radical polymerization and has good compatibility with the PVDF owing to the presence of hydrophobic long alkyl chains in DTDAC. The presence of dopamine motifs helps stabilize the PDDD-PVDF membrane by chelating with Fe3+ ions. The water contact angle on the PDDD-incorporated PVDF membranes was reduced from 87.6 to 54.6°, demonstrating improved hydrophilicity than pristine PVDF (M-0). The incorporation of PDDD into the PVDF improved the separation efficiencies of the membrane, which reached up to 99% while treating the oil-in-water emulsions. Incorporating PDDD into PVDF has significantly enhanced the anti-fouling characteristics of the membranes, which are indicated by their remarkable flux recovery ratio (FRR) (up to 92%). The hydrophobic and hydrophilic groups worked synergetically to enhance the performance of the fabricated membrane.

Stimuli-Responsive Macromolecular Architecture by Butler Cyclopolymerizations: Synthesis and Applications.

This article reviews the synthesis of polyzwitterions (PZs) (poly-carboxybetaines, -phosphonobetaines, and -sulfobetaines) having multiple pH-responsive centers. The synthesis follows the Butler cyclopolymerization protocol involving a multitude of diallylammonium salts and their copolymerization with SO2 and maleic acid. The PZs have been transformed into cationic-, anionic-polyelectrolytes, and polyampholytes under the influence of pH. Particular attention is given to the application of these polymers as antiscalants, mild steel corrosion inhibitors, components in constructing Aqueous Two-Phase Systems (ATPSs), and membrane modifiers. The ATPSs could be used to separate various biomolecules, including proteins. Many amphiphilic polymers incorporating a few mol % hydrophobic monomers have shown enhanced viscosities and could be suitable for applications in oil fields. The progress of applying Butler cyclopolymerization in reversible addition-fragmentation chain transfer (RAFT) chemistry has been discussed. Future works are expected to focus on RAFT cyclopolymerization to construct block copolymers.

A sorbent containing pH-responsive chelating residues of aspartic and maleic acids for mitigation of toxic metal ions, cationic, and anionic dyes.

t-Butyl hydroperoxide-initiated cycloterpolymerization of diallylaminoaspartic acid hydrochloride [(CH2[double bond, length as m-dash]CHCH2)2NH+CH(CO2H)CH2CO2H Cl-] (I), maleic acid (HO2CH[double bond, length as m-dash]CHCO2H) (II) and cross-linker tetraallylhexane-1,6-diamine dihydrochloride [(CH2[double bond, length as m-dash]CHCH2)2NH+(CH2)6NH+ (CH2CH[double bond, length as m-dash]CH2)2 2Cl-] (III) afforded a new pH-responsive resin (IV), loaded with four CO2H and a chelating motif of NH+⋯CO2 - in each repeating unit. The removal of cationic methylene blue (MB) (3000 ppm) at pH 7.25 and Pb(ii) (200 ppm) at pH 6 by IV at 298, 313, and 328 K followed second-order kinetics with E a of 33.4 and 40.7 kJ mol-1, respectively. Both MB and Pb(ii) were removed fast, accounting for 97.7% removal of MB within 15 min at 313 K and 94% of Pb(ii) removal within 1 min. The super-adsorbent resin gave respective q max values of 2609 mg g-1 and 873 mg g-1 for MB and Pb(ii). IV was also found to trap anionic dyes; it removed 91% Eriochrome Black T (EBT) from its 50 ppm solutions at pH 2. The resin was found to be effective in reducing priority metal contaminants (like Cr, Hg, Pb) in industrial wastewater to sub-ppb levels. The synthesis of the recyclable resin can be easily scaled up from inexpensive starting materials. The resin has been found to be better than many recently reported sorbents.

Synthesis of a biomimetic zwitterionic pentapolymer to fabricate high-performance PVDF membranes for efficient separation of oil-in-water nano-emulsions.

Oily wastewater from industries has an adverse impact on the environment, human and aquatic life. Poly(vinylidene fluoride) (PVDF) membrane modified with a zwitterionic/hydrophobic pentapolymer (PP) with controlled pore size has been utilized to separate oil from water from their nano-emulsions. The PP has been synthesized in 91% yield via pentapolymerization of four different diallylamine salts [(CH2=CHCH2)2NH+(CH2)x A-], bearing CO2-, PO3H-, SO3-, (CH2)12NH2 pendants, and SO2 in a respective mol ratio of 25:36:25:14:100. Incorporating PP into PVDF has shown a substantially reduced membrane hydrophobicity; the contact angle decreased from 92.5° to 47.4°. The PP-PVDF membranes have demonstrated an excellent capability to deal with the high concentrations of nano-emulsions with a separation efficiency of greater than 97.5%. The flux recovery ratio (FRR) of PP-5 incorporated PVDF membrane was about 82%, which was substantially higher than the pristine PVDF.

