Removal Of Cations Research Articles

Enhanced removal of heavy metals by α-FeOOH incorporated carboxylated cellulose nanocrystal: synergistic effect and removal mechanism.

Simultaneous and highly efficient removal of heavy metal cations and oxyanions is significant for both water and soil remediation, but it remains a major challenge due to the complexity. In this work, a novel hybrid of α-FeOOH incorporated carboxylated cellulose nanocrystal (Fe/CNC) is synthesized via a hydrothermal process, which shows improved α-FeOOH dispersion and heavy metal removal capacity. In single adsorbate system, maximum adsorption capacities toward Pb(II), Cd(II), and As(V) by Fe/CNC reach 126.06, 53.07, and 15.80mgg-1, respectively, and the Fe leaching is much lower than that of α-FeOOH. In binary and ternary adsorption systems, simultaneous removal of Pb(II), Cd(II), and As(V) is proved, and the competition and synergy coexist among heavy metals. FTIR and XPS spectra have revealed the synergistic removal mechanism: Pb(II) and Cd(II) are mainly removed by surface complexation with oxygen-containing functional groups on C-CNC and α-FeOOH, and precipitation on the surface of α-FeOOH, while ligand exchange with Fe-OH is responsible for As(V) removal. The soil incubation experiments show that exchangeable and carbonate-bound Pb, Cd, and As are transformed into more stable forms in contaminated soil containing Fe/CNC composites. This work provides a novel composite material for remediation of heavy metal-contaminated environments.

Statistically optimized sequential hydrothermal route for FeTiO3 surface modification: evaluation of hazardous cationic dyes adsorptive removal.

In the present study, the performance of facile hybrid sequential chemical treatments of titanomagnetite concentrate (TC), alkaline leaching, and sodium dodecyl sulfate (SDS) modification has been evaluated for the removal of crystal violet (CV), malachite green (MG), and methylene blue (MB) cationic dyes. The physical and chemical properties of samples were characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), N2 adsorption-desorption, X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and Fourier transform infrared spectroscopy (FTIR) analyses. Moreover, dye removal in the batch system was investigated by evaluating adsorbent dosage, contact time, initial dye concentration, pH of the solution, temperature, electrolyte concentration, adsorption isotherm, kinetic, and thermodynamic. The results showed that the maximum adsorption capacity was obtained at SDS concentration of 6mM, NaOH concentration of 9M, the temperature of 160°C, solid/liquid ratio of 4g/100mL, and the process duration of 24h. In the alkaline leaching process, forming the Na2TiO3 phase with sharp and high energy points can be improved the adsorption properties. Accordingly, the adsorption capacity and removal efficiency attained 19.84, 18.64, and 19.66mg/g and 99.21, 93.24, and 98.31% for CV, MG, and MB, respectively. Furthermore, the dye removal followed pseudo-second-order (R2 = 0.9990) and Freundlich (R2 = 0.9970) models. The evaluation of thermodynamic parameters indicated the endothermic (∆H° = 110.91J/mol) and spontaneous nature (ΔG˚ < 0) of the adsorption process. This study concluded that the modified TC had a potential ability for application in textile wastewater treatment.

Selective and Chemical-Free Removal of Toxic Heavy Metal Cations from Water Using Shock Ion Extraction.

Electrochemical methods are known to have attractive features and capabilities when used for ion separations and water purification. In this study, we developed a new process called shock ion extraction (shock IX) for selective and chemical-free removal of toxic heavy metals from water. Shock IX is a hybrid process that combines shock electrodialysis (shock ED) and ion exchange using an ion exchange resin wafer (IERW), and this method can be thought of functionally as an electrochemically assisted variation of traditional ion exchange. In particular, shock IX exhibits greater ion removal and selectivity for longer periods of time, compared to the use of ion exchange alone. The use of an IERW in shock ED also increases multivalent ion selectivity, reduces energy consumption, and improves the hydrodynamics and scalability of the system.

