PHYSICAL CHEMISTRY OF ADSORPTION OF COPPER,NICKEL AND COBALT ON LIGNITE FROM AMMONIACAL SOLUTIONS

The adsorption of Me(metal),NH_3 and CO_2 on lignite from ammoniacal solution containing metallicions such as Cu,Ni,and Co was investigated.Preliminary mechanism studied revealed that active carboxyland phenolic groups of humic acid in lignite as well as surface adsorption were involved.The rate of ap-proach to adsorption equilibrium on lignite was NH_3>Ni>Co>Cu andthe adsorption on lignite is Cu>Co>Ni>NH_3.The order of selective elution was NH_3>>Ni,Co>Cu.All metals were fully stripped and NH,could only be recovered partially.NH_3 adsorbed on lignite fron metal-ammoniacal solution is easily lost by volatilization,only a smallfraction remaining on lignite at a temperature of 120℃.CO_2 adsorbed physically in nature from ammonia-cal solution with a capacity of less then one percent was observed under the practical conditions generallyin hydrometallurgy.     

β-CAROTENE ADSORPTION ONTO MESOPOROUS CARBON-COATED MONOLITH COLUMN: DYNAMIC STUDIES

β-carotene adsorption dynamics from isopropyl alcohol (IPA) solution onto a mesoporous carbon-coated monolith (MCCM) column was studied. Kinetics and mass transfer parameters were modeled. Thomas and Adams-Bohart models were applied to the experimental data obtained from dynamic studies. The effects of bed depth, flow rate, and influent concentration on breakthrough curves and adsorption capacity were investigated. The results showed that β-carotene equilibrium uptake increased with decreasing flow rate and increasing influent concentration. The optimum adsorption capacity (1.37 mg/g) was achieved at 20 mg/L initial β-carotene concentration, 47.5 cm bed height, and 1.0 mL/min flow rate. The time to attain breakthrough point decreased, while a sharp breakthrough curve was observed with increase in flow rate and influent concentration and a decrease in bed height.     

EQUILIBRIUM AND KINETIC STUDIES FOR THE ADSORPTION OF MN(II) AND CO(II) FROM AQUEOUS MEDIUM USING AGAR–AGAR AS SORBENT

An extensive increase in industrial activities and environmental accidents in recent years have greatly contributed to increasing metal pollution in water resources, thereby causing threats to terrestrial as well as aquatic life. The toxicity of metal pollution is slow and long lasting, as these metal ions are nonbiodegradable. The most appropriate solution for controlling the biogeochemistry of metal contaminants to produce high-quality treated effluents from polluted wastewaters is sorption technique. Agar–agar, a readily available seaweed, was used as sorbent for the removal of Mn(II) and Co(II) from aqueous media. Batch experiments were performed to study adsorption as a function of process parameters: sorption time, initial pH, concentration of sorbate and sorbent. The Freundlich model fitted best with the experimental equilibrium data between the two adsorption isotherm models tested. The kinetic data correlated well with the Lagergren pseudo-second-order kinetic model for the sorption of both Mn(II) and Co(II) using agar–agar. Adsorbed metal ions were quantitatively recovered from the spent adsorbent using 5.0 mol L^?1 HCl. The efficiency of agar–agar for decontaminating Mn(II) and Co(II) from electroplating effluent has also been evaluated. The results proved agar–agar to be a favorable adsorbent to remove and recover Mn(II) and Co(II) from waste effluent for further use in diversified industrial applications.     

ADSORPTION EQUILIBRIUM OF ETHYLENE-CARBON DIOXIDE MIXTURE ON ZEOLITE ZSM5 AND ITS CORRELATION

Binary gas mixture adsorption equilibrium data for the ethylene-carbon dioxide system were obtained for cation exchanged forms of ZSM5 (Li~ , Na~ , K~ , Rb~ , Mg~( 2), Ca~( 2), Sr~( 2), and Ba~( 2)) for the gas phase CO_2 mole fracion of 0.766 at 308K and 101. 3kPa. The experimental adsorption phase diagrams were obtained for CO_2-C_2H_4 on NaZSM5 and MgZSM5. Single component adsorption isotherms for CO_2 and C_2H_4 were also obtained for these two zeolites. The single component data were used to obtain parameters derived in the vacancy solution model (VSM) and the statistical thermodynamic model(STM). These parameters were, in turn, used to predict binary mixture isotherms for these two zeolites. The agreement between experimental data and predicted value is generally good.     

