Single Aqueous Solutions Research Articles

Kinetic effect of single MgCl2 and NaCl aqueous solutions on ethane hydrate formation

Experimental data on the kinetics of C2H6 hydrate formation in the presence of pure water and two aqueous single solutions, MgCl2 and NaCl, are presented in this study. The measurements of experimental hydrate formation process were performed in a high pressure reactor at 276.15 K, at initial pressure range of 2.0–2.4 MPa, and solution concentration range of 2.34–10 wt%. The effect of solution concentration and initial pressure on the induction time, gas consumption, conversion, and storage capacity and growth rate was examined. It was observed that with the increase of the solution concentration, the induction time increased, while the storage capacity and the number of moles of C2H6 consumed decreased. A diffusion-reaction kinetics model was employed to predict the hydrate growth rate at the beginning of hydrate formation. The results showed that the addition of MgCl2 and NaCl decreased the apparent rate constant, and MgCl2 had a greater effect than NaCl in inhibiting the hydrate growth.

Adsorption studies of methylene blue and gentian violet on sugarcane bagasse modified with EDTA dianhydride (EDTAD) in aqueous solutions: Kinetic and equilibrium aspects

In this study the adsorption of cationic dyes by modified sugarcane bagasse with EDTA dianhydride (EB) was examined using methylene blue (MB) and gentian violet (GV) as model compounds in aqueous single solutions. The synthesized adsorbent (EB) was characterized by FTIR, elemental analysis, and BET. The capacity of EB to adsorb dyes was evaluated at different contact times, pH values, and initial dye concentrations. According to the obtained results, the adsorption processes could be described by a pseudo-second-order kinetic model. The adsorption isotherms were well fitted by the Langmuir model. Maximum adsorption capacities for MB and GV on EB were found to be 202.43 and 327.83 mg/g, respectively. The free energy change during adsorption of MB and GV was found to be −22.50 and −24.21 kJ/mol, respectively, suggesting that chemisorption is the main mechanism controlling the adsorption process.

Removal of Co(II), Cu(II) and Pb(II) ions by polymer based 2-hydroxyethyl methacrylate: thermodynamics and desorption studies

Removal thermodynamics and desorption studies of some heavy metal ions such as Co(II), Cu(II) and Pb(II) by polymeric surfaces such as poly 2-hydroxyethyl methacrylate (PHEMA) and copolymer 2-hydroxyethyl methacrylate with monomer methyl methacrylate P(MMA-HEMA) as adsorbent surfaces from aqueous single solution were investigated with respect to the changes in pH of solution, adsorbent composition, contact time and temperature in the individual aqueous solution. The linear correlation coefficients of Langmuir and Freundlich isotherms were obtained and the results revealed that the Langmuir isotherm fitted the experiment results better than Freundlich isotherm. Using the Langmuir model equation, the monolayer removal capacity of PHEMA surface was found to be 0.7388, 0.8396 and 3.0367 mg/g for Co(II), Cu(ΙΙ) and Pb(II) ions and removal capacity of P(MMA-HEMA) was found to be 28.8442, 31.1526 and 31.4465 mg/g for Co(II), Cu(ΙΙ) and Pb(II) ions, respectively. Changes in the standard Gibbs free energy (ΔG0), standard enthalpy (ΔH0) and standard entropy (ΔS0) showed that the removals of mentioned ions onto PHEMA and P(MMA-HEMA) are spontaneous and exothermic at 293–323 K. The maximum desorption efficiency was 75.26% for Pb(II) using 0.100 M HNO3, 70.10% for Cu(II) using 0.100 M HCl, 59.20% for 0.100 M HCl 63.67% Co(II).

Removal of Ca(II) and Mg(II) from aqueous single metal solutions by mercerized cellulose and mercerized sugarcane bagasse grafted with EDTA dianhydride (EDTAD)

In a previous work, chemically modified cellulose (EMC) and sugarcane bagasse (EMMB) were prepared from mercerized cellulose (MC) and twice-mercerized sugarcane bagasse (MMB) using ethylenediaminetetraacetic dianhydride (EDTAD) as modifying agent. In this work we described in detail the modification of these materials in function of reaction time and EDTAD amount in the reaction media. The resistance of ester bond at pH 1, 2, 11, and 12 was also evaluated by FTIR. The results were used to model the hydrolysis process and a kinetic model was proposed. The modified materials (EMMB and EMC) were used to adsorb Ca 2+ and Mg 2+ ions from aqueous single solutions. The adsorption isotherms were developed at two pH values. These materials showed maximum adsorption capacities for Ca 2+ and Mg 2+ ions ranging from 15.6 to 54.1 mg/g and 13.5 to 42.6 mg/g, respectively. The modified material from sugarcane bagasse (EMMB) showed larger maximum adsorption capacities than modified material from cellulose (EMC) for both metals.

The study of adsorption characteristics Cu 2+ and Pb 2+ ions onto PHEMA and P(MMA-HEMA) surfaces from aqueous single solution

The adsorption characteristics of Cu 2+ and Pb 2+ ions onto poly2-hydroxyethyl methacrylate (PHEMA) and copolymer 2-hydroxyethyl methacrylate with monomer methyl methacrylate P(MMA-HEMA) adsorbent surfaces from aqueous single solution were investigated with respect to the changes in the pH of solution, adsorbent composition (changes in the weight percentage of MMA copolymerized with HEMA monomer), contact time and the temperature in the individual aqueous solutions. The linear correlation coefficients of Langmuir and Freundlich isotherms were obtained. The results revealed that the Langmuir isotherm fitted the experimental results better than the Freundlich isotherm. Using the Langmuir model equation, the monolayer adsorption capacity of PHEMA surface was found to be 0.840 and 3.037 mg/g for Cu 2+ and Pb 2+ ions and adsorption capacity of (PMMA-HEMA) was found to be 31.153 and 31.447 mg/g for Cu 2+ and Pb 2+ ions, respectively. Changes in the standard Gibbs free energy (Δ G 0), standard enthalpy (Δ H 0) and standard entropy (Δ S 0) show that the adsorption of mentioned ions onto PHEMA and P(MMA-HEMA) are spontaneous and exothermic at 293–323 K.