Synthesis and application of treated activated carbon for cationic dye removal from modelled aqueous solution

Use of activated carbon (AC) prepared from rice husk and treated with anionic surfactant is investigated to eliminate cationic dye crystal violet (CV) using modelled dye solution. AC modified with anionic surfactant sodium lauryl sulfate (ACSLS) and other two surfactant namely sodium dodecyl sulfonate and hexadecyl trimethyl ammonium bromide were used for the analysis. Optimum ACSLS was analyzed and characterized using BET, XRD, SEM accompanied with XEDS, FTIR, HR-TEM and zeta potential, which confirms the sorption of CV onto ACSLS. Influence of pH, dose of adsorbent, concentration of initial dye, contact time, additive salts as well as actual water samples were investigated. Presence of NH4+, Ca2+, Mg2+, Na2+, Ca2+and K+cations in dye solution were having negligible (less than 4 %) influence on dye removal capacity. Study of mass transfer parameters revealed intra particle diffusion and film diffusion both played their part, whereas other kinetic studies has shown that experimental data fitted best with Pseudo 2nd order rate. Isotherm studies accompanied with error analysis revealed that Langmuir isotherm controls the adsorption equilibrium with highest capacity of CV adsorption with optimum operating conditions as pH = 6, temperature = 318 K, adsorbent dose = 100 mg/L and dye concentration = 30–60 mg/L. Study of thermodynamics and temperature analysishave shown that the sorption reaction was favourable and spontaneous with rise in temperature and endothermic in nature. Column studies are reported for varying rate of flow, depth of bed and dye concentrations along with analysis of column experimental data with various models like Yoon-Nelson, Thomas, Bohart-Adam and Clark model. Reusability (no. of cycles) of used adsorbent was studied using regeneration experiments. Analysis inferred that AC modified using surfactants can be a useful technique for enhanced adsorption capacity of dyes from aqueous solution andnot much work has been reported on use of anionic surfactant modified AC for dye removal process.

Cation-π interaction in Mg(OH)2@GO-coated activated carbon fiber cloth for rapid removal and recovery of divalent metal cations by flow-through adsorption

Sorption is considered a promising approach for removing various divalent metal cations, yet the complicated recovery and regeneration strategy restricts the application of powder-like adsorbents. Herein, we report an innovative Mg(OH)2@GO adsorbents loaded on activated carbon fiber cloth (ACFC) using an electrophoretic deposition process (EDP) of Mg(OH)2 and graphene oxide (GO) suspensions to achieve rapid removal of Cd2+, Pb2+, Ni2+, and Cu2+ via flow-through adsorption over an ultra-short period time. FESEM and HRTEM results revealed a cross-linked structure on the ACFC surface derived from the cation-π interaction between Mg2+ and GO under EDP. Importantly, by virtue of oxygen-containing functional groups and π electron region, Mg(OH)2@GO exhibited high adsorption capacities for Pb2+, Cu2+, Cd2+, and Ni2+, which could reach 647.2, 439.5, 297.3, and 219.1 mg g−1 at 293 K, respectively. Furthermore, Mg(OH)2@GO-ACFC possessed a rapid regeneration capability with EDTA by a flow-through system for divalent metal cations desorption and exhibited excellent repeatability in 5-cycle tests. Overall, we propose the novel flow-through system that facilitates the rapid adsorption and recovery of divalent metal cations for wastewater treatment.

A new method for phosphate purification for oxygen isotope ratio analysis in freshwater and soil extracts using solid-phase extraction with zirconium-loaded resin.

