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Ferrous sulfate heptahydrate FeSO4 7H(2)O is a major waste produced in titanium dioxide industry by the sulfate process and has caused heavy environmental problem. A new green process for the treatment of FeSO4 7H(2)O was proposed to make use of iron source and recycle sulfate source as H2SO4. It was found that by adding concentrated HCl to the FeSO4 solution, FeCl2 4H(2)O was crystallized out, which was subsequently calcined to produce Fe2O3 and HCl. Concentrated H2SO4 solution (about 65 wt %) was obtained by evaporating the FeCl2 4H(2)O-saturated filtrate. To facilitate the process development and design, the solubilities of FeCl2 4H(2)O in HCl, H2SO4, and HCl+H2SO4 solutions were measured and the experimental data were regressed with both the mixed-solvent electrolyte model and the electrolyte NRTL model. On the basis of the prediction of the optimum conditions for the crystallization of FeCl2 4H(2)O, material balance of the new process was calculated. FeCl2 4H(2)O and Fe2O3 were obtained from a laboratory-scale test with about 70% recovery of ferrous source for a single cycle, indicating the feasibility of the process. (c) 2017 American Institute of Chemical Engineers AIChE J, 63: 4549-4563, 2017

The structural stability of electrode materials and their compatibility with electrolytes are the important properties for ion-intercalative electrochemical energy-storage devices. In the present work, we employed zinc hexacyanoferrates (ZnHCFs), which occurs as cubic or rhombic phases, as the probe to tailor the mechanism of capacity decay upon electrochemical cycling and the corresponding mitigating strategy. Capacity fading results from the loss of active materials, which is highly correlated to the phase states; this has been identified for both phases, where the cubic phase is demonstrated to be the dominant source of ZnHCF dissolution. In 1 m KNO3 electrolyte, rhombic ZnHCF behaves evidently more stable than the cubic phase for long-term galvanostatic charge/discharge cycling. Even when simply immersed in an aqueous environment, the rhombic–cubic phase transition can spontaneously occur, which, in particular, can be accelerated considerably by electrochemical redox processes in the potential window of 0.8–1.1 V. Utilizing the common-ion effect, specifically by incorporating ZnII into aqueous electrolytes, could considerably enhance the capacity retention of ZnHCF. Our results suggest that, if electrode materials are soluble at certain electrochemical stages, introducing electrochemically inert common ions into the electrolyte should be an efficient approach to improve the electrode–electrolyte compatibility for pursuing enhanced cycling performances.

Based on chemical modeling of phase equilibria for the NH4Cl-MgCl2-AlCl3-H2O system, a practical approach to produce Mg-Al spinel (MgAl2O4) (widely used as refractory brick, supports in catalysts, and inert material for oxygen carriers) is proposed and proven feasible. This novel process includes coprecipitation of Mg4Al2(OH)14 center dot 3H2O from the NH3-MgCl2-AlCl3-H2O system; calcination of Mg4Al2(OH)14 center dot 3H2O to obtain Mg-Al spinel and recovery of NH4Cl from NH4Cl-rich solutions by feeding MgCl2-AlCl3. A MSMPR reactor was applied to investigate the effect of temperature, feed concentration, and NH4Cl addition on coprecipitation of precursor Mg4Al2(OH)14 center dot 3H2O from MgCl2-AlCl3 solutions with Mg/Al ratio = 2 through gradual addition of NH4OH. The phase equilibria of the NH4Cl-MgCl2-AlCl3-H2O system were determined over the temperature range 283.2 to 363.2 K using dynamic method. The experimental solubilities were regressed to obtain new Bromley-Zemaitis model parameters. These newly obtained parameters were verified by predicting the quaternary system. A chemical model for the NH4Cl-MgCl2-AlCl3-H2O system has been established with the OLI platform. All the results generated from this study will provide the theoretical basis for Mg-Al spinel production. The high quality Mg-Al spinel was prepared by calcination of precursor from 773.2 to 1273.2 K, and the NH4Cl was successfully recovered through the common ion effect of MgCl2-AlCl3 addition. (c) 2012 American Institute of Chemical Engineers AIChE J, 59: 18551867, 2013