VAPOR-LIQUID EQUILIBRIUM FOR TERNARY MIXTURES OF BENZENE,TOLUENE,AND p-XYLENE

Vapor-liquid equilibrium composition and temperature were measured for binary andternary mixtures of benzene,toluene and p-xylene at 101.33 kPa The equilibrium cell of Boubliketal.was modified for the present study.The experimental vapor-liquid equilibrium data were corre-lated with the Wilson equation.     

DETERMINATION,CORRELATION AND PREDICTION OF LIQUID-LIQUID EQUILIBRIUM DATA OF n-BUTYL ALCOHOL-WATER-BUTYL ACETATE TERNARY SYSTEM

Liquid-liquid equilibrium(LLE)data have been determined for the n-butyl alcohol-water-butyl acetateternary system and the related binary systems at 293.15,303.15 and 313.15 K.The experimentally determinedLLE data for the n-butyl alcohol-water binary system have been found to be in satisfactory agreementwith the available literature data.The correlation and prediction of the LLE data have been done byusing NRTL and UNIQUAC models.The model parameters of binary systems have been identified witha thermodynamic criterion.In the correlation of ternary LLE data,two objective functions(mole fractionand distribution constant)have been used for purpose of comparison.The effect of weighting in the firstobjective function has been examined.In predicting the ternary LLE with different sets of parameter valuesobtained for each of the constitutent binary systems,improved prediction results have been obtained bycomparing the results of different combinations of the sets of parameter values and choosing those givingthe best result.     

GAS–LIQUID REACTION KINETICS: A REVIEW OF DETERMINATION METHODS

The aim of this article is to provide comprehensive insight into the determination and interpretation of reaction kinetics of two-phase (gas–liquid) systems. Various aspects of the methodologies used for the measurements of kinetic parameters (such as equipment design, corresponding theoretical background, main steps, advantages, and limitations) are discussed in detail. In addition, an illustrating example is provided based on an industrially relevant absorption system.     

EXPERIMENTAL STUDIES AND PARAMETER OPTIMIZATION OF SEPARATION OF COPPER USING HOLLOW FIBER–SUPPORTED LIQUID MEMBRANE

The separation of copper from a leach liquor bearing 204.59 mol/m³ Cu, 40.83 mol/m³ Zn, 33.94 mol/m³ Co, 255.58 mol/m³ Ni, and 75.72 mol/m³ (NH₄)₂SO₄ has been carried out with a hollow fiber membrane using LIX 84-I as the mobile carrier. Central composite inscribed (CCI) design was used to design the experiments. The factors considered for the CCI design were pH, LIX 84-I concentration in the membrane phase, flow rate, and acid concentration in the strip solution. A reduced quadratic model was found to fit the experimental data. Detailed analysis of the effect of different factors as well as their interaction on the extraction of copper has been done. The optimized condition for maximum copper flux was found to be pH 4.5, 39.88% LIX 84-I, 360 mL/min flow rate, and 7% H₂SO₄ in strip solution. The highest copper flux of 7.46 × 10^?5 mol/m² · s was obtained experimentally at the above conditions, which is in good agreement with the predicted value of 7.57 × 10^?5 mol/m² · s.     

A review of: “MECHANICS AND THERMODYNAMICS OF DRYING”, By Markku Lampinen Helsinki University of Technology Espoo,Finland

ABSTRACT

The effects of conduction heating in a steam jacketed cylindrical dryer-cum stabilizer at the drying surface temperatures ranging from 100° to 120°C on thin layer conduction drying characteristics of raw and steamed rice bran were studied. Results show that both raw and steamed rice bran at 13.7·14.2 and 14.7 ·16 ·· 3 percent (d b) initial moisture contants (imc; respectively dried uncer fillinq-rate period only, where as steamed bran at 30·3 per cent imc dried initially under constant rate period for a very short time and then dried under fall ing-rate period. The drying surface temperature of 115°C can be taken as optimumu for conduction drying of both raw. and steamed rice bran. The empirical drying equations, developed for the above drying conditions. can be used to predict the drying time with fairly good accuracy.     