Phosphate (PO4 ) oxygen isotope (δ18 OPO4 ) analysis is increasingly applied to elucidate phosphorus cycling. Due to its usefulness, analytical methods continue to be developed and improved to increase processing efficiency and applicability to various sample types. A new pretreatment procedure to obtain clean Ag3 PO4 using solid-phase extraction (SPE) with zirconium-loaded resin (ZrME), which can selectively adsorb PO4 , is presented and evaluated here. Our method comprises (1) PO4 concentration, (2) PO4 separation by SPE, (3) cation removal, (4) Cl- removal, and (5) formation of Ag3 PO4 . The method was tested by comparing the resulting δ18 OPO4 of KH2 PO4 reagent, soil extracts (NaHCO3 , NaOH, and HCl), freshwater, and seawater with data obtained using a conventional pretreatment method. PO4 recovery of our method ranged from 79.2% to 97.8% for KH2 PO4 , soil extracts, and freshwater. Although the recovery rate indicated incomplete desorption of PO4 from the ZrME columns, our method produced high-purity Ag3 PO4 and accurate δ18 OPO4 values (i.e., consistent with those obtained using conventional pretreatment methods). However, for seawater, the PO4 recovery was low (1.1%), probably due to the high concentrations of F- and SO4 2- which interfere with PO4 adsorption on the columns. Experiments indicate that the ZrME columns could be regenerated and used repeatedly at least three times. We demonstrated the utility of ZrME for purification of PO4 from freshwater and soil extracts for δ18 OPO4 analysis. Multiple samples could be processed in three days using this method, increasing sample throughput and potentially facilitating more widespread use of δ18 OPO4 analysis to deepen our understanding of phosphorus cycling in natural environments.

Salt-modified MXene membrane for ultrafast and efficient cationic and anionic dyes removal

MXene, the two-dimensional (2D) transition metal carbides/nitrides, have gained much attention in the application as membranes since the stacking of MXene nanosheets could realize hydrophilic, nanoscale interlayer spacing with remarkable separation performance. Herein, we reported the simple modification of MXene membranes using chloride salts (NaCl, KCl, and MgCl2), which could substantially improve the performance in the separation of cationic (methylene blue, MB) and anionic (congo red, CR) dyes from aqueous solutions. The salts could reside in the membrane surface and penetrate the interlayer galleries as well as the space within the adjacent MXene nanosheets. As a result, the membrane could possess modified nanochannels and altered surface chemistry that improve water transport and dye molecules' retention. In the case of MB filtration, MXene membrane modified with KCl (MM-KCl) exhibits the highest flux (141 L m−2 h−1) and a complete rejection, attributed to the weaker interaction between the water molecules and potassium ion. On the other hand, MM-MgCl2 demonstrates the best performance (flux of 117 L m−2 h−1 and a ∼100 % rejection) in the CR filtration. This could be related to the stronger interaction of anionic dye molecules with the magnesium cation that has the highest positive charge density. All MXene membranes have high flux-recovery ratios and low reversible and irreversible fouling, showing desirable anti-fouling properties.

Wood-Based Self-Supporting Nanoporous Three-Dimensional Electrode for High-Efficiency Battery Deionization.

Developing highly efficient advanced battery deionization (BDI) electrode materials at a low cost is vital for seawater desalination. Herein, a high-efficiency wood-based BDI electrode has been fabricated for seawater desalination, benefiting from the self-supporting three-dimensional (3D) nanoporous structure and rich redox-active sites. The finely tuned rich electrochemical redox active C═O groups on the surface of the wood electrode derived from the facile thermochemical conversion of lignin play a crucial role in the Faradaic cation removal dynamics of BDI. Coupling the 3D wood electrode and a polyaniline-modified wood electrode as the cathode and anode, an all-wood-electrode-based deionization battery has been successfully assembled with a state-of-the-art ion removal capacity of up to 164 mg g-1 in seawater. Our work reported an example of utilizing wood as the BDI electrode via fine-tuning the redox-active sites, demonstrating a novel resource utilization pathway of converting cheap biomass into BDI electrodes for highly efficient seawater desalination.

Cationic dye removal using Pergularia tomentosa L. fruit: kinetics and isotherm characteristics using classical and advanced models

The agricultural crops prove to be low-cost and abundant biosorbents that are able to adsorb dyes from contaminant water. In the present study, different techniques were used to characterize the powdered Pergularia tomentosa fruit. After that, the biomaterial was exploited to investigate the adsorption of methylene blue in batch mode. The effects of initial pH, contact time, dye concentration, biosorbent dose, and temperature on the biosorption capacity have been performed. The fit of the adsorption isotherms was performed by means of several classical models and advanced models derived from statistical physics. The two-energy monolayer model proves to be the more suitable. It appears that two functional groups of the biosorbent are involved in the dye biosorption. The adsorption energy ranges from 14 to 18 kJ·mol -1 which indicates a physiosorption mechanism. The maximum adsorption capacity is 152 mg·g -1 . Pergularia tomentosa fruit proves to be attractive for the efficient removal of cationic dyes from polluted water.

