Removal of toxic aqueous ions using amorphous AlPO4

Aluminium phosphate (AlPO₄) was characterized using X-ray diffractometry (XRD), Fourier Transform infrared (FTIR), point of zero charge (PZC) and dissolution studies. XRD showed the sample to be amorphous, FTIR confirmed the presence of OH groups on the surface and PZC was determined at pH 3.45. The dissolution study illustrated a decrease in dissolution with an increase in the pH. Potentiometric titration data were fit to the Gaines–Thomas equation, which showed that AlPO₄ is a weakly acidic ion exchanger. Sorption studies were carried out at pH 4–6 and temperatures 293–323 K. The uptake of metal ions was observed to increase with an increase in the pH and temperature. The surface selectivity towards metal ions was found in the order Pb²⁺> Cu²⁺> Cd²⁺. Sorption data were fit to the new equation derived from the proposed mechanism for metal ion uptake. Various parameters such as stoichiometry of the surface H⁺ ion release, equilibrium constant, standard enthalpy, entropy and free energy changes were evaluated from the plots. The values of all these parameters were found to be closely related to the values reported in the literature.     

Miscibility enhancement of poly(vinyl chloride)/polystyrene blend: Application to membrane separation of benzene from benzene/cyclohexane mixture by pervaporation

In order to improve the miscibility of poly(vinyl chloride)/polystyrene (PVC/PS) system and to use the prepared material as a membrane to separate benzene from benzene/cyclohexane mixture by pervaporation technique, two poly(styrene-co-N-vinylpyrrolidone) (PSVP) copolymers containing 6.67 and 13.55 mol% of N-vinylpyrrolidone (N-VP) contents were synthesized through a radical polymerization. A comparative study of the miscibility of the PVC/PSVP blends with different compositions was carried out using differential scanning calorimetry, viscosimetry and Fourier transform infrared spectroscopy methods in which the interaction parameters between the two components were widely investigated. To improve the pervaporative flux of PVC membrane to separate benzene from benzene/cyclohexane mixture, a preliminary test of swelling and sorption was performed on PVC/PSVP7 membranes using an azeotropic benzene/cyclohexane mixture. It was revealed that the PVC/PSVP7 membrane containing 10 wt% of PSVP7 showed the best performance and the diffusion behaviour of this mixture through PVC and PVC/PCVP7 membranes has a Fickian behaviour. The pervaporation parameters of this membrane support those of the swelling and selective sorption data and reveal that this membrane could enhance the total flux without significantly affecting its selectivity to benzene.     

Preparation of a novel chelating resin bearing amidinothiourea moieties and its removal properties for Hg(II) ions in aqueous solution

A novel chelating resin bearing amidinothiourea (ADTU) moieties was prepared by chloroethyl crosslinked polystyrene (CMPS) with ADTU in the presence of a phase transfer catalyst. Fourier transform infrared spectra (FT-IR) and scanning electron microscopy (SEM) were used to characterized the resulting chelating resin. The saturated adsorption capacity of Hg(II) ions estimated from the Langmuir model was up to 1215 mg g^?1at 313 K. Furthermore, the resin was able to selectively separate Hg(II) from multicomponent solutions with Cd(II), Co(II), Cu(II), Zn(II), Mg(II) and Pb(II). The desorption process showed the mercury recovery reached to 99.2% under eluting condition of 1 M HCl + 8% thiourea.     

Sorption of ruthenium by dipropylmethyl-2-(N,N-diisobutyl) acetamidoammonium iodide impregnated Amberlite XAD-4 resin from nitric acid medium

Dipropylmethyl-2-(N,N-diisobutyl)acetamidoammonium iodide has been impregnated on Amberlite XAD-4 resin and investigated for sorption of Ru from nitric acid medium. Equilibrium sorption data for Ru uptake were represented well by the Langmuir isotherm equation (R² = 0.98) compared to Freundlich isotherm equation (R² = 0.86). The maximum monolayer coverage (Q₀) value of 6.25 mg/g as obtained from Langmuir isotherm was close to the experimental value (5.63 mg/g). The heterogeneity parameter (1/n) = 0.37 obtained from the slope of Freundlich isotherm indicates slight heterogeneity in sorption process. Aqueous solutions of 5% ammonia or 10% sodium hydroxide were found suitable for desorption. The method can be applied for separation of Ru from acidic waste solutions.     

