Optimal Operation of Simulated Moving Bed Technology on Utilization of Naphtha Resource

Simulated moving bed (SMB) technology has attracted more and more attention in recent decades. The simulated moving bed (SMB) technology on optimal utilization of naphtha resource was studied in this paper. A simulated moving bed equipped with 16 columns was used to separate normal paraffins from naphtha. The effects of temperature (T), switching time (t_s), extract oil flow rate (L_AD), feed flow rate (L_F), and desorbent flow rate (L_D) on the separation performance were investigated, and the desorbent recycle process was simulated by Aspen Plus. The results showed that the optimal conditions for simulated moving bed were operation temperature (T) of 170°C, switching time (t_s) of 900 s, extract oil flow rate (L_AD) of 10 mL/min, feed flow rate (L_F) of 5 mL/min, and desorbent flow rate (L_D) of 20 mL/min. Through the SMB and the desorbent recycle system, the purity of the de-solvent extract oil (DEO) reached 98% and the purity of the de-solvent raffinate oil (DRO) reached 92%, which were the high-quality feed for the ethylene cracking process and the catalytic reforming process, respectively.     

Performance of Low Cost Ceramic Microfiltration Membranes for the Treatment of Oil-in-water Emulsions

Using the uniaxial compaction method, ceramic disk type microfiltration membranes were fabricated using mixtures of clays to yield membranes M₁, M₂, and M₃. These were obtained with distinct compositions of raw materials at a sintering temperature of 900°C. Membrane characterization was conducted using thermogravimetric analysis (TGA), particle size distribution (PSD), X-ray diffraction (XRD), and scanning electron microscope analysis (SEM). Morphological characterization of these membranes includes the evaluation of average porosity, pore size, mechanical stability, chemical stability, and hydraulic permeance. With varying composition of the raw materials, it is observed that the average porosity and pore size of the membrane varied between 23–30% and 0.45 to 1.30 µm. For all membranes, the flexural strength varied within the range of 10-34 MPa. Chemical stability tests indicate that the membranes are stable in both acidic and basic media. The hydraulic permeance of M₁, M₂, and M₃ membranes is about 3.97 × 10^?6, 2.34 × 10^?6, and 0.37 × 10^?6 m³/m² s kPa, respectively. Further, the performance of these membranes was studied for the microfiltration of synthetic oily wastewater emulsions. Amongst all membranes, membrane, M₂ performance is satisfactory as it provides oil rejection of 96%, with high permeate flux of 0.65 × 10^?4 m³/m² s at a lower transmembrane pressure differential of 69 kPa for the oil concentration of 200 mg/L.     

Fractionation of Lignocellulosic Materials for the Biorefinery: Separation and Characterization of Lignin from Calamagrostis angustifolia Kom

Dewaxed Calamagrostis angustifolia Kom was pretreated with hot water at 60 and 90°C for 3 h, and then the residue obtained was successively treated with 70% ethanol, and 70% ethanol containing 0.2%, 1.0%, 2.0%, 4.0%, and 8.0% NaOH at 80°C for 3 h. The dissolved components were subjected to further separation to get eight lignin fractions, which were characterized by gel permeation chromatography, Fourier transform infrared, and sugar analysis. All the lignin fractions had small weight-average molecular weights between 810 and 2580 g/mol. Two typical lignins, L₃ (prepared with 70% ethanol) and L₅ (prepared with 70% ethanol containing 1.0% NaOH), were further analyzed using ¹H, ¹³C NMR and HSQC spectroscopy. Signals from guaiacyl (G), syringyl (S), and p-hydroxyphenyl (H) units observed in aromatic/olefinic region of HSQC spectra indicated that the lignin from Calamagrostis angustifolia Kom could be classified as “GSH” lignin. In aliphatic-oxygenated region, β-O-4′ together with small amounts of β-5′, β-β′, and p-hydroxycinnamyl alcohol end group were the main interunit linkages observed. Aqueous ethanol, which could avoid the cleavage of ether bonds in lignin at neutral condition, was more effective than water on lignin extraction.     