A resin containing motifs of maleic acid and glycine: a super-adsorbent for adsorptive removal of basic dye pararosaniline hydrochloride and Cd(II) from water.

The cyclocopolymerization of N,N-diallylglycine hydrochloride, maleic acid and 1,1,4,4-tetraallylpiperazinium dichloride afforded a cross-linked polyzwitterionic acid, which, upon treatment with NaOH, gave the corresponding cross-linked anionic polyelectrolyte (CAPE) in quantitative yield. The pH-responsive resins contained a high density of CO2 - motifs as well as the chelating motifs of glycine residues. The resin CAPE was found to be a super-adsorbent for the removal of pararosaniline hydrochloride (PRH); having a q max of 1534 mg/g. The adsorption process followed pseudo-second-order kinetics and was found to be a nearly irreversible process as suggested by the parameters obtained from Elovich kinetic model. The resin demonstrated excellent adsorption/desorption efficiencies, thereby ensuring its recycling and reuse in potent applications like remediation of industrial dye-waste water. The resin's chelating motifs were also efficient in the adsorptive removal of Cd(II) ions with a q max of 248 mg/g. It was also employed for the simultaneous and effective trapping of Cd(II) and the dye from industrial wastewater. The resin's impressive performance accords it a prestigious place among many sorbents in recent works.

Hydroquinone Decorated with Alkyne, Quaternary Ammonium, and Hydrophobic Motifs to Mitigate Corrosion of X-60 Mild Steel in 15†wt.% HCl.

1-(6-Bromohexyloxy)-4-propargyloxybenzene upon quaternization with 3-dimethylamino-1-propanol and N,N-dimethyldodecylamine produced two new inhibitor molecules: N-[6-(4-Propargyloxyphenoxy)hexyl]-N,N-dimethyl-N-(3-hydroxypropyl)ammonium bromide (PHAB) and N-[6-(4-Propargyloxyphenoxy)hexyl]-N,N-dimethyl-N-dodecylammonium bromide (PDAB), respectively, in excellent yields. The inhibitor molecules were characterized by elemental analysis, Fourier transform infrared spectroscopy, 1 H NMR, and 13 C NMR spectroscopy. The inhibitors were evaluated for X-60 mild steel corrosion in 15 wt.% HCl using different electrochemical and gravimetric techniques. The potentiodynamic polarization confirms both the inhibitors as mixed-type corrosion inhibitors. A low concentration (15 ppm) of PDAB has demonstrated excellent corrosion inhibition efficiencies of 97%, 98%, and 86% at 25 °C, 50 °C, and 70 °C, respectively, for 24 h exposure time. SEM and EDX spectra reveal that the adsorptions of corrosion inhibitors on X-60 mild steel create a protective film that serves as a barrier to mitigate the corrosion process. The X-ray photoelectron spectroscopy confirmed the chemical interaction between the corrosion inhibitors and mild steel, which was predicted by the Langmuir adsorption model. Assembly of inhibitive motifs of the alkyne, π-electron-rich aromatic, quaternary ammonium and C12 alkyl chain hydrophobe in PDAB has augmented its inhibiting action.

Design and Synthesis of a Dual-Purpose Superadsorbent Containing a High Density of Chelating Motifs for the Fast Mitigation of Methylene Blue and Pb(II).

Maleic acid underwent alternate copolymerization with diallylaminomethylphosphonic acid·HCl [(CH2=CHCH2)2NH+CH2PO3H2 Cl-] and a cross-linker to give a new pH-responsive resin. Methylene blue (MB) removal from its 3000 ppm solution by the resin at pH 7 followed second-order kinetics with an E a of 34.8 kJ mol-1. MB removal was achieved very fast (10 min), attaining over 98.5% at 328 K. The q e obtained using MB concentrations in the range 100-8000 ppm fitted the Langmuir nonlinear isotherm model to give ΔG o, ΔH o, and ΔS o values of ≈ -21 kJ, 36.5 kJ mol-1, and 185 J mol-1 K-1, respectively. The resin is a superadsorbent with a q max value of 2445 mg g-1. The adsorbent also removed 97% Pb(II) within 5 min from its 10 000 ppb solution. The resin reduced the Pb(II) concentration from 200 to 3.8 ppb. The resin also demonstrated its ability to remove contaminants from industrial wastewater, reducing priority metal contaminants to ppb and sub-ppb levels. The resin can be recycled with stable efficiency. The outstanding performance places the resin in a top position in a list of recently reported sorbents.