Conversion of teak wood waste into microwave-irradiated activated carbon for cationic methylene blue dye removal: Optimization and batch studies

The objective of this study is to find optimum preparation conditions in converting teak wood waste into activated carbon (TWAC) and to evaluate its performance in adsorbing cationic dye of methylene blue (MB). TWAC was produced via physiochemical activation (potassium hydroxide, KOH chemical treatment, and carbon dioxide, CO 2 gasification) and heated through microwave irradiation technique. With the aid of response surface methodology (RSM), optimized TWAC was successfully synthesized at radiation power, radiation time, and impregnation ratio (IR) of 366 W, 5.30 min, and 1.15 g/g, respectively. These preparation conditions produced TWAC with MB adsorption uptakes of 66.69 mg/g and a yield of 38.23%. Characteristics of TWAC in terms of BET surface area, mesopores surface area, total pore volume, and average pore diameter were determined to be 1345.25 m 2 /g, 878.63 m 2 /g, 0.6140 cm 3 /g, and 2.85 nm, respectively. Isotherm studies divulged that the MB-TWAC adsorption system followed the Langmuir model with a maximum monolayer adsorption capacity of 567.52 mg/g. In terms of kinetic studies, this adsorption system fit pseudo-second order model the best whereas Boyd plot confirmed that the adsorption process was controlled by the film diffusion mechanism. Thermodynamic parameters of enthalpy change, ΔH°, entropy change, ΔS°, Gibbs free energy, ΔG° and Arrhenius activation energy, E a were calculated to be −4.06 kJ/mol, 0.06 kJ/mol.K, –22.69 kJ/mol and 16.03 kJ/mol, respectively. The activation and microwave heating methods employed succeeded to produce TWAC with excellent adsorption performance in removing MB dye. TWAC was also successfully regenerated for 5 cycles via microwave heating technique.

Insight into adsorption mechanism, modeling, and desirability function of crystal violet and methylene blue dyes by microalgae: Box-Behnken design application

Herein, an environmentally friendly and efficient adsorbent of microalgae (MAG) was applied for the removal of crystal violet (CV) and methylene blue (MB) dyes from aqueous solutions. Multivariate modeling and optimization of CV and MB dyes removal onto MAG via Box-Behnken design (BBD) were investigated depending on three variables i.e. MAG dosage (20–100 mg), initial pH (4–10), and adsorption time (2–6 min). The adsorption kinetics and isotherm analyses revealed that the pseudo-second-order and Langmuir models governed the adsorption of CV and MB dyes onto MAG. The maximum adsorption capacity of MAG generated from the Langmuir equation was computed to be 243.0 mg/g for CV and 297.1 mg/g for MB. The determined thermodynamic parameters denoted that the adsorption mode of CV and MB dyes by MAG was spontaneous and endothermic. Several interactions like electrostatic forces, n-π stacking, and H-bonding caused the adsorption process of CV and MB molecules on the surface of MAG. The results showed that MAG could be an effective and locally available candidate adsorbent for removing dyestuffs from contaminated effluents. • Microalgae were applied for the removal of cationic dyes removal (crystal violet, CV) and (methylene blue, MB). • Box–Behnken design was applied to enhance the adsorption process. • The adsorption capacities for CV and MB were 243.0 mg/g and 297.1 mg/g, respectively. • The adsorption mechanism can be assigned to the electrostatic forces, n-π stacking, and H-bonding

Utilization of Amino-Silane Modified Lignin Derivative as an Adsorbent for Cationic Dye Removal

In this study, we evaluated the possibility of the application of amino-silane as a cationic dye adsorbent via chemical modification using lignin. Amino-silane modified lignins (ALs) have been synthesized via amine-silanization. The ALs have high accessibility to pollutants and stability in aqueous solutions owing to their high zeta-potential and specific surface area. Adsorption experiments showed that the ALs exhibited excellent cationic dye removal under neutral and basic conditions. Because ALs contain abundant amine groups, having a lone pair of electrons confers excellent accessibility via electrostatic attraction with cationic dyes. The maximum adsorption amount of the cationic dye reached 197.44 mg·gSUP-1/SUP. All adsorption processes followed the pseudo-second-order kinetics, Langmuir and Temkin isotherm models, and spontaneous processes. Therefore, this study contributes to the development of a low-cost and sustainable lignin-based adsorbent.