COBALT–NICKEL SEPARATION: THE EXTRACTION OF COBALT(II) AND NICKEL(II) WITH BIS(2-ETHYLHEXYL) PHOSPHINIC ACID (PIA-8) IN TOLUENE

The extraction behaviour of cobalt(II) and nickel(II) from sulfate solutions with bis(2-ethylhexyl) phosphinic acid (PIA-8) in toluene has been studied. Quantitative extraction of Co(II) was observed at pH 5.0–5.9 while that of Ni(II) at pH 6.8–7.0 with 0.03 M PIA-8 in toluene. The difference in pH_0.5 for Co(II) and Ni(II) was 1.9. The stoichiometry of the extracted species were determined by slope analysis method. The extraction reaction proceeds by cation exchange mechanism and the extracted species were Co · R₂(HR)₂ and Ni · R₂ · 2(HR)₂. Temperature dependance of the extraction equilibrium constants were determined to estimate the apparent thermodynamic functions (ΔG, ΔS and ΔH). The method was used for separation of cobalt(II) and nickel(II). Cobalt(II) was separated from nickel even at 1:20 (Co:Ni) ratio. The separation of cobalt(II) from nickel(II) was favoured with the increase in temperature.     

VISCOSITY STUDIES OF SYSTEM CaO–MgO–Al2O3–SiO2: 1, 40% SiO2*

The measurement of glass viscosities at elevated temperatures with an oscillating cylinder-type viscometer is described. Viscosity data are presented covering those compositions in the CaO–MgO–Al₂O₃–SiO₂ system which contain 40% SiO₂ and which are liquid at 1500°C. The pattern of the system of isokoms presented indicates that viscosity is closely related to the ratio of basic to acidic components. Theoretical aspects of the variation of viscosity with composition in silicate-aluminate systems are discussed in terms of silica-alumina polymers.     

PREPARATION AND ADSORPTION PROPERTIES OF THE POLYSTYRENE RESIN HAVING DIETHYLENETRIAMINE-N,N′- BIS(METHYLENEPHOSPHONATE) GROUP

Styrene-divinylbenzene copolymer beads containing diethylenetriamine-N,N′-bis(methylenephosphonate) group have been synthesized. The adsorption properties, of the present resin for some trivalent and bivalent metal ions have been examined. The selectivity sequence of the present resin at pH lower than 2.0 is as follows: Ga(III)> A1(III)> Sm(III)>Cu(II)>Co(II)>Zn(II)>Ca(II). The present resin reveals remarkable selectivity for the trivalent metal ions. The selective concentration of In(III) Ga(III) and Sm(III) from an acidic aqueous solution has been demonstrated by using a column of the present resin.     

SOLVENT EXTRACTION OF COBALT AND NICKEL IN BIS (2,4,4-TRI-METHYLPENTYL) PHOSPHINIC ACID, “CYANEX -272”

ABSTRACT A study has been made of the extraction of cobalt and nickel from sulfate solutions into bis(2,4,4 tri-methylpentyl) Phosphinic acid - “Cyanex 272”, diluent Esso solvent DX 3641, for both high and low metal loading in the organic phase. In dilute solution, 0.01 M, extraction constants and enthalpies were determined for both metals. The extraction of cobalt was always favored over that of nickel, increasing with increase in temperature. No structure change with temperature was found for the cobalt-Cyanex complex. Phase modifiers were found to effect the selectivity of “Cyanex 272” for cobalt.

At high metal loading, equilibrium curves for cobalt were fitted using semi-empirical curve fitting, while for nickel a straight line variation was observed. Organic phase polymerization was observed for both metals the degree of aggregation increasing with increase in loading. A step change increase in the viscosity of the organic phase was observed at high cobalt loading. Phase modifiers proved to be ineffective In reducing the increase in organic phase viscosity.     

REMOVAL OF BORON FROM BALÇOVA-IZMIR GEOTHERMAL WATER BY ION EXCHANGE PROCESS: BATCH AND COLUMN STUDIES

In this study, the efficiency of boron removal from Balçova geothermal water provided by the Izmir Geothermal Energy Company, Turkey, has been investigated using boron selective ion exchange resins Diaion CRB 02 and Dowex (XUS 43594.00) by batch and column methods. The results of the column studies have been evaluated in terms of type of resin and feed flow rate, and the effects of particle size and temperature have been investigated using the results obtained from batch kinetic studies. The data from the kinetic studies have been evaluated using pseudo-first-order and pseudo-second-order kinetics models. In addition, the classical diffusion models have been used to evaluate the kinetic data obtained to understand the rate-controlling mechanisms.     

LIQUID-LIQUID EQUILIBRIA OF ORGANIC COMPOUNDS: MEASUREMENT,CORRELATION AND PREDICTION†

The knowledge of phase equilibria is an important step in the development of extraction processes. This knowledge is usually gained from experiments. However, this procedure is expensive when a suitable solvent has to be found for a specific separation. Therefore methods for predicting phase equilibria are needed. While formerly these methods were largely based on empirical assumptions, the use of the concept of local compositions by Wilson⁶ offers a semi-empirical approach.