Co-Adsorption/Filtration of Heavy Metal Ions from Water using Regenerated Cellulose UF Membranes Modified with DETA Ligand

The current study investigates the coupled filtration/adsorption performance of regenerated cellulose (RC) ultrafiltration membranes functionalized with diethylenetriamine (DETA) as a metal-chelating ligand. Lead and copper ions with various concentrations (10–50 ppm) were selected as model adsorbing metals. To investigate the dynamic adsorption performance of the ions, different parameters including initial metal concentration, time of oxidization reaction, ligand concentration, and solution pH were studied. The maximum removal of Pb(II) and Cu(II) proposed by the modified membranes from their single salt solutions were 87% and 83%. Besides, the removal percentages of 56 and 50 were obtained for the competitive adsorption of Pb(II) and Cu(II) ions from their mixed solution, respectively. The selectivity factor was calculated as 1.25 indicating the potential of the process for selective adsorption of the ions. Langmuir and Freundlich isotherms were employed to describe the adsorption equilibria with the first model providing the best fit. Reusability tests showed that the modified membranes can be effectively regenerated by 0.1 M HCl eluting solution and successively reused in dynamic adsorption process.     

Separation of Simulated Mixed Mo(VI) and V(V) From HNO3 and HCl Solutions by Selective Extraction and Stripping with Tri-N-Butyl Phosphate as Extractant

Equilibrium study was carried out to determine the optimum conditions required for Mo(VI) extraction from HNO₃ solutions and subsequently, simulated mixed Mo(VI), and V(V) were extracted from HNO₃ (pH = 1.0) and 6.0 mol L^?1 HCl solutions with TBP dissolved in n-hexane. The variation of pH (selective extraction) and selective stripping were investigated as methods of separation of Mo(VI) and V(V). The latter method was found inefficient for separations from HNO₃ solutions (pH = 1.0) except supplemented with selective stripping (back-extraction with 2.0 mol L^?1 H₂SO₄/14.5 mol L^?1 NH₄OH). While from 6.0 mol L^?1 HCl, selective stripping was adequate to quantitatively strip in turns the Mo(VI) and V(V) co-extracted into the TBP phase. About 100% of the co-extracted V(V) from the HCl medium was stripped in a two-stage process, in contrast to a single-stage required for Mo(VI) of the same result. The selective stripping method was found to be better because an initial appreciable co-extraction had occurred prior to stripping separation. Based on analytical and spectra data, the extracted complexes from HNO₃ and HCl media were formulated as ((MoO₂)_7–8n(VO₂)_2n · (NO₃)₁₆) ^(16–18)n- · m TBP (where n>m) and (MoO₂Cl₂ · VO₂ Cl) · xTBP, respectively.     

Study on Potassium Permanganate Chemical Treatment of Discarded Reverse Osmosis Membranes Aiming their Reuse

Membrane-based industrial desalination/demineralization plants generate a considerable amount of discarded membranes. This work studies the effects of the chemical treatment with potassium permanganate solutions in combination with chemical cleaning of three years old composite polyamide/polysulfone reverse osmosis membranes (8″ modules) in order to make them reusable in other applications than reverse osmosis and to increase their life cycles. The performance of membranes with 60 cm² was evaluated in terms of water permeate flux and salt rejection, two properties that can be easily measured in industrial systems. Potassium permanganate treatment degraded the selective layer, improving the water permeate flux of at least 15% from its initial value at the expense of decreased salt rejection. The formation of a manganese oxide layer was detected which reduced subsequent oxidative treatment efficacy. Citric acid was used as a cleaning agent after the oxidation steps, removing part of the manganese oxide layer; the result was an enhanced oxidative process, which increased the permeate flux even more and decreased the loss of salt rejection. Furthermore, to verify the stability of the treatment, the membrane was submitted to a long-term oxidizing experiment.     

Integrated Membrane Bioreactor for Water Quality Control in Marine Recirculating Aquaculture Systems

The aquaculture live feed organisms Acartia tonsa (a calanoid copepod, experiment 1) and Brachionus “Cayman” (a rotifer, experiment 2) were cultivated in marine recirculating aquaculture systems (RAS), respectively. The pilot plant was built as a combination of conventional RAS (cRAS) and as a modified RAS which implemented an ultrafiltration membrane bioreactor (MBR) for the removal of fine suspended solids and colloidal particles as part of the treatment system (mRAS). The two treatment schemes were connected to the same biofilter (a moving bed bioreactor). In the first experiment, the membrane was operated with no extraction of concentrate, and hydraulic retention time (HRT) of 6 hours (i.e., water exchange in the cultivation tanks of 4 times per day). In the second experiment, the membrane was operated with daily extraction of concentrate, and HRT of 12 hours. Results show that the MBR option is more efficient in removing particles from the recycle stream than conventional RAS. However, the impact this has on the number of particles in the live feed cultivation tanks is not readily apparent based on particle analysis. The amount of suspended solids added during feeding exceeds the amount removed in the recycle system. This requires a higher recirculation rate and different membrane operating conditions.     

