Nalan Kabay

REMOVAL OF BORON FROM WASTEWATER OF GEOTHERMAL POWER PLANT BY SELECTIVE ION-EXCHANGE RESINS. II. COLUMN SORPTION-ELUTION STUDIES

Column sorption–elution studies for boron removal were performed using N-glucamine-type chelating ion-exchange resins Diaion CRB 02 Purolite S 108. The breakthrough curves were obtained as a function of resin type and feed flow rate. Boron was effectively removed from the wastewater of Kizildere, Turkey, geothermal power plant by passing it through the resins Diaion CRB 02 and Purolite S 108 at a space velocity of 25 bed volumes per hour. The boron on the resins was quantitatively eluted with 0.25 M H2SO4 solution. The resin Diaion CRB 02 was used to study the recycle use of resin for boron removal from the wastewater of Kizildere geothermal power plant. The capacity of Diaion CRB 02 remained constant after three sorption–elution–washing–regeneration cycles.

Removal of Cr(VI) by solvent impregnated resins (SIR) containing aliquat 336

Abstract Solvent impregnated resins (SIR) have been prepared by a wet-impregnation technique using two different polymer matrices, Diaion HP-20 and HP-2MG. Diaion HP-20 possesses a hydrophobic styrene–divinylbenzene polymeric structure whereas HP-2MG is a hydrophilic methacrylic based polymer. Aliquat 336 was employed as the extractant and acetone as the solvent for impregnation. Batch sorption studies have shown that solvent impregnated resins containing Aliquat 336 can be effectively used for the removal of hexavalent chromium from aqueous solutions. The Langmuir adsorption isotherm gave a satisfactory fit of the equilibrium data. A kinetic study has been performed for SIR at two different concentrations of Cr(VI) (2×10 −4 and 4×10 −4 M). A finite-bath diffusion-control model with changing bulk concentration was used for sorption of Cr(VI) by SIR. Increasing the impregnation ratio from 0.5 to 1.0 (g Aliquat 336/g polymer adsorbent) increased the breakthrough capacity in a column-mode sorption study. The Cr(VI) bound by the SIR has been quantitatively desorbed using 0.1 M NaOH–0.1 M NaCl mixture.

Removal of bisphenol A (BPA) from water by various nanofiltration (NF) and reverse osmosis (RO) membranes

The removal of an endocrine disrupting compound, bisphenol A (BPA), from model solutions by selected nanofiltration (NF) and reverse osmosis (RO) membranes was studied. The commercially available membranes NF 90, NF 270, XLE BWRO, BW 30 (Dow FilmTech), CE BWRO and AD SWRO (GE Osmonics) were used to compare their performances for BPA removal. The water permeability coefficients, rejection of BPA and permeate flux values were calculated for all membranes used. No significant changes in their BPA removal were observed for all tight polyamide based NF and RO membranes tested except for loose NF 270 membrane. The polyamide based membranes exhibited much better performance than cellulose acetate membrane for BPA removal. Almost a complete rejection (≥ 98%) for BPA was obtained with three polyamide based RO membranes (BW 30, XLE BWRO and AD SWRO). But cellulose acetate based CE BWRO membrane offered a low and variable (10-40%) rejection for BPA.

Removal of calcium and magnesium hardness by electrodialysis

The separation performances of divalent ions (Ca2+ and Mg2+) by electrodialysis (ED) were compared using a constant voltage mode of operation. For the batch tests, TS-1-10 ED equipment was employed. During the experimental studies, the effects of electrical potential applied and flow rate of streams on the separation performance of each cation have been monitored by measuring the outlet concentrations of the dilute stream. The operation time was short when a high potential was applied. On the other hand, the effect of flow rate on separation performance was not so apparent. Specific power consumption increased with an increase in potential applied, although it was not sensitive to the change in flow rate.

Removal of Fluoride from Water by Metal Ions (Al3+, La3+ and ZrO2+) Loaded Natural Zeolite

Abstract In this study, the ion exchange of metal ions (Al3+, La3+ and ZrO2+) on modified zeolites was carried out using batch method. Fluoride removal from water using Al3+‐, La3+‐ and ZrO2+‐ exchanged zeolite was subsequently investigated to evaluate the fluoride sorption characteristics of the sorbents. Natural zeolite samples (<45 µm) were pre‐conditioned with HNO3 solution (ZEO‐1), NaNO3 solution (ZEO‐2), and deionized water (ZEO‐3) before loading Al3+, La3+, and ZrO2+ on zeolite. ZEO‐1 type zeolite had a higher capacity than ZEO‐2 and ZEO‐3 type zeolites. Metal exchange capacities are 0.233, 0.089, 0.090 mmol/g for ZrO2+‐, La3+‐, and Al3+‐ exchanged zeolite (ZEO‐1), respectively. Equilibrium isotherms fitted well to Langmuir and Freundlich models. Percent removal of fluoride from aqueous solution containing 2.5 mg F/L was 94% using metal loaded zeolite (ZEO‐1 type) at an adsorbent concentration of 6.00 g/L.