Comparative Studies of the Corrosion Inhibition Efficacy of a Dicationic Monomer and Its Polymer against API X60 Steel Corrosion in Simulated Acidizing Fluid under Static and Hydrodynamic Conditions.

N 1,N 1-diallyl-N 6,N 6,N 6-tripropylhexane-1,6-diaminium chloride (NDTHDC) and its polymer poly(N 1,N 1-diallyl-N 6,N 6,N 6-tripropylhexane-1,6-diaminium chloride) (poly-NDTHDC) were synthesized and tested against API X60 carbon steel corrosion in 15 wt % HCl solution. Weight loss, electrochemical, and surface analysis techniques were used. Results show that poly-NDTHDC is better than NDTHDC. Moreover, 1000 mg/L NDTHDC protected the studied surface by 79.1% at 25 °C, while 100 mg/L poly-NDTHDC afforded 86.1% protection. Inhibition efficiency increases with temperature (up to 60 °C) but depreciates thereafter. NDTHDC and poly-NDTHDC perform better under the hydrodynamic condition than the static condition. TGA and FTIR results reveal that poly-NDTHDC is chemically and thermally stable.

Assessment of sulfonated homo and co-polyimides incorporated polysulfone ultrafiltration blend membranes for effective removal of heavy metals and proteins.

Sulfonated homo and co- polyimide (sPI) were synthesized with new compositional ratios, and used as additives (0.5 wt%, 0.75 wt%, and 1.0 wt%) to prepare blend membranes with polysulfone (PSf). Flat sheet membranes for ultrafiltration (UF) were casted using the phase inversion technique. Surface morphology of the prepared UF membranes were characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Surface charge of the membranes were determined by zeta potential, and hydrophilicity was studied by contact angle measurement. The contact angle of the membrane decreased with increasing sPI additive indicates increasing the hydrophilicity of the blend membranes. Filtration studies were conducted for rejection of heavy metals (Pb2+ and Cd2+) and proteins (pepsin and BSA). Blend membranes showed better rejection than pure PSf membrane. Among the blend membranes it was observed that with increasing amount of sPIs enhance the membrane properties and finally, PSf-sPI5 membrane with 1 wt% of sPI5 showed the improved permeability (72.1 L m-2 h-1 bar-1), and the best rejection properties were found for both metal ions (≈98% of Pb2+; ≈92% of Cd2+) and proteins (>98% of BSA; > 86% of Pepsin). Over all, this membrane was having better hydrophilicity, porosity and higher number of sites to attach the metal ions. Its performance was even better than several-reported sulfonic acid based UF membranes. All these intriguing properties directed this new UF membrane for its potential application in wastewater treatment.

Synthesis, characterization, and utilization of a diallylmethylamine-based cyclopolymer for corrosion mitigation in simulated acidizing environment.

A novel random copolymer 4, containing diallylmethylamine and N1,N1-diallyl-N1-methyl-N6,N6,N6-tripropylhexane-1,6-diammonium dibromide units in a 1:1 ratio (polymer 4) was synthesized via Butler's cyclopolymerization technique. Characterization was accomplished by 1H NMR, elemental analysis, and Fourier-transform infrared spectroscopy (FTIR). Polymer 4 was tested as corrosion inhibitor for low carbon steel in 15% HCl solution via gravimetric and electrochemical approaches. The analysis of the metal specimen surfaces was done using scanning electron microscope (SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDAX), and X-ray photoelectron spectroscopy (XPS) methods. Polymer 4 is inhibitor for the substrate particularly at elevated temperatures. Corrosion mitigation is by chemisorption mechanism and can be best described with the Langmuir and El-Awady et al. kinetic-thermodynamic adsorption isotherms. Polymer 4 corrosion mitigation capacity can be improved by the addition of a minute amount of I- ions. Inhibition efficiency of 92.99% has been achieved with 500 ppm polymer 4 + 1 mM KI mixture at 25 °C. Surface analysis results support the claim of adsorption of additive molecules on steel surface. From XPS results, corrosion products on steel surface exposed to the free acid solution are mixtures of chlorides, carbonates, oxides, and hydroxides. In polymer 4 + KI system, polymer 4 molecules are adsorbed on triiodide and pentaiodide ions layer. The improved corrosion inhibition of polymer 4 by I- ions is synergistic in nature according to calculated synergism parameter. Polymer 4 is a promising corrosion inhibitor for oil well acidizing purpose.

