ABSTRACT Tetrahydrofuran (THF) manufacture is explored in this work using the route from 1, 4 butanediol (BD) in the fixed bed chromatographic reactor (FBCR). Major problem faced in this manufacture is the existence of THF-water minimum boiling azeotrope. Use of FBCR helps to circumvent the azeotrope, thereby offering a simplified process. Binary adsorption experiments, reaction in the FBCR environment and regeneration experiments are presented. Use of molecular sieves and rectification helps to obtain almost pure THF as the product and BD for recycle. A complete process to manufacture THF from BD is thus developed.

ABSTRACT In the separation of CO2 from flue gas by membrane technology, the development of high permeability and selectivity, environmentally friendly and inherent merit materials play a vital role in efficient membrane processes. For this purpose, chemically active polydopamine (PDA) was successfully synthesized by solution-oxidation method and used in the functionalization and modification of graphene oxide (GO) and GO-polyethylene glycol (PEG) nanomaterial as bio-fillers were incorporated into polyethersulfone (PES) membrane as the basis of the fabricated mixed membrane matrix (MMM). The chemical, physical, thermal behavior and crystallographic structure of bio-fillers and membranes were studied by several analyses. The related functional groups are successfully obtained during the three steps of synthesis, including PEG-GO, PDA-PEG-GO and PDA-GO synthesis. The separation performance of the synthesized-MMM for 30% CO2/70% N2 gas mixture was studied, which resulted to the selectivity of 577.8 and permeability of 416.05 Barrer for PES-PDA-PEG-GO membrane under humidified condition. As a case study, the separation performance of MMM was evaluated for CO2 separation from a typical flue gas that resulted in a selectivity of 339.56 and permeability of 237.5 Barrer. According to the results obtained from a typical flue, the synthesized membrane has an acceptable potential for CO2 separation and industrial uses.

ABSTRACT Dyes are significant contributors to the chemical oxygen demand of the wastewater produced by textile industries. In the current study, naturally occurring, inexpensive, non-hazardous clay was pillared and used to remove Acid Green 25 dye (AG) from aqueous solutions. The pseudo-second-order model provided a better fit to describe the adsorption kinetics data for AG, with a rate constant of 9.82 × 10−3 g/mg min. Langmuir isotherm provided a better fit for describing the adsorption isotherm of the AG dye. Thermodynamic analysis revealed that adsorption was exothermic with an enthalpy change of −48 kJ/mol. The effects of pH, adsorbent dosage, and initial concentration of AG dye on adsorption capacity were analyzed, and an empirical model was developed using the response surface methodology approach. Optimization studies revealed that a maximum adsorption capacity of 105.15 mg/g for the AG dye could be achieved at a pH of 2, an adsorbent dosage of 1.5 g/L and an initial dye concentration at its upper limit of 200 mg/L. The adsorbent could be regenerated and reused up to three adsorption cycles, and the desorbed dye and treated water may be reused in the dyeing process, thereby making the entire operation circular. Circularity reduces the cost of production and makes the process more sustainable. Mechanistic insights revealed that electrostatic interaction was the driving force for the adsorption of AG dye. In this work, it has been demonstrated that after pillaring, clay-based material may be used as an effective adsorbent for treating dye-containing wastewater.

ABSTRACT Living organisms are at great risk from the highly toxic metal cadmium (II). It is not allowed to be in industrial effluent or drinking water that is dumped into cadmium-containing water bodies. It has been classified as a carcinogen by the IARC and the US EPA. Thus, it is essential to discover a practical and economical technique for removing cadmium from an aqueous solution. In the present work, a novel and easy-to-prepare component of graphene oxide/orange peel/chitosan composite (GO-OP-CS) was prepared and examined using various analytical techniques as a hybrid product with improved physicochemical properties and metal ion Cd(II) adsorption capabilities. The results showed that Cd (II) ion adsorption occurred initially fairly fast and that a pH of 6 was optimal for both adsorption and removal of Cd (II) ions. The thermodynamic analysis revealed that the adsorption of Cd(II) is spontaneous and exothermic. The experimental results showed that the functional groups present on the adsorbent surfaces (such as hydroxyl, carboxyl, epoxy, amine, and so on) led to the improvement of the Cd(II) metal’s ability to absorb. This novel composite exhibited a high adsorption capacity (qmax) of 537.63 mg/g. The results of the toxic Cd(II) sorption using the synthesized composite showed that its adsorption kinetics and sorption isotherm confirmed the pseudo-second-order and Langmuir models, respectively. The proposed method is also reliable for Cd(II) sorption for preconcentration and remediation before Cd testing from genuine samples, such as wastewater, digested tobacco, and e-battery samples.

ABSTRACT Efficient and eco-friendly technologies are required to reduce the environmental effects of the beneficiation plants. Recently, there has been an interest in environmentally friendly alternative depressants. This study explored the effects of various depressants (AERO633, AERO7260, DP3124, DP3125, carboxymethyl cellulose (CMC), Cyquest4000, and sodium silicate) on chalcopyrite flotation. The experimental results indicated that AERO7260 has the best effect on chalcopyrite flotation, and the dosage is 50 g/t, it can improve the chalcopyrite recovery up to 93.35% as well as chalcopyrite grade up to 36.97%. Meanwhile, AERO7260 had an obvious depression effect on pyrite, reducing pyrite grade to 61.10% and pyrite recovery to 3.35%. Given its low reagent dosage and high selectivity, AERO7260 is a promising depressant that can be used for chalcopyrite flotation. The use of organic depressants will significantly aid the transition to ecologically friendly and sustainable processes. This study shows that organic depressants in chalcopyrite flotation can replace the existing inorganic depressants used in the depression of gangue minerals and that metals can be recovered at high performance by processing appropriately.

