Integrated Material and Process Evaluation of Metal-Organic Frameworks Database for Energy-efficient SF6/N2 Separation

<p>In this work, we proposed multi-scale screening, which employs both molecular and process-level models, to identify high-performing MOFs for energy-efficient separation of SF$_6$ and N$_2$ mixture. Grand canonical Monte Carlo (GCMC) simulations were combined with ideal adsorption process simulation to computationally screen 14,000 metal-organic frameworks (MOFs) for adsorptive separation of SF$_6$ \/ N$_2$. More than 150 high-performing MOFs were identified based on the GCMC simulations at the pressure and vacuum swing conditions, and subsequently evaluated using the ideal adsorption process simulation. High-performing MOFs selected for the VSA conditions are able to achieve the 90 \% target purity level of SF$_6$, but none of the selected MOFs for PSA conditions could. Cascade PSA configuration was proposed and adopted to improve the purity level of the separated SF$_6$. Cascade PSA configuration was also adopted to improve the purity. In the pump efficiency scenarios of 80, 20, and 10 \%, the VSA and cascade PSA cases were compared. Top-performing MOFs identified from the multi-scale computational approach were found to be able to produce 90\% purity SF$_6$ with 0.10 - 0.4 and 0.5 - 1.4 MJ per kg of SF$_6$ for VSA and PSA, respectively. We used experimental isotherm data available in the literature to evaluate the process-level performance of top-performing materials (HKUST-1, UiO-67) along with other materials (MIL-100(Fe), UiO-66, and zeolite-13X) with experimental isotherm data. We found that there is a reasonable agreement between using simulated and experimental isotherm data.<br></p>

Kinetic and isotherm studies for nickel ions’ biosorption by jute fabrics

Raw jute fabric was chemically modified with 1 % NaOH for 30 min, 17.5 % NaOH for 5 min ?r with 0.7 % NaClO2 for 30 and 60 min to study the influence of changes in fabrics? chemical composition and carboxyl group quantity on fabrics? biosorption capacity for nickel ions. The effects of contact time and initial nickel ions? concentration on the fabrics? biosorption capacity were also investigated. The obtained results reveal that the biosorption of nickel ions can be explained by the pseudo-second-order kinetic model, while the experimental isotherm data fit better with the Langmuir model. The calculated ratios between the jute fabrics? maximal biosorption capacity (6.30-12.06 mg g-1) and carboxyl group quantity pointed out that approximately half of the fabrics? carboxyl groups would be involved in binding nickel ions during biosorption. Therefore, the carboxyl group quantity can be used to predict the jute fabrics? maximal biosorption capacity toward nickel ions. In the case of oxidized jute fabrics, the lignin removal, and consequently increased content of cellulose and hemicelluloses, also contributed to higher biosorption capacity.

Experimental investigation of activated carbon prepared from apricot stones material (ASM) adsorbent for removal of malachite green (MG) from aqueous solution

The adsorption of malachite green onto activated carbon prepared from apricot stones material has been investigated at batch conditions. The effects of contact time (0–60 min), initial pH (3–11), agitation speed (100–700 r/min), temperature (298–343 K), adsorbent dose (1–10 g/L), and malachite green concentration (4.45–17.6 mg/L) on the malachite green adsorption by apricot stones material have been studied. Malachite green removal increases over the contact time until equilibrium. The batch adsorption experiments were carried out to optimize the physical parameters on the malachite green removal efficiency. It has been found that 23.80 mg/g at 25°C and 88.05 mg/g at 70°C were removed. The kinetic parameters, rate constants and equilibrium adsorption capacities, were calculated and discussed for each kinetic model. The adsorption of malachite green onto apricot stones material is well described by the pseudo second-order equation. The experimental isotherm data were analyzed by different models; the adsorption follows the Langmuir model, providing a better fit of the equilibrium data. The thermodynamics parameters such as the negative free energy Δ G° (−0.191 to −4.447 kJ/mol) and positive enthalpy Δ H° (50.86 kJ/mol) indicated the spontaneous and endothermic nature of the malachite green adsorption with a chemisorption process.

Removal of methylene blue from aqueous solution using cocoa (Theobroma cacao) nib-based activated carbon treated with hydrochloric acid

Chemical activation process was applied to prepare a cocoa nib-based activated carbon using potassium carbonate (K2CO3). The performance of the activated carbon in removing Methylene Blue from aqueous solution was investigated by batch adsorption studies. The adsorptive properties were studied in terms of initial concentration (C0: 100-300 mg/L) and contact time effects. The experimental isotherm data fitted well the Langmuir and Temkin models. The adsorption kinetic followed the pseudo-second-order model and Boyd model explained the mechanism of adsorption. The results indicate that the chemically produced activated cocoa nib carbon has significant potential to be used as an adsorbent material for adsorption of Methylene Blue from aqueous solution.

Effectiveness of beetroot seeds and H3PO4 activated beetroot seeds for the removal of dyes from aqueous solutions

Raw beetroot seeds (BS) and H3PO4 activated beetroot seeds (H3PO4-BS) were evaluate for their effectiveness in removing methylene blue (MB) and malachite green (MG) from aqueous solution. BS were carbonized at 500°C for 2 h, and then impregnated with phosphoric acid (phosphoric acid to BS ratio of 1.5 g/g). The impregnated BS were activated in a tubular vertical furnace at 450°C for 2 h. Batch sorption experiments were carried out under various parameters, such as solution pH, adsorbent dosage, contact time, initial dyes concentration and temperature. The experimental results show that the dye sorption was influenced by solution pH and it was greater in the basic range. The sorption yield increases with an increase in the adsorbent dosage. The equilibrium uptake was increased with an increase in the initial dye concentration in solution. Adsorption kinetic data conformed more to the pseudo-second-order kinetic model. The experimental isotherm data were evaluated by Langmuir, Freundlich, Toth and Dubinin–Radushkevich isotherm models. The Langmuir maximum monolayer adsorption capacities were 61.11 and 74.37 mg/g for MB, 51.31 and 213.01 mg/g for MG, respectively in the case of BS and H3PO4-BS. The thermodynamic parameters are also evaluated and discussed.

On the Optimal Use of Isotherm Models for the Characterization of Biosorption of Lead Onto Algae

In this study the experimental isotherm data of biosorption of Pb(II) onto algae was modeled using several models. These models are: Langmuir, Hill-Sips, Brouers-Sotolongo, Brouers-Gaspard, and Redlich-Peterson models. The coefficients of each model were determined by non-linear fitting using Mathematica9 program. The maximum Pb(II) removal rate increased with the increase of temperature and reached the maximum value (98%) at the temperature of 40°C. Even if the R2 error quantity is not the unique and always the best measure for nonlinear fitting, the Brouers-Sotolongo model gives in all cases the best fit and is definitely the most suitable one to satisfactorily describe bioisorption of Pb(II) on the algal biomass. In addition, this study shows that a complete set of data is necessary to have a good representation of the isotherm.

A New Model for Predicting Sorption Isotherm of Water in Foods

A new model for predicting sorption isotherms of type II and III based on the Polanyi theory is proposed. This model allows the prediction of the sorption isotherms at different temperatures from one experimental isotherm. The theoretical predictions of isotherms and isosteric heat were validated successfully using data from literature for twenty one foods. This method allows total experimental time and operation costs to be reduced.