Fast removal of methylene blue and Hg(II) from aqueous solution using a novel super-adsorbent containing residues of glycine and maleic acid.

The alternate cyclo-copolymerization of diallylammonioethanoate [(CH2=CHCH2)2NCH2CO2-] and maleic acid in the presence of a cross-linker afforded a novel pH-responsive resin (90% yield). The resin has turned out to be a super-adsorbent for methylene blue (MB) removal with a qMax of 2101 mg g-1. The adsorption of the dye followed pseudo second-order kinetics with an energy of activation (Ea) of 31.5 kJ mol-1. The process showed an extraordinarily fast adsorption rate owing to faster film diffusion; the resin (250 mg) was able to trap 78 and 99.4% MB from its 3000 mg L-1 solution (100 mL) within 3 and 30 min, respectively. Equilibrium constants from Langmuir nonlinear isotherm model in the range 288-328 K gave ΔGo ΔHo, and ΔSo values of ≈ -25 kJ, -13 kJ and 39.5 J mol-1 K-1, respectively. Immobilization mechanism was discussed using FTIR, SEM, and Elovich kinetic model. The presence of the chelating glycine residues was exploited for the removal of Hg(II) ions; the qHg was determined to be 263 mg g-1. The resin also removed MB and Hg(II) simultaneously from industrial wastewater with remarkable efficacy. The very impressive performance along with efficient recycling conferred the resin a top position among many sorbents.

Utilization of catecholic functionality in natural safrole and eugenol to synthesize mussel-inspired polymers.

Naturally occurring safrole I upon epoxidation gave safrole oxide II, which underwent ring opening polymerization using a Lewis acid initiator/catalyst comprising of triphenylmethylphosphonium bromide/triisobutylaluminum to afford new polyether III in excellent yields. Epoxy monomer II and allyl glycidyl ether IV in various proportions have been randomly copolymerized to obtain copolymer V. A mechanism has been proposed for the polymerization reaction involving chain transfer to the monomers. A strategy has been developed for the deprotection of the methylene acetal of V using Pb(OAc)4 whereby one of the methylene protons is replaced with a labile OAc group to give VI. The pendant allyl groups in VI have been elaborated via a thiol-ene reaction using cysteamine hydrochloride and thioglycolic acid to obtain cationic VII and anionic VIII polymers, both containing a mussel-inspired Dopa-based catechol moiety. During aqueous work up, the protecting group containing OAc was deprotected under mild conditions. Cationic VII and anionic VIII were also obtained via an alternate route using epoxide IX derived from 3,4-bis[tert-butyldimethylsilyloxy]allylbenzene. Monomer IX was homo- as well as copolymerized with IV using Lewis acid initiator/catalyst system to obtain homopolymer X and copolymer X1. Copolymer XI was then elaborated using a thiol-ene reaction followed by F- catalysed silyl deprotection to obtain mussel inspired polymers VII and VIII, which by virtue of having charges of opposite algebraic signs were used to form their coacervate.

A new resin embedded with chelating motifs of biogenic methionine for the removal of Hg(II) at ppb levels.

Cyclopolymerization of N,N-diallylmethionine hydrochloride, derived from the biogenic amino acid methionine, (90 mol%) and cross-linker tetraallylpiperazinium dichloride (10 mol%) in presence of an azo-initiator afforded pH-responsive cross-linked polyzwitterion (CPZ). The structural morphology of the resin (i.e. CPZ) was examined by the BET and FESEM-EDX analyses. The methionine embedded resin demonstrated remarkable efficacies for the removal of Hg(II) ions at ppb levels. A 50 mg-dose of the resin immersed in aqueous medium (18 mL) could reduce the concentration of Hg(II) from 200 and 400 ppb to 1.8 and 4.4 ppb, respectively, within 15 min. The resin has also proven to be remarkably effective in the removal of several toxic and priority metal pollutants from industrial wastewater. The Hg(II) adsorption followed pseudo second-order process with Ea of 48.1 kJ mol-1. The initial rapid adsorption of metal ions and subsequent slower adsorption was attributed to film and intraparticle diffusion, respectively. The SEM-EDX analyses revealed the attachment of Hg(II) ions onto the resin. The favorability of the endothermic adsorption was ensured by the negative ΔGº values. The efficient adsorption/desorption process confirmed the recyclability of the resin. The current resin demonstrated superior metal removal capacities as compared to several other adsorbents in recent works.