Dual-engineering of ammonium vanadate for enhanced aqueous and quasi-solid-state zinc ion batteries

Ammonium vanadate holds promise for the high-performance cathode in aqueous zinc ion batteries (ZIBs) due to its stable layered structure and superior theoretical capacity. However, excessive ammonium cations occupying the interlayer and too strong electrostatic interaction between Zn2+ and defect-free V-O bonds largely hinder the capacity and rate performance of ammonium vanadate in ZIBs. Here, in this work, a dual-engineering method that integrates the partial removal of ammonium cations and the increase of oxygen vacancies has been proposed to boost the performance of NH4V4O10 (NVO). Experimental evidence and theoretical calculations demonstrate that this method can ensure an enlarged room for the (de)intercalation of more Zn2+ ions and weaken the strong electrostatic interaction between the V-O layer and Zn2+ to reduce the energy barrier of the Zn2+ diffusion process. As a consequence, the specific capacity of the as-obtained NVO with the above dual characteristic (NVO-300) was enhanced from 304 mAh g−1 to 355 mAh g−1, relative to the NVO without dual characteristic. And the rate capability of NVO-300 has a more than 300% increase relative to NVO. Furthermore, benefiting from the superior performance and self-supporting feature of this NVO-300, a quasi-solid-state ZIB based on NVO-300 displays a satisfactory specific capacity of 307 mAh g−1 at 0.5 A g−1 and a high energy density of 214 Wh kg−1 at 345 W kg−1, demonstrative of its great usage potential as a practical portable energy storage device.

The distinctive role of nano-hydroxyapatite modified biochar for alleviation of cadmium and arsenic toxicity in aqueous system

The synergetic behavior of cadmium and arsenic in water is characterized by increased mobility and toxicity. The control of Cd and As toxicity is one of the greatest environmental challenges in the world. Biochar with a strong adsorption affinity for cations is considered to sequester Cd(II). However, little is known about whether biochar and its modified materials are efficient in the removal of cations and anions in a dual system. In this study, wheat straw and nanohydroxyapatite were used to prepare nanohydroxyapatite-modified biochar (HBC) and to control cationic Cd(II) and anionic As(III) in water. As the mass ratio of nHAP to wheat straw biochar was increased from 0.1 % to 1.0 %, the amount of nHAP particles loaded on the surface of BC increased, and the particles tended to aggregate. In the single and binary contaminant systems, the maximum Langmuir adsorption capacities of HBC for Cd(II) and As(III) were 55.95 and 14.84 and 14.24 and 12.44 mg/g, respectively. Cd and As adsorption by HBCs was influenced by physical adsorption, electrostatic interactions, hydroxyl groups, and surface complexation, accompanied by specific adsorption induced by HAP particles on HBCs. The findings of the current investigation showed that HBCs can be used as green and low-cost amendments, which would help in the treatment of wastewater contaminated by multiple heavy metals.

Positively Charged Poly(Piperazinamide) Nanofiltration Membranes for the Fast Removal of Metal Ions

