Acid-activated Montmorillonite Research Articles

Green synthesis of 1,3-Thiazolidin-4-ones derivatives by using acid-activated montmorillonite as catalyst

An environmentally friendly, clean, and applicable methodology for synthesizing 1,3-Thiazolidin-4-one derivatives was developed. This method produced the target compounds in high yields and short reaction times by using solvent-free reaction conditions with heterogeneous catalysts, montmorillonite (MT) and acid-activated montmorillonite (acid-MT). MT and acid-MT were investigated in the synthesis using a variety of techniques, including conventional heat, ultrasonic, and microwave irradiation, with the investigation of two types of factors, namely time and temperature. X-ray diffraction, N2 adsorption–desorption, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy were used to characterize the MT and acid-MT catalysts. FTIR, 1H NMR, 13C NMR, and mass spectra were used to characterize each product. The ring-cyclization step, with its short time and high yield percentage, is the most important factor for the strength of the prepared catalyst, acid-MT. Additionally, the acid-MT catalyst was easily recoverable and can be reused up to five times without suffering a substantial reduction in catalytic activity.

Coagulation-centered three-step approach for removing by-product organic pollutants from tetrabromobisphenol A industrial wastewater: Experimental and theoretic investigations

The challenge of meeting discharge standards for tetrabromobisphenol A (TBBPA) production wastewater, characterized by high concentrations of organic by-products, necessitates effective treatment methods. This study identifies 2,4-dibromophenol, 2,6-dibromophenol, 2,4,6-tribromophenol, chlorobenzene, and toluene as the primary organic by-product pollutants. A coagulation-centered three-step approach was established for TBBPA industrial wastewater treatment. The initial step involves acidification treatment to exploit the reduced solubility of 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,6-tribromophenol under acidic conditions, with the optimal pH determined as 2.7–3.1. An acid-activated montmorillonite coagulant (AMC), prepared through roasting and high-pressure acid leaching, exhibits a distinctive "Core-shell" structure, contributing significantly to the combined coagulation and adsorption mechanism. The acid-soluble aluminum salts in AMC form positively charged flocs, electrostatically attracting negatively charged organic compounds in the wastewater. Simultaneously, the porous insoluble silicon framework displays strong adsorption capacity for pollutants. The removal efficiencies for toluene, chlorobenzene, 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,6-tribromophenol reached 88.2%, 89.1%, 88.8%, 87.1%, and 89.4%, respectively. Elemental analysis reveals that the coloration of the wastewater stems from complexation reactions between phenolic compounds and Fe3+, originating from the corrosion of iron or steel reaction vessel. Post-treatment with cation exchange resin resulted in removal efficiencies of 5.2%, 59.1%, 80.2%, 77.9%, and 88.3% for the five substances, respectively. This study outlines a crucial pathway for the effective purification of TBBPA wastewater.

Elucidating metal composition–coking relationships and coke formation pathways during gas-phase oxydehydration of glycerol over clay mineral-supported Mo-V-O catalysts

Catalyst deactivation by carbon deposition (coking) remains a major obstacle in many important industrial processes, such as catalytic gas-phase oxydehydration of glycerol. Understanding the chemical nature and development of coke species during the time-on-stream (TOS) of the catalytic solids is therefore crucial for mitigating the extent of coking and in the design of regeneration process of the coked catalysts. In this study, multiple analytical techniques, including SEM, XRD, FTIR, Raman, GC-MS, XPS, and 13C solid-state MAS NMR were employed to gain insights into the coking behavior of acid-activated montmorillonite (HMMT) supported Mo-V-O catalysts with modulated metal ratios, along with soluble and insoluble coke compositions and their evolution over time. Insoluble coke was comprised of polycyclic aromatic compounds with 5 or more fused-benzene rings containing different types of oxygen-bonded groups, such as −OCH3, −COOH, −CHO, and −OH. The major chemical constituents of soluble coke were mononuclear aromatic derivatives (i.e., xylenes, 2,4-di-tert-butylphenol, and 1-hydroxycyclohexyl phenyl ketone) and paraffinic hydrocarbons with 12–18 carbon atoms. The latter coke species is thought to be formed via the deoxygenation of linear oligoglycerols. The insights presented in this study may aid in understanding the carbon deposition process during gas-phase oxydehydration of glycerol for improved design of supported Mo-V-O catalyst materials with high coking resistance.

Acid-activated natural zeolite and montmorillonite as adsorbents decomposing metsulfuron-methyl herbicide

Modern technologies of intensive crop production demand a wide application of various types of pesticides. The adverse effect of cropping intensification is that toxic organic compounds, in particular herbicides of the sulfonylurea family, are accumulated in the soil. The herbicide metsulfuron-methyl is soluble in water and accumulates in soil moisture, causing a toxic effect on plant development. The work examines the issue of the chemical stability of metsulfuron-methyl in a model aqueous environment for the targeted selection of a mineral that adsorbs the herbicide and simultaneously catalyzes the process of herbicide hydrolysis. Degradation processes of sulfonylurea herbicide metsulfuron-methyl in aqueous media in the presence of natural zeolite, acid-activated natural zeolite, and montmorillonite К10 were investigated. Under conditions of static contact of the adsorbents with an herbicide aqueous solution, montmorillonite was more active in the sorption and degradation of metsulfuron-methyl. During the first 1–2 days the herbicide concentration decreased by a factor of 5. An almost complete degradation of metsulfuron-methyl in aqueous dispersions of the acid-activated zeolite and montmorillonite was attained within 20 days. Pore size distribution functions (Barrett-Joyner-Halenda and standard non-local density functional theory methods) were evaluated. The acid treatment of the natural zeolite changed its porous structure - its specific surface area grew by a factor of 5. Three fractions of mesopores 4–10, 10–20, 20–30 nm were revealed in the original zeolite, and one fraction of pores 2.0–3.5 nm was found in the acid-activated zeolite. In the montmorillonite, only one group of 3–15 nm pores was detected. Studies of structural changes in natural zeolite after acid modification were carried out using the methods of X-ray fluorescence and X-ray phase analysis, scanning electron microscopy and infrared spectroscopy. The acid-activated montmorillonite and natural zeolite show promise for land reclamation work on detoxification of soils contaminated by sulfonylurea herbicides.

Regulation of acidity and basicity of oxide/montmorillonite catalysts for selective dehydration of monoethanolamine to ethylenimine

The heterogeneous dehydration of monoethanolamine (MEA) to ethylenimine (EI) over solid acids/bases has garnered significant attention in industry because of the importance of EI in fine chemical engineering and the advantage in product separation. Unfortunately, lacking insight into the impacts of acidity/basicity on product selectivity in the reaction hinders the development of high-performance solid acids/bases. To investigate the effect of acidity/basicity, this work employs acid-activated montmorillonite (Acid-MMT) as catalyst and the acidity/basicity is adjusted by adding different acidic/basic oxides and changing preparation conditions. Under the conditions of reaction temperature = 420 °C, GHSV = 5000 h−1, N2/MEA = 19, the optimized Acid-MMT based catalyst modified by Cs2O and P2O5 exhibits a MEA conversion of 86.