There is one disadvantage of this approach: the parameters of models like UNIQUAC or NRTL have to be fitted to different types of data, to liquid-liquid equilibria (LLE) for the immiscible pairs of components and to vapour-liquid equilibria (VLE) or other data for the miscible pairs in a system with mutual solubility.

To demonstrate the problem we performed measurements in the binary systems: n-octane/aniline and methylcylohexane/aniline. of both liquid-liquid equilibrium and vapour-liquid equilibrium: for the second type of measurements ebulliomeiry was used. The prediction of LLE has been improved with two new concepts. One is based on the well-known UNIFAC method. The use of the Lyngby-Dorlmund data bank made it possible to determine a new parameter table merely based on LLE data.

The second method is based on common UNIQUAC parameters which have been determined with the data base.     

STUDIES IN CHEMICAL PROCESS DESIGN AND SYNTHESIS: VI. A THERMOECONOMIC APPROACH TO THE EVOLUTIONARY SYNTHESIS OF HEAT EXCHANGER NETWORKS†

A thermoeconomic approach to the systematic evolutionary synthesis of energy-optimum and minimum-cost, heal exchanger networks is presented. The proposed approach can be applied by simple hand calculations and graphical manipulations to synthesis problems represented by either heat content diagrams or temperature interval diagrams. Applications of the approach have successfully generated optimum and suboptimum networks of five to ten process streams with much less time and effort compared to previous studies. It is shown that final networks for example synthesis problems can be obtained without performing cost evaluations of intermediate networks during the evolutionary synthesis.     

V-L EQUILIBRIUM OF WEAK ELECTROLYTE SOLUTION OF THE NH_3-CO2-H_2O,NH_3-H_2S-H_2O AND NH_3-SO_2-H_2O SYSTEM

In this paper we have systematically studied V-L equilibrium in ternary aqueous solutions containingvolatile electrolytes by introducing a ternary interaction term into Edwards generalized molecular thermody-namic model and optimizing several adjustable parameters.The program PARA9 with flexible functions ofdoing a series of calculations has been developed and carried out on a TQ-16 computer.It can be usedeither for directly calculating the V-L equilibrium or for optimizing the adjustable parameters.For the sys-toms(NH_3-CO_3-H_2O_3,NH_3-H_2S-H_2O and NH_3-SO_2-H_2O)satisfactory results have been obtained withrelative mean deviation of 5-10%.Besides,several sets of adjustable parameters and valuable information ofactivity coefficients,equilibrium concentrations of ions and molecules in solutions are obtained.     

USE OF BROMATE IN VOLUMETRIC ANALYSIS: IX,DETERMINATION OF ARSENIC AND ANTIMONY BY THE GYÖRY METHOD*

The determination of arsenic and of antimony by the oxidation of the hydrochloric acid solutions of their tervalent forms using standard bromate as oxidant by the Györy method has long been a preferred procedure. This method involves the use of strongly acid, hot solutions and nonreversible internal dye-stuff indicators. Difficulties result from the instability of the indicators under the required conditions. The published improvements as applied to the Györy method are discussed and evaluated. The new study of the old procedure shows that the use of a hot solution is not required. The experimental proof of this conclusion is given, and the use of the “electron beam sectrometer” and a modified “dead stop” equivalence-point determination has been applied to establish the concordance between the potentiometric and visual indicator applications. The performance of the various applicable internal indicators has been described and those preferred are specified.     

ION-EXCHANGE RESIN–CATALYZED SYNTHESIS OF POLYOXYMETHYLENE DIMETHYL ETHERS: A PRACTICAL AND ENVIRONMENTALLY FRIENDLY WAY TO DIESEL ADDITIVE

Polyoxymethylene dimethyl ethers (PODE_n) were synthesized via the reaction between dimethoxymethane (DMM) and trioxymethylene catalyzed by CT175, a macroporous strongly acidic cation-exchange resin. The influences of reaction conditions such as catalyst types, reaction temperature, time, pressure, catalyst dosage, and mass ratio of DMM to trioxymethylene were also investigated. Under the optimized conditions of m(dimethoxymethane):m(trioxymethylene) = 2.5:1, CT175 (7.5 wt.%), 90°C, 0.5 h, and 1.5 MPa, the conversion of trioxymethylene and the selectivity to PODE_3-8 was obtained as high as 89.0% and 64.2%, respectively. Moreover, the resin catalyst can be reused up to 20 times without obvious change in its activity. The 100% atom efficiency, green reaction process, mild reaction conditions, as well as easy workup make the protocol advantageous and acceptable.