Selective mercury uptake by polymer supported hydroxyethyl sulfonamides

Hydroxyethyl sulfonamide function supported on styrene-divinyl benzene (9% mol/mol) bead resin is presented as mercury selective reagent. The resin product with 3.49 mmol g(-1) of 2-hydroxyethyl sulfonamide content removes reasonable quantities of mercuric ions (0.83-1.64 mmol g(-1)) from aqueous solutions of HgCl2, Hg (CH3COO)(2) and Hg (NO3)(2), in non-buffered conditions. Experiments showed that, the resin is able to extract mercury selectively, in the presence of foreign ions such as Zn(II), Cd(II), Fe(III), and Pb(II). Only negligible amount of sorption was detected for the case of Fe(III) (0.31 mmol g(-1))

Removal of hexavalent chromium anions via polymer enhanced ultrafiltration using a fully ionized polyelectrolyte

A fully ionized polyelectrolyte was synthesized for Cr(VI) removal from aqueous solutions by continuous polymer enhanced ultrafiltration (PEUF). Effect of operating parameters such as pH, loading, polymer, and competing ion concentrations were examined. Highest Cr(VI) retention was obtained at a loading of 0.01 at pH 4. Increasing both polymer and chromate concentrations at a fixed loading of 0.01 decreased the retention which demonstrated the effect of crowding. In the presence of competing anions such as chloride and sulfate, Cr(VI) retention decreased for all of the pH values studied. Even at high competing anion concentrations, significant retentions of Cr (VI) were obtained

Estimation of Binding Constants of Cd(II), Ni(II) and Zn(II) with Polyethyleneimine (PEI) by Polymer Enhanced Ultrafiltration (PEUF) Technique

Continuous and batch processes of polymer enhanced ultrafiltration for the estimation of binding constants of divalent cadmium, nickel, and zinc ions have been elaborated. Polyethyleneimine was used as a complexation agent. Effect of pH and ionic strength on the binding ability of target metal ions to polyethyleneimine were estimated by continuous mode PEUF system. A mathematical model was developed to estimate apparent complexation constants of metal ions with PEI. The development of this model, which is in good agreement with experimental data, enables to compare the data obtained in both continuous and batch system and correlate the effect of pH and ionic strength with apparent binding constants

Removal of Heavy Metals from Multicomponent Metal Mixtures by Polymer Enhanced Ultrafiltration: Effects of pH, Ionic Strength and Conformational Changes in Polymer Structure

Fractional separation of industrially important heavy metals (cadmium, nickel, zinc) from binary and ternary metal mixtures by continuous mode polymer enhanced ultrafiltration was studied. Polyethyleneimine (PEI) was used as a complexation polymer. Effects of pH and ionic strength on process efficiency were investigated. To gain insight about the characteristics of binding between highly branched PEI and metal ions and effect of salt concentration on this binding were investigated by performing dynamic and static light scattering measurements. It was observed that with optimum pH and salt concentration, fractional separation of metals can be achieved

Kinetic investigation of chemical vapor deposition of B4C on tungsten substrate

Production of beta-rhombohedral boron carbide (B4C) on a tungsten substrate by the chemical vapor deposition from a BCl3-H-2-CH4 gas mixture was achieved. An impinging-jet reactor was used to minimize the mass-transfer limitations on the reaction kinetics, which made a detailed kinetic investigation possible. Results of the XRD and XPS analyses showed that the solid product formed on the substrate is a rhombohedral B4C phase. Both dichloroborane and boron carbide formation rates were found to increase with an increase in the inlet molar fraction of BCl3. The formation rate of boron carbide increased with an increase in the inlet molar fraction of CH4. However, no effect on the formation rate of dichloroborane was observed with an increase in the inlet molar fraction of methane. The activation energy of the boron carbide formation reaction was ascertained to be 56.1 +/- 4.0 kJ/mol. The boron carbide formation reaction was proportional with the 0.34 +/- 0.055 power of the initial boron trichloride concentration and 0.64 +/- 0.084 power of the initial methane concentration. (c) 2006 American Institute of Chemical Engineers

Employing Imino-Bis-Propane Diol Functional Polymers for Boron Removal from Geothermal Waters via Polymer Enhanced Ultrafiltration