RIP法吸附设备级间空气提升器的效率和防堵研究

对RIP法吸附设备级间空气提升器的效率和防堵进行了研究。结果表明,空气提升器的提升速度与空气消耗量、沉没系数、提升器截面积(提升器结构)有关;提升器的效率是总提升速度、沉没系数、提升器截面积的函数。为保证吸附剂的最大提升速度,应使提升器工作于最佳状态。通过专门的结构设计或相应的工作制度,进气嘴和提升管堵塞可以得到很好解决。     

Equilibrium moisture content and heat of desorption of saffron

The equilibrium moisture contents of saffron (Crocus sativus L.) stigmas were determined experimentally using the standard gravimetric method at temperatures 30, 45 and 60 °C and water activity ranging from 11% to 83%. The sorption isotherm curves of saffron were sigmoidal in shape and decreased with increased temperature at constant relative humidity. Five selected isotherm models GAB, modified Henderson, modified Chung‐Pfost, modified Halsaey and modified Oswin were tested to fit the experimental isotherm data. Modified Oswin and modified Henderson models were found acceptable for predicting desorption moisture isotherms and fitting to the experimental data, respectively. The isosteric heats of desorption, determined from equilibrium data using the Clausius‐Clapeyron equation, were found to be a function of moisture content. The net isosteric heat of desorption of saffron varied between 1.38 and 5.38 kJ mol^?1 at moisture content varying between 2% and 20% (d.b).     

Modeling water sorption dynamics of cellular solid food systems using free volume theory

Water sorption and dynamical properties of bread crust were studied using gravimetric sorption experiments. Water uptake and loss were measured while relative humidity (RH) was step-wise in- or decreased. Experimental results were compared with Fickian diffusion models and empirical models like the exponential and power-law model. From comparison of experimental sorption curves and the power-law model for short times it followed for all bread crust that the diffusional coefficient n is close to one. It turned out that this is not due to so-called case II diffusion and water transport that is limited by relaxation of the solid material but due to the fact that RH did not instantaneously but gradually increased to the set value.Sorption curves of isotherm experiments could be best described by the Fickian diffusion model for low RH and by the exponential model for large RH. Transport rates depend on moisture content and show a maximum around RH = 0.7, corresponding to a water mass fraction ω₁ = 0.12. Diffusion rates could be well described by free volume theory up to the maximum, but this theory could not explain the strong decrease at higher ω₁. Indications for a local glass-rubber transition at room temperature were found near a water mass fraction ω₁ ≈ 0.09. This corresponds very well to the start of the crisp–non-crisp transition as measured by a sensory panel, but not to the glass-rubber transition at ω₁ ≈ 0.12 as measured by other techniques like Differential Scanning Calorimetry. So it seems that more than one glass-rubber like transitions may be important to describe the properties of heterogeneous cellular food systems.     

Graft Copolymers of Acrylonitrile onto Dextrin for Use in Separation Technologies

The use of polymers in enrichment and separation technologies has attracted a lot of interest in recent times. To develop low-cost and environmentally friendly technologies for the removal of metal ions from water systems, graft copolymers based on dextrin were synthesized by grafting poly(acrylonitrile) onto it. The optimum grafting conditions were evaluated for grafting by varying the nature and amount of solvent, changes in concentration of monomer and initiator, reaction time and temperature. Graft copolymers were further functionalized by partial hydrolysis, and were characterized by water uptake, FTIR, SEM and elemental analysis. Sorption of Fe²⁺ and Cr⁶⁺ ions on graft copolymers were investigated as a function of percent grafting, change in metal ion concentration, temperature and pH, to define their end-uses in separation technologies.     

Moisture sorption and thermodynamic properties of cassava starch and soy protein concentrate based edible films

Moisture sorption isotherms and thermodynamic properties of cassava starch and soy protein concentrate–based edible films were investigated. Equilibrium moisture content was determined at various temperatures (10, 20, 30 and 40 °C) and relative humidities (17–83%) using gravimetric method, and the results were analysed using four sorption isotherm models. The equilibrium moisture of edible films (both adsorption and desorption modes) decreased with soy protein concentrate addition and temperature at constant water activity. The monolayer moisture content values of cassava starch–soy protein concentrate edible films decreased with increase in temperature and soy protein level. GAB and Oswin models (%RMS ≤10) best described the isotherms of the biofilms with the monolayer moisture contents, isosteric enthalpy and entropy higher for adsorption with significant kinetic compensations. The moisture sorption and thermodynamic properties of cassava starch–soy protein concentrate edible films showed that they are suitable for packaging applications.