AbstractPositively charged nanofiltration (NF) membranes with high perm‐selectivity are highly desired to remove divalent cations such as Ca2+ and Mg2+ ions to ensure the safety of domestic and industrial water supply. In this work, a poly(piperazinamide) NF membrane with a positively charged surface is fabricated via the surfactant‐assembly regulated interfacial polymerization (SARIP) of piperazine (PIP) and 1,3,5‐trimesoyl chloride (TMC). The surfactant assembly can accelerate PIP monomer into the hexane to react with TMC monomer, thus reducing the difference in the trans‐interface diffusion of PIP and the diffusion of TMC in hexane, forming an interfacial polymerization with a stoichiometric characteristic. By tuning the concentration ratio of PIP and TMC, a positively charged poly(piperazinamide) NF membrane will be achieved. At the same time, utilizing the superior hydrophilicity of bacterial cellulose nanofibers nanofilm, a crumpled poly(piperazinamide) active layer is successfully constructed, resulting in a permeating flux up to 22 L m−2 h−1 bar−1 and simultaneously with a MgCl2 rejection &gt;96%. The performance of this positively charged poly(piperazinamide) NF membrane is superior to most other positive NF membranes for the removal of divalent cations so far.

Molecular Size-Selective Electrodialytic Desalters for Electrospray Ionization-Mass Spectrometry.

A membrane-based electrodialytic desalter has been developed for the selective removal of buffer/salt constituents from a fluid stream while retaining larger charged molecules such as proteins prior to mass spectrometric (MS) detection. The salts are deleterious to MS causing signal suppression, formation of adducts, and eventual contamination of the inlet. The new device uses dialysis membranes (DMs) paired with ion exchange membranes (IEMs) flanking the carrier flow channel in a planar configuration. The DMs contact the carrier channel preventing adsorptive losses of large, charged molecules to the IEMs. Ions are removed under an applied electric field using four pairs of electrodes along the flow channel. Removal of both anions and cations is more energy intensive than conversion of a suitable MS friendly salt into its respective acid or base, for example, ammonium acetate into acetic acid. The energetics and optimal voltage profiles for both scenarios have been thoroughly investigated. The DMs resulted in nonlinear increases in energy required for desalting over standard IEM devices due to electroosmotic flow of water into the interstitial space between the membranes. For a device channel with nominal volume of 15.2 μL, a maximum concentration of 200 mM ammonium acetate flowing at 0.25 mL/min was converted into acetic acid. Recovery of bovine serum albumin measured at 280 nm was 67%-96% at tested salt concentrations, and dispersion volumes were less than 200 μL2 and may be suitable for coupling to liquid chromatography.

Comparison of ion removal from waste fermentation effluent by nanofiltration, electrodialysis and ion exchange for a subsequent sulfuric acid recovery

Nutrient recovery from wastewater in the form of acids/bases by electrodialysis with bipolar membranes or diffusion dialysis facilitates the current demand for a green economy and circular production. However, bipolar membranes are sensitive to scaling, mainly by calcium and magnesium salts, as well as to biofouling caused by microbial growth and linked aspects. This work aimed to reduce divalent cations to a value below 10 ppm and DOC content of a residual liquid waste stream after microbial fermentation and before a bipolar electrodialysis/diffusion dialysis step for nutrient and acid/base recovery. In this context, three pretreatment technologies were analyzed: nanofiltration, electrodialysis with monovalent cation-exchange membranes, and ion-exchange resins. Nanofiltration and electrodialysis with monovalent cation-exchange membrane were demonstrated to be suitable pretreatments with 92–96 % Mg2+ and Ca2+ removal and 86–94 % DOC removal. Ion-exchange resins had excellent divalent cation removal but no DOC removal, therefore requiring additional treatment to remove organic substances and prevent membranes’ biofouling. Electrodialysis with monovalent cation-exchange membranes was preferable over nanofiltration due to the 1.6-fold concentration factor for sulfate ions. In contrast, nanofiltration had lower energy consumption and higher stability in divalent cation rejection. Results obtained in this study are valuable for selecting an appropriate treatment for resource recovery and water reclamation from industrial wastewater and for biotechnological downstream processes.