Isoxazolidine derivatives as corrosion inhibitors for low carbon steel in HCl solution: experimental, theoretical and effect of KI studies.

Two isoxazolidine derivatives namely 5-(benzo[d][1,3]dioxol-5-ylmethyl)-2-tetradecyl isoxazolidine (BDMTI) and 5-(4-hydroxy-3-methoxybenzyl)-2-tetradecyl isoxazolidine (HMBTI) were synthesized and characterized using FTIR, C-NMR, H-NMR, and elemental analysis. The synthesized compounds were evaluated as corrosion inhibitors for API 5L X60 steel in 1 M HCl in the temperature range of 25-60 °C using gravimetric and electrochemical (Electrochemical Impedance Spectroscopy (EIS), Potentiodynamic Polarization (PDP) and Linear Polarization Resistance (LPR)) techniques. The effect of addition of a small amount of iodide ions on the corrosion inhibition performance of the compounds was also assessed. In addition, quantum chemical calculations and Monte Carlo simulations were employed to correlate the electronic properties of the compounds with the corrosion inhibition effect as well as to evaluate the adsorption/binding of the inhibitor molecules on the steel surface. Experimental results show that the two compounds inhibited the corrosion of carbon steel in an acid environment with HMBTI showing superior performance. The corrosion inhibition effect was found to be dependent on the inhibitors' concentration and temperature. Addition of iodide ions improves the inhibition efficiency considerably due to co-adsorption of the iodide ions and the inhibitors on the steel surface which was competitive in nature as confirmed from the synergistic parameter (S 1) which was less than unity at higher temperature. Experimental and theoretical results are in good agreement.

Scope of sulfur dioxide incorporation into alkyldiallylamine-maleic acid-SO2 tercyclopolymer.

Alternate copolymerization of diallylamine derivatives [(CH2CH[double bond, length as m-dash]CH2)2NR; R = Me, (CH2)3PO(OEt)2, and CH2PO(OEt)2] (I)-maleic acid (MA) and (I·HCl)-SO2 pairs have been carried out thermally using ammonium persulfate initiator as well as UV radiation at a λ of 365 nm. The reactivity ratios of ≈0 for the monomers in each pair I-MA and I·HCl-SO2 ensured their alternation in each copolymer. However, numerous attempted terpolymerizations of I-MA-SO2 failed to entice MA to participate to any meaningful extent. In contrast to reported literature, only 1-2 mol% of MA was incorporated into the polymer chain mainly consisting of poly(I-alt-SO2). Quaternary diallyldialkylammonium chloride [(CH2[double bond, length as m-dash]CH-CH2)2N+R2Cl-; R = Me, Et] (II) also, did not participate in II-MA-SO2 terpolymerizations. Poly((I, R = Me)-alt-SO2) III is a stimuli-responsive polyampholyte; its transformation under pH-induced changes to cationic, polyampholyte-anionic, and dianionic polyelectrolytes has been examined by viscosity measurements. The pK a of two carboxylic acid groups and NH+ in III has been determined to be 2.62, 5.59, and 10.1. PA III, evaluated as a potential antiscalant in reverse osmosis plants, at the concentrations of 5 and 20 ppm, imparted ≈100% efficiency for CaSO4 scale inhibition from its supersaturated solution for over 50 and 500 min, respectively, at 40 °C. The synthesis of PA III in excellent yields from cheap starting materials and its very impressive performance may grant PA III a prestigious place as an environment-friendly phosphate-free antiscalant.

Polyaspartate extraction of cadmium ions from contaminated soil: Evaluation and optimization using central composite design.

The occurrences of heavy metal contaminated sites and soils and the need for devising environmentally friendly solutions have become global issues of serious concern. In this study, polyaspartate (a highly biodegradable agent) was synthesized using L-Aspartic acid via a new modified thermal procedure and employed for extraction of cadmium ions (Cd) from contaminated soil. Response surface methodology approach using 35 full faced centered central composite design was employed for modeling, evaluating and optimizing the influence of polyaspartate concentration (36-145mM), polyaspartate/soil ratio (5-25), initial heavy metal concentration (100-500mg/kg), initial pH (3-6) and extraction time (6-24h) on Cd ions extracted into the polyaspartate solution and its residual concentration in the treated soil. The Cd extraction efficacy obtained reached up to 98.8%. Increase in Cd extraction efficiency was associated with increase in the polyaspartate and Cd concentration coupled with lower polyaspertate/soil ratio and initial pH. Under the optimal conditions characterized with minimal utilization of the polyaspartate and high Cd ions removal, the extractible Cd in the polyaspartate solution reached up to 84.4mg/L which yielded 85% Cd extraction efficacy. This study demonstrates the suitability of using polyaspartate as an effective environmentally friendly chelating agent for Cd extraction from contaminated soils.