Phosphate esters of two butanol isomers were synthesized by esterification of n-butanol and isobutanol with phosphorus pentoxide. The surface activity and penetrability of the esters were analyzed by way of surface chemistry and canvas disc wetting tests in different alkaline solutions. The surface tension of the butanol phosphate esters and their sodium salts was found to decrease with increasing alkaline concentration up to 250 g/L NaOH. Furthermore, the products exhibited a good surface activity with proper penetrability even in highly alkaline solutions. The stable surface activity of the esters in concentrated alkali lye interpreted by the adsorption of the molecule from solution owing to the common ion effect.

The addition of lithium chloride (LiCl) to a solution of polystyryllithium (PStLi) in tetrahydropyran (THP) reduces the rate of propagation of PStLi at a low concentration of the latter but accelerates it at higher concentrations of PStLi. Moreover, the addition of LiCl, which is dimeric in ethereal solutions, increases the conductance of PStLi solutions in tetrahydrofuran (THF) and THP to a much greater extent than expected from the separate conductances of PStLi and LiCl, which is itself even less dissociated than PStLi. These phenomena are fully explained by the dual action of LiCl. Below a certain concentration of PStLi, the dissociation, not of LiCl as such, as claimed before, but of its solvated dimer into free Li + ions and ClLiCl triple ions provides Li + ions that repress the ionic dissociation of PStLi by a common ion effect. This, in turn, diminishes the concentration of free polystyryl anions, which are the dominating species responsible for the propagation of PStLi, resulting in retardation. However, at higher concentrations of PStLi, Li' ions produced by its dissociation are scavenged by the scavenging action of LiCI dimers, producing quintuple cations. This reduces the concentration of free Li + ions and, therefore, increases the concentration of the reactive free polystyryl anions, resulting in an acceleration of the propagation.

The phase separation of polycarboxylates in the presence of high concentrations of 1 :1 and 1 :2 electrolytes has been studied. Sodium polyacrylate remained in one phase at concentrations as high as 5 mol dm -3 sodium chloride whereas the fully ionised copolymer of acrylic acid and maleic anhydride (PAMA) phase separated at less than 1.0 mol dm -3 . PAMA phase separated at polymer and electrolyte concentrations that had constant sodium ion activity, showing that the separation was essentially due to the common ion effect. Potassium salts did not produce any separation. In contrast to the 1 :1 electrolytes, addition of 1 : 2 electrolytes (Na 2 SO 4 and Na 2 CO 3 ) produced no separation, indeed caused a two-phase system, to revert to one phase. This initially surprising result was attributed to the increasing negative adsorption of the SO 4 2- or CO 3 2- from the polyion as the latter's concentration increased. This negative adsorption was expected to be greater for divalent than monovalent anions.

Salt formation is the most common and effective method of increasing solubility and dissolution rates of acidic and basic drugs. In this article, physicochemical principles of salt solubility are presented, with special reference to the influence of pH-solubility profiles of acidic and basic drugs on salt formation and dissolution. Non-ideality of salt solubility due to self-association in solution is also discussed. Whether certain acidic or basic drugs would form salts and, if salts are formed, how easily they would dissociate back into their free acid or base forms depend on interrelationships of several factors, such as S0 (intrinsic solubility), pH, pKa, Ksp (solubility product) and pHmax (pH of maximum solubility). The interrelationships of these factors are elaborated and their influence on salt screening and the selection of optimal salt forms for development are discussed. Factors influencing salt dissolution under various pH conditions, and especially in reactive media and in presence of excess common ions, are discussed, with practical reference to the development of solid dosage forms.