In this study, polymer enhanced ultrafiltration (PEUF) was used to remove boron from a geothermal water sample. The effect of co-ions such as chloride and sulfate on boron removal was investigated using previously synthesized poly (vinyl amino-N, N'-bis-propane diol) (GPVA) and its copolymers with DADMAC. The presence of co-anions and use of real waste water did not significantly reduce boron retentions and permeate fluxes. At optimum operating conditions 98% boron removal was achieved. It was demonstrated that 97% of complexation capacity of polymer can be recovered and reused by two-cycle decomplexation at pH 4

Novel boron specific copolymers with quaternary amine segments for efficient boron removal via PEUF

In this study, a copolymer, poly (vinyl amino-N, N'-bis-propane diol-co-DADMAC) (GPVA-co-DADMAC) was synthesized in three comonomer ratios (2%, 5% and 10%) and efficiently exploited for boron removal via polymer enhanced ultrafiltration (PEUF). Boron concentration could be reduced from 10 ppm down to 0.8 ppm by the employment of novel copolymer in continuous PEUF at pH 9 and boron-to-polymer mass ratio (loading) of 0.001. Polymer precipitation was not observed even after complexation with boron. Boron retention was found to be highly pH dependent and boron concentration dependent at constant loading. Hence, efficient polymer regeneration can be expected due to high pH and concentration dependency of boron complexation. Moreover, permeate flux was not affected by the polymer concentration in the conditions studied (polymer concentration <= 10 g/L; pressure drop: 2 bar). Dynamic and static light scattering measurements showed that gyration radius of the polymers rises by dilution or by increasing pH of the solutions. Furthermore, a two-step equilibrium model was correlated with the experimental boron retention data. Having high boron binding affinity, hydrolytic stability and efficiency in boron removal, the synthesized copolymers possessing DADMAC segments seemed to be attractive and useful for large scale water treatment with PEUF systems

Use of Specifically Tailored Chelating Polymers for Boron Removal from Aqueous Solutions by Polymer Enhanced Ultrafiltration

Two selective functional polychelatogens, namely hydroxyethylaminoglycerol functioned poly(glycidylmethacrylate (PNS) and Poly(4-Vinyl-1,3-dioxalan-2-one-co-vinyl acetate) (COP) were synthesized and utilized in polymer-enhanced ultrafiltration (PEUF) to remove boron from the aqueous solution. The effect of operating parameters on boron retention was investigated. PNS was synthesized in three molecular weights to observe the effect of molecular weight in borate retention. Increase in pH increased boron retention for all of the synthesized polymers. Decrease in loading resulted in an enhancement in retention values when COP, medium (PNSM) and the low molecular weight of PNS (PNSL) were used. No significant change was observed in the permeate flux with COP (41L/m2 center dot h), PNSL (48L/m2 center dot h) and PNSM (47L/m2 center dot h). However, a decrease in the loading led to a decrease in the permeate flux for high molecular weight PNS (PNSH). Conformational changes in the polymer structure were examined using dynamic and static light-scattering. Retention results for all of the polymers were found to be remarkably higher than the literature, when polyvinyl alcohol was used as the chelating agent. Satisfactory retention results were obtained using both PNSL (R: 54%) and PNSM (R: 57%), showing that PEUF can be employed effectively for borate removal using the specifically tailored polymers

Imino-bis-propane diol functional polymer for efficient boron removal from aqueous solutions via continuous PEUF process

Boron contamination is an environmentally serious problem especially due to its hazards on plants. In this work, newly synthesized poly (vinyl amino-N, N'-bis-propane diol) (GPVA) is presented as an excellent chelating polymer for boron removal. Boron concentration could be reduced from 10 ppm down to 0.4 ppm via total recycle Polymer Enhanced Ultrafiltration (PEUF). Experiments revealed that the polymer shows the highest PEUF boron rejections (96% at pH 9.0) reported so far, without precipitation in a wide concentration range. Detailed investigations such as effect of pH, loading (boron-to-polymer mass ratio) and polymer concentration showed that, the boron binding is highly pH dependent and increases with boron concentration at constant loading. Furthermore, permeate flux was found as nearly independent from polymer concentration up to 10 g/L at 200 kPa pressure drop. In addition, gyration radius of the polymer in solution increases while increasing pH and polymer concentration in the presence of boron as inferred from Dynamic and Static Light Scattering measurements. Regarding with high efficiency and hydrolytic stability of GPVA, its use in combination with PEUF would be of interest for large scale and long term use in boron removal