No abstract

Crosslinked poly(acrylic acid) (XPAA) made by copolymerization of acrylic acid and ethylene glycol dimethacrylate in bulk was further reacted with 80% ethoxylated polyethyleneimine, and the latter insolubilized by treatment with glutaraldehyde. The resulting composite sorbent, XPAA(EPEI.XG), containing carboxylic acid groups and weakly basic tertiary amine groups in close proximity in the same resin bead exhibited thermally regenerable desalination property, simulating the wellknown Sirotherm TM resins. For NaCl and MgCl 2 , the sorbent has saturation capacities of 0.796 and 0.839 meq/g (dry) sorbent, respectively, at 30 C but less than 0.1 meq/ g (dry) sorbent at 80-90 C. The equilibrium sorption data at 30 C fit well to both Langmuir and Freundlich isotherms for single-component sorption and to Butler-Ockrent and Jain-Snoeyink models for bicomponent sorption. Although the sorption of NaCl exhibits a plateau in the pH range of 4-5, that of MgCl 2 increases sharply above pH 4 because of additional sorption by cation exchange at the ionic sites formed at higher pH. The sorption rate data show characteristics of particle-diffusion controlled ionexchange process, yielding diffusivity values of 1.0-1.3 Â 10 À6 cm 2 /s for NaCl and 3.0-3.5 Â 10 À7 cm 2 /s for MgCl 2 , in the initial period at 30 C, with the diffusivity falling abruptly in both cases at higher conversions.

Interpenetrating polymer networks (IPNs) comprising weakly acidic and weakly basic cross-linked polymers, namely, poly(acrylic acid-co-ethyleneglycol dimethacrylate) (XPAA) and 80% ethoxylated polyethyleneimine (EPEI) cross-linked with glutaraldehyde, were prepared by the copolymerization of acrylic acid (AA) and ethyleneglycol dimethacrylate by a free-radical method, in the presence of calculated amounts of EPEI in methanol solution, followed by cross-linking with glutaraldehyde. The resulting IPNs, containing carboxylic acid groups and weakly basic tertiary amine groups in close proximity in the same resin bead, exhibited thermally regenerable desalination properties [e.g., sorption of salt at 30 °C and desorption at higher temperatures (80 °C)], simulating the behavior of the well-known Sirotherm resins. For NaCl and MgCl2, the maximum equilibrium sorption (∼0.5 mmol/g of dry resin in 0.1 M salt solution) was exhibited by an IPN with a carboxylic-to-amine (C/A) mole ratio in the range of 3−5. The equilibrium sorption at 30 °C for NaCl and MgCl2 on an IPN sorbent with a C/A mole ratio of 4.2 (referred to as Sirosorb) fitted well to both the Langmuir and Freundlich isotherms for single-component sorption and the Butler−Ockrent and Jain−Snoeyink models for bicomponent sorption. Containing both carboxylic and amine groups largely in a free state, Sirosorb exhibited buffer action over a wide range of feed solution pH values (3−8) to give nearly constant sorption of NaCl, although the sorption of MgCl2 increased with increasing pH because of additional sorption by ion exchange at the ionic sites formed by neutralization of the carboxylic acid groups. The sorption rate data showed characteristics of particle diffusion control with a NaCl and MgCl2 diffusivity ratio of 2:1, yielding diffusivity values of (2.5−3.9) × 10−7cm2/s for NaCl and (1.2−1.7) × 10−7cm2/s for MgCl2 in the initial period at 30 °C, with the diffusivity falling abruptly in both cases at higher conversion. Continuous column operation performed with Sirosorb showed that the quantity of potable water with a NaCl content of less than 1500 mg/L that can be produced is about 4 times the weight (dry) of the resin, when the influent brackish water has a NaCl content of 3000 mg/L. The used resin was regenerated with 1 M NaCl solution at 90 °C and used repeatedly with no apparent loss of capacity, as demonstrated in the present work for up to 10 cycles of operation.

ABSTRACT:A commercial acrylic fiber with 92% (w/w) acrylonitrile content was partially hydrolyzed converting a fraction of the nitrile (OCN) groups to carboxylic acid (OCOOH) groups, to coat the fiber with polyethylenimine (PEI) resin, which was then crosslinked with glutaraldehyde and further quaternized with ethyl chloroacetate to produce a novel strong-base anionic exchanger in the form of fiber. Designated as PAN(QPEI.XG)(Cl Ϫ ), the fibrous sorbent was compared with a commercial bead-form resin Amberlite IRA-458(Cl Ϫ ) in respect of sorption capacity, selectivity, and kinetics for removal of silver thiosulfate complexes from aqueous solutions. Though the saturation level of [Ag(S 2 O 3 ) 2 ] 3Ϫ on PAN(QPEI.XG)(Cl Ϫ ) is considerably less than that on IRA-458(Cl Ϫ ), the gel-coated fibrous sorbent exhibits, as compared to the bead-form sorbent, a significantly higher sorption selectivity for the silver thiosulfate complex in the presence of excess of other anions such as S 2 O 3 2Ϫ , SO 4 2Ϫ , and Cl Ϫ , and a remarkably faster rate of both sorption and stripping. The initial uptake of the sorbate by the fibrous sorbent is nearly instantaneous, reaching up to ϳ80% of the saturation capacity within 10 s, as compared to only ϳ12% on the bead-form sorbent. The high initial rate of uptake fits a shell-core kinetic model for sorption on fiber of cylindrical geometry. With 4M HCl, the stripping of the sorbed silver complex from the fibrous sorbent is clean and nearly instantaneous, while, in contrast, a much slower rate of stripping on the bead-form sorbent leads to its fouling due to a slow decomposition of the silver thiosulfate complex in the acidic medium.

Purpose: The purpose of this study was to investigate how knowledge flow and productivity affect the absorptive capacity of target firms in emerging markets.Design/methodology/approach: We used self-administered questionnaires to measure absorptive capacity, knowledge flow and productivity constructs. The sample comprised individuals who were employees of firms that completed acquisitions between 2015 and 2017. The acquisitions were publicly announced and the target firms were all in emerging markets.Findings/results: Firstly, our results confirmed the multidimensional nature of absorptive capacity. Secondly, we found a positive correlation between a target firm’s knowledge flow and productivity and its absorptive capacity. Thirdly, our results indicated that knowledge flow and operational processes will support the introduction and integration of external knowledge into a target firm. Therefore, understanding the absorptive capacity of target firms is central to the ability of new and existing knowledge to be assimilated.Practical implications: The realisation of the strategic intent of an acquisition is dependent on effective knowledge flow, supported by efficient communication and operational processes. The target firm’s absorptive capacity is, therefore, a key consideration for acquiring firms. Understanding this will be useful for firms to consider acquisitions of target firms in emerging markets and could potentially enhance their chances of success.Originality/value: This study contributes to the limited body of research on emerging market merger and acquisition activity. It responds to the call for further research to be conducted on emerging markets and the role of absorptive capacity in realising the strategic intent of acquisitions.