Comparative Evaluation of Tri-n-butyl Phosphate (TBP) and Tris(2-ethylhexyl) Phosphate (TEHP) for the Recovery of Uranium from Monazite Leach Solution

Separation of U(VI) from Th(IV) and rare earth elements (REEs) present in monazite leach solution (nitric acid medium) has been studied using tris(2-ethylhexyl) phosphate (TEHP) and tri-n-butyl phosphate (TBP) dissolved in n-paraffin as solvents under varying experimental conditions such as nitric acid, extractant and metal ion concentrations etc. There is an increase in distribution ratio of U(VI) (D _U ) with increase in aqueous phase acidity up to 5 M HNO₃ beyond which a decrease is observed. Typically for 1 × 10^?3 M U(VI), the D_U values increase from 8 (0.5 M HNO₃) to 80 (5 M HNO₃) for 1.1 M TEHP, and from 2 (0.5 M HNO₃) to 43 (5 M HNO₃) for 1.1 M TBP in n-paraffin. The separation factors of U(VI) (β: D_U/D_M) over metal ions (M) such as Th(IV) and Y(III) (chosen as a representative of heavy REEs) are better for TEHP than TBP at all nitric acid concentrations. Batch solvent extraction data have been used to construct the McCabe-Thiele diagrams for the recovery of U(VI) employing TEHP as the extractant. A process flow sheet has been proposed with 0.2 M TEHP in n-paraffin as solvent for the recovery of U(VI) from simulated monazite leach solution in HNO₃ medium.     

Simulations of Membrane Gas Separation: Chemical Solvent Absorption Hybrid Plants for Pre- and Post-Combustion Carbon Capture

Solvent absorption and membrane gas separation are two carbon capture technologies that show great potential for reducing emissions from stationary sources such as power plants. Here, plants combining chemical solvent absorption and membrane gas separation are considered for post-combustion capture as well as pre-combustion capture. In all ASPEN HYSYS simulations the membrane stage initially concentrates CO₂ into either the permeate or the retentate stream, which is then passed to a monoethanolamine (MEA) based solvent absorption process. In particular, post-combustion capture scenarios examined a membrane that is selective for CO₂ against N₂, while for the pre-combustion scenario a H₂-selective membrane was studied. It was found the energy demand of the combined hybrid plant was always more than that of a stand alone MEA solvent process. This was mainly due to the need to generate a pressure driving force upstream of the membrane in the post-combustion scenario or to recompress downstream gas streams in the pre-combustion scenarios. For both scenarios concentrating the CO₂ in the feed to the solvent system reduced the absorber column height and diameter, which could represent a CAPEX saving for the hybrid plant, dependent upon the membrane price. The use of a hydrogen selective membrane downstream of an oxygen fired gasifier was identified as the most prospective scenario, as it led to significant reductions in absorber size, for a relatively small membrane area and energy penalty.     

Polymer Ion-Exchangers Modified with Zirconium Hydrophosphate for Removal of Cd2+ Ions from Diluted Solutions

Hybrid ion-exchangers have been synthesized by modification of strongly acidic cation-exchange resin with zirconium hydrophosphate. The samples were investigated with scanning and transmission electron microscopy and standard contact porosimetry. Single nanoparticles and their aggregates have been found in the polymer. The nanoparticles in transport pores increase the electrical conductivity of ion-exchanger from 0.21 to 0.65 Ohm^?1 m^?1. The diffusion coefficient of Cd²⁺ ions reaches 2.43 × 10^?11 m² s^?1 for initial resin and (2.50–4.34) × 10^?11 m² s^?1 for nanocomposites. The inorganic constituent improves Cd²⁺ recovery from a solution, which contains also Ca²⁺ and Mg²⁺. The degree of Cd²⁺ removal is 18% for non-modified resin and 99% for the sample containing 38 mass% zirconium phosphate.