The results of adiabatic compressibility measurement for the 100% neutralized sodium and hydrochloride salts of three copolymers of acrylic acid and N-dimethylaminoethyl methacrylate, namely, AA-DAM 58, AA-DAM 43, and AA-DAM 33, are discussed. Similar to three unneutralized amphoteric polyelectrolytes, the ϕK2 and ϕV2's for these salts are found to be concentration independent. Since in the former both anionic and cationic groups are present, fully neutralized sodium salts and hydrochloride salts of these polyelectrolytes are expected to show a decrease in ϕK2i0 and ϕV2i0 values due to maximum electrostriction. In fact, in case of AA-DAM 58 with excess amino group in the chain (58%), the experimentally obtained values are found to be −9.6 × 10−4 cc/bar/mole and 159.6 cc/mole, and −3.3 × 10−4 cc/bar/mole and 164.4 cc/mole for sodium and hydrochloride salts, respectively, which corresponds to a decrease of 7.1 × 10−4 cc/bar/mole and 4.9 cc/mole for the sodium salt and 0.8 × 10−4 cc/bar/mole and 0.1 cc/mole for the hydrochloride salt. In contrast, the hydrochloride salt of AA-DAM 43 shows an increase of 6.2 × 10−4 cc/bar/mole and 2.2 cc/mole, respectively, while in case of AA-DAM 33, both the hydrochloride salt (56.2 × 10−4 cc/bar/mole and 24.7 cc/mole) and the sodium salt (6.2 × 10−4 cc/bar/mole and 6.2 cc/mole) show an increase. This increase has been ascribed to suppression of dissociation of carboxyl groups by the hydrochloric acid (common ion effect) added for neutralization. However, in all the three amphoteric copolymers, when neutralized with NaOH solution or HCI acid, the viscosity increases over that of the unneutralized copolymer.

Spiro[2,4]hepta-4,6-diene, a derivative of cyclopentadiene, was polymerized at −76°C with various triphenylmethyl salts as initiator. The polymer consists only of the 1,2- and 1,4-addition structures, and their contents can be determined by the relative area of the olefin proton peaks. The polymer structure changed characteristically with the polymerization conditions. The content of 1,4-structure decreased with increasing polarity of the medium from 45–70 in toluene to 25–30% in 7:3 CH2Cl2–CH3CN. In 1:1 CH2Cl2–toluene, the 1,4-structure content decreased from 70% to 40% with increasing radii of counteranions. These results were interpreted according to the model of the cationic propagation proposed earlier, as arising from the different tightness of the propagating ion pair. In the case of pentacoordinate counteranions, in particular SnCl5−, the 1,4-structure content was greater than expected from the anion size alone and decreased with increasing initiator concentrations, in contrast with the behavior of the other tetra- and hexacoordinate anions. This was attributed to the possibly facile aggregation of the pentacoordinate anion. However, the common ion effect was not observed.

Neighboring group participation in the solvolytic reactions of a series of ω-(2-tetx-a-hydrofuran)alkyl p - bromobenzenesulfonate esters has been investigated. Anchimeric assistance to solvolysis is most pronounced in the case of 3-(2-tetrahydrofuran)propyl p-bromobenzenesulfonate where a 1-oxabicyclo[3.3.0]octane cation can form. A “special salt effect” and an “induced common ion effect” were observed in the acetolysis of this ester. It appears that the tetrahydrofuran ring is about twice as effective as the methoxyl group in neighboring group participation.

2-Chloromethyl-1-methylimidazole undergoes a pH-dependent aqueous hydrolysis with the neutral substrate being the reactive species, and the imidazole-protonated form (pKa = 5.7) unreactive. Addition of sodium chloride retards the hydrolysis, evidence that there is a free carbenium ion intermediate (the common ion effect). The rate constant ratio Kcl/Kw for the reactions of this cation with the added chloride and with the solvent is 7.4 M−1. Further evidence for a free cation is the observation of the 2-azidomethyl product when the hydrolysis is carried out with sodium azide present, but with no change in the rate constant. The Kaz/Kw ratio as determined by product analysis is 1.1 × 102 M−1 With the assumption that kaz represents a diffusion-controlled reaction and has a value of 7 × 109 M−1 s−1, the rate constant kw for the reaction of the cation with solvent is 6 × 107 s−1. A comparison with azide–water selectivity ratios reported for other cations shows that the imidazole-stabilized primary cation of th...