ABSTRACT The study aimed to create a chitosan/graphite composite (CGC) using the impregnation method to optimize its adsorptive efficiency for methylene blue dye from synthetic waste water. The composite adsorbent material was synthesized using a chitosan to expanded graphite ratio of 5% and acetic acid and glutaraldehyde. Expanded graphite was prepared by reacting it with H2SO4 and H2O2 for 90 minutes at room temperature. The specific surface area of graphite increased from 1193.75 m2/g to 1223.648 m2/g. The composite adsorbent material was synthesized using the impregnation method, with chitosan to expanded graphite ratio of 75:25. The CGC was characterized using FTIR, XRD, BET, SEM, and point of zero charge analysis. The adsorption of methylene blue dye onto CGC was optimized by response surface statistical experimental design method to achieve a removal efficiency of 98.61% at 5.24 initial concentration, pH of 9.98, and 95.43-minute contact time. The Langmuir isotherm best fitted the adsorption process, with an R2 value of 0.9974 and adsorption capacity of 98 mg/g. The kinetics of adsorption were best fitted to pseudo-second order with K value 0.0378. The composite was found to be the best alternative adsorbent for removing methylene blue dye from textile wastewater.

ABSTRACT Ultrasound-assisted extraction (UAE) of galactomannan from the endosperm of ripe carob seeds (LBG.S3) was investigated through response surface methodology (RSM). The optimized UAE conditions were an extraction time of 40 minutes, a temperature of 45°C, and a solid-liquid ratio of 1:50 g/mL. Under these settings, the experimental yield of galactomannan was 47.53 ± 2.55%, which is closely aligning with the expected value of 49.78 ± 3.15%. The yield of galactomannan extracted from unripe carob seeds (LBG.S2) under the same optimal conditions was significantly higher 56.73 ± 2.76% (p < 0.05) than the yield of LBG.S3. The infrared spectroscopy (FT-IR) characterization revealed the existence of various functional groups in the spectrum of galactomannan extracted from unripe seeds, not found in LBG.S3. The galactomannan from ripe carob seeds exhibited superior functional properties, including solubility, emulsion and stability capacity, water and oil holding capacity, and viscosity, compared to LBG.S2. In vitro, tests demonstrated notable anti-inflammatory activity for both LBG.S2 and LBG.S3, as observed through the inhibition of bovine serum albumin (BSA) protein denaturation by heat and the membrane stabilization test. Carob galactomannan is a potential source of bioactive polysaccharides with anti-inflammatory and functional properties that can be used in the food and pharmaceutical industries.

ABSTRACT Nano-sized composite ion-exchanger can be applied as an electrochemically switchable ion-exchanger for waste water treatment, especially in the separation of heavy metal ions from the polluted aquatic system. Advanced polyaniline/Ti(IV) iodomolybdate nanocomposite ion-exchanger have been synthesized by in-situ chemical oxidation polymerization shows better ion-exchange capacity than individual inorganic counterpart. The physico-chemical characterization was done by FT-IR, XRD, simultaneous TGA-DTA, SEM, HR-TEM and electrochemical impedance studies. According to impedance/dielectrical study, it has high resistivity in the low-frequency region. The distribution studies and binary separation revealed that the ion-exchange material is highly selective for Pb2+, which is a most important environmental pollutant. Thus, PANI/TIM nanocomposite ion-exchanger can be used for Pb(II) ion-selective membrane for the treatment of aquatic pollutants in future.

ABSTRACT The aim of this study was to develop a layered ammonium tin phosphate as a potential sorbent for removal of Pb2+ ions by exchange/sorption or other mechanism from contaminated solutions. A layered ammonium tin phosphate (NH4-SnP), δ-SnP – NH4 was synthesized using the hydrothermal process. XRD pattern of the NH4-SnP revealed that the final product obtained was δ-tin (IV) phosphate with the d(001)-spacing of about 14.8 Å containing ammonium ions and water molecules in the interlayers. In order to investigate the removal efficiency of Pb2+ cations by the NH4-SnP, batch-type of sorption experiments were carried out with 2 days of equilibration time at room temperature. Also, the kinetics of reaction was performed at room temperature to determine equilibrium time. The sorption isotherms for Pb2+ cations indicated that NH4-SnP showed high affinity for these ions with all the concentrations used. In addition, kinetic data showed preference for Pb2+ cations between NH4 + cation on the exchanger and Pb2+metal cation in solution. Based on these results, NH4-SnP can be proposed as an excellent sorbent for not only removal but also immobilization of Pb2+ ions from water and wastewater. Pb2+ ions were found to be immobilized as insoluble pyromorphite, Pb5(PO4)Cl after high uptakes.

ABSTRACT Nepheline syenite is primarily an alumino-silicate rock which contains a major amount of potassium and aluminum. After potassium recovery through chloridizing roasting followed by water leaching method, the roast leach residue of nepheline syenite was considered for the aluminum extraction process due to its ample aluminum content. Sulfuric acid is chosen over other acids as it prevents the leaching of calcium. A 2^3 full factorial design was employed to study the effects of acid concentration, time, and temperature. Furthermore, to enhance the recovery and to forbid the leaching of silicon, autoclave leaching was preferred. Iron is generally leached with aluminum in the acid leaching process which could be removed effectively by pH adjustment. The leached liquor obtained after purification is evaporated by using a hot water bath. The liquor concentrated on slow evaporation to a point where aluminum sulfate started precipitating. Then, the concentrated liquor was kept overnight at 8°C in a cooling incubator. Aluminum sulfate was produced with 99.80% purity.