The Influence of Anion-Stripped MIL-101(Cr) Dispersed in Thin-Film Polyvinyl Alcohol Membrane Matrix on the Methylene Blue Dye Separation

This study investigates the production and performance of a novel nanofiltration membrane for removal of cationic dye (Methylene blue) and multivalent cations. These positively charged membranes are made by dispersing a modified cationic metal–organic framework, Cl-MIL-101(Cr), into the polyvinyl alcohol matrix as a membrane skin layer. To this end, the mobile anion (Cl−) embedded in the MIL-101(Cr) structure plays a role to create a positive partial charge on the membrane. In this study, the effects of MOF content and their types on the membrane structure were considered by FTIR, XRD, FESEM, Zeta potential and water contact angle. The results have shown that membranes filled with Cl-MIL-101(Cr) attained higher permeate flux and rejection than those of MIL-101(Cr). Particularly, this study indicates that the low irreversible resistance (19.49%) and high flux return ratio (80.50%) have been related to the membrane containing 15% cationic Cl-MIL-101(Cr). However, this membrane rejected more than 30.41% of AlCl3 salt and 99.08% of methylene blue with approximate permeate flux of 20 L/m2·h. It is recommended that the fabricated membrane be placed in the flow path process of cationic dyes purification.

Gamma irradiation synthesis of pectin- based biohydrogels for removal of lead cations from simulated solutions

Bio-based hydrogels (denoted as PC-PAAc/GA) comprised of Pectin (PC) and polyacrylic acid (PAAc) reinforced with different ratios of gallic acid (GA) were prepared by gamma radiation at irradiation dose 20 kGy. The prepared hydrogels were investigated by different analytical tools. The swelling performance was studied versus time, pH of the medium and gallic acid content. The experimental data depicted that the swelling increases with pH of medium until the equilibrium of swelling after 350 min. The maximum swelling was attained at pH10 for both PC-PAAc and PC-PAA/GA1.5. Also, the data reveal that the incorporation of GA in the hydrogel matrix enhanced the swelling performance of the hydrogel up to an optimum value of GA, i.e. PC-PAA/GA1.5. Further increase in GA concentration leads to formation of a highly crosslinked structure with reduced swelling. The results demonstrated that the prepared hydrogels displayed excellent antibacterial activity against gram + ve bacteria (E.coli) and gram-ve bacteria (S.aureus). This potent antimicrobial activity is mainly originated from GA which was proved as a strong antibacterial agent. Moreover, the removal performance of the investigated hydrogels was verified towards Pb+2 cation as one of the most poisonous heavy metals. The data revealed that the maximum removal percentage of Pb (II) was attained by PC-PAAc/GA1.5 hydrogel (90 mg g−1). The correlation coefficients of the Langmuir model are too higher than that of the Freundlich model that assumed the adsorption of lead cations is mainly a chemical process.

New pyridyl and aniline-functionalized carbamoylcarboxylic acids for removal of metal ions from water by coagulation-flocculation process

In this work, a library of new aniline and pyridyl functionalized carbamoylcarboxylic acids were synthesized, physicochemically analyzed and evaluated as ligands for the simultaneous removal of environmental interest cations. The effect of the structural characteristics of these functionalized ligands over the simultaneous removal performance of metal ions (Cr3+, Pb2+, Cd2+, Cu2+, Ni2+, Zn2+ and Ca2+) was established. The metal ion-ligand association constants calculated from zeta potential (102 to 104 M−1) and UV–vis (103 to 107 M−1) demonstrate a strong affinity of these ligands towards metal ions. The micro-Jar test for cation removal shows these new functionalized carbamoylcarboxylic acids L1-L12 show average removal efficiencies of 100 % Cr3+, 73 % Pb2+, 42 % Zn2+, 50 % Ni2+, 42 % Cd2+, 39 % Cu2+ and 30 % Ca2+. The quantification of destabilization phenomena through transmittance and backscattering measurements allowed to evaluate the mechanisms of colloidal instability to all ligands. Among the twelve ligands, L9 showed the best removal performance at pH = 4.0 with an overall removal capacity (19.28 mg Mn+ removed/mg of L9), clarification kinetics (55.99 T%/h) and sedimentation ratio (117.6 mm/h). The flocs recovered from the coagulation-flocculation tests were analyzed by scanning electron microscopy and dispersive energy spectroscopy with mapping finding the dispersion patterns of metals on the surface. A BOD5/COD = 0.44 indicates that L9 is a biodegradable compound. Based on the results, aniline and pyridyl functionalized carbamoylbenzoic acids have great potential to be applied in the wastewater treatment industry containing multiple cations.