Tailoring hydrophobic branch in polyzwitterionic resin for simultaneous capturing of Hg(II) and methylene blue with response surface optimization.

A new highly efficient cross-linked polymer was synthesized via cyclotetrapolymerization of hydrophilic [(diallylamino)propyl]phosphonic acid hydrochloride (72 mol%), hydrophobic N,N-diallyl-1-[6-(biphenyl-4-yloxy)hexylammonium chloride (18 mol%), cross-linker 1,1,4,4-tetraallylpiperazinium dichloride (10 mol%) with an equivalent amount of alternating SO2 units (100 mol%). The pH-responsive resin chemically tailored with the aminopropylphosphonate chelating ligand and hydrophobic chain of (CH2)6OC6H4-C6H5 is designed to capture toxic metal ions and organic contaminants simultaneously. The developed resin was used for the remediation of Hg(II) ions and methylene blue from aqueous solutions as models. The experimental conditions were optimized utilizing the response surface methodology as an environmentally friendly method. The adsorption efficiency for Hg(II) was ≈100% at 10 ppm initial concentration at pH 5 at 25 °C, while it was 80% for removal of the dye in a single pollutant system. Interestingly, the resin demonstrated its remarkable efficacy in the simultaneous and complete removal of Hg(II) and the dye from their mixture. Increased removal of the dye (≈100%) in the presence of Hg(II) was attributed to the synergistic effect. The equilibrium data were evaluated by employing the Langmuir and Freundlich isotherm models.

Biogenic glutamic acid-based resin: Its synthesis and application in the removal of cobalt(II).

Inexpensive biogenic glutamic acid has been utilized to synthesize a cross-linked dianionic polyelectrolyte (CDAP) containing metal chelating ligands. Cycloterpolymerization, using azoisobutyronitrile as an initiator, of N,N-diallylglutamic acid hydrochloride, sulfur dioxide and a cross-linker afforded a pH-responsive cross-linked polyzwitterionic acid (CPZA) which upon basification with NaOH was converted into CDAP. The new resin, characterized by a multitude of spectroscopic techniques as well as Scanning Electron Microscopy (SEM) and Brunauer-Emmett-Teller (BET) analyses, was evaluated for the removal of Co(II) as a model case under different conditions. The adsorption capacity of 137mgg-1 does indeed make the resin as one of the most effective sorbents in recent times. The resin leverages its cheap natural source and ease of regeneration in combination with its high and fast uptake capacities to offer a great promise for wastewater treatment. The resin has demonstrated remarkable efficiency in removing toxic metal ions including arsenic from a wastewater sample.

Synthesis of hydrophobic cross-linked polyzwitterionic acid for simultaneous sorption of Eriochrome black T and chromium ions from binary hazardous waters.

Hydrophobic cross-linked polyzwitterionic acid (HCPZA) containing long chain (C18) hydrophobes and residues of a glutamic acid having unquenched nitrogen valency was synthesized. Exploiting the chelating ability of the amino acid residues to scavenge toxic metals and the hydrophobic surface to scoop up the organic contaminants, the resin HCPZA was evaluated for simultaneous removal of chromium and Eriochrome black T (EBT) from wastewaters. The structure and morphology of the polymer before and after sorption were characterized by using FTIR, TGA, EDX and SEM. The effect of various parameters such as contact time, pH and initial concentrations were investigated to arrive at optimum conditions. The adsorption of Eriochrome black T and Cr (III) on HCPZA reached equilibrium in 30 min. The mechanism of adsorption was investigated using kinetic, diffusion and isotherm models. The adsorption kinetic data were described well by the pseudo-second order model and by the Freundlich isotherm model. EDX analysis confirmed the adsorption of Cr (III) and EBT on the polymer. The hydrophobic resin exhibited a remarkable simultaneous adsorption capacity for EBT and Cr (III) and thus demonstrated its potential to be a promising adsorbent for removal of dyes and heavy metal ions from wastewaters.