Extraction of Cd(II) and Cu(II) from phosphoric acid solutions by solvent-impregnated resins (SIR) containing cyanex 302

Solvent-impregnated resins (SIR) containing Cyanex 302 (bis [2,4,4-trimethylpentyl] monothiophosphinic acid) have been prepared using Amberlite XAD-2, XAD-4, XAD-7 and XAD-8 as polymeric support. These prepared SIR have been used for the extraction of Cd(II) and Cu(II) from phosphoric acid solutions. The effect of phosphoric acid concentration on Cd(II) uptake has been investigated by batch extraction method. Columnar extractions of Cd(II) and Cu(II) from 40% H3PO4 have been performed using XAD-7 resin impregnated with Cyanex 302. The resin exhibited similar column sorption behaviour for both Cd(II) and Cu(II). The elution of both Cd(II) and Cu(II) from SIR has been achieved with 4 M HCl solution. The elution of Cd(II) occurred sharply but with a long tail-off and furthermore the elution of Cu(II) was slow.

Chelating Polymers for Recovery of Uranium from Seawater

Abstract Despite the low concentration of uranium in seawater (3.3 ppb), a special emphasis has been placed on its recovery. Although the concentration is low, it has been estimated that the worlds oceans contain about 4 × 109 tons of uranium—theoretically an unlimited supply of nuclear fuel. Adsorption has been considered to be a technically feasible procedure for a uranium recovery process with regard to economic and environmental impacts. The present paper restricts its coverage to those applications using chelating polymeric resins containing amidoxime groups as the most promising adsorbent. ∗Dedicated to Prof. Iwao Tabushi for his endeavors in the field of “recovery of uranium from seawater.”

Kinetic Behavior of Lightly Crosslinked Chelating Resins Containing Amidoxime Groups for Batchwise Adsorption of UO2 2

Abstract Lightly crosslinked poly(acrylonitrile-co-divinylbenzene) beads (RN-5) have been synthesized by suspension polymerization. The use of dichloroethane and chloroform as a porogen produced lightly crosslinked copolymer beads having highly porous structures. The chelating resins containing amidoxime groups (RNH-5) have been prepared by the reaction of copolymer beads with NH2OH in MeOH. The resulting chelating resins have been used in the batchwise adsorption of UO2 2+ from nitrate solutions containing 0.01 mol·dm−3 UO2 2+ at pH 3.25. In order to get some measure of the relative performance of each resin in kinetic terms, the extraction of UO2 2+ was monitored with time and some adsorption profiles were obtained. An increase in porogen content resulted in a marked increase in the batchwise adsorption of UO2 2+. Alkaline treatment allowed a high swelling and hence rapid accessibility of UO2 2+ to the ligands. Even after 30 minutes, the alkali-treated resins were 50% loaded.

Cost comparison and efficiency modeling in the electrodialysis of brine

Abstract The separation performance of Na + ions from NaCl solution has been investigated by electrodialysis at constant voltage mode of operation. TS-1-10 electrodialysis equipment (Tokuyama) modified with rotameters was employed in experimental studies. During an unsteady-state run of the ED system, both inlet and outlet concentrations of both concentrate and dilute streams were measured at time intervals of 5 min until the current drops to less than 0.01 A. The effects of parameters such as electrical potential applied (DC) and flow rate of streams on the performance of separation were observed. The efficiencies of each run were evaluated as specific power consumption with the electrical energy consumed only in stack. Current efficiency was represented as a function of flow rate, which is based upon the mass transfer coefficient. The model proposed was in very good agreement at all flow rates at low potential applied, however, at the highest flow rate at other potentials, small deviations were found.

Demineralization by electrodialysis (ED) — separation performance and cost comparison for monovalent salts

Abstract The separation performance of K+ ions from KCl solution has been investigated by electrodialysis at constant voltage mode of operation as a function of flow rate and voltage scanned. TS-1-10 model electrodialysis equipment (Tokuyama) modified with rotameters was employed in experimental runs. The efficiencies of each unsteady state run were evaluated as specific power consumption with the electrical energy consumed only in stack. The separation performance of K+ ions was compared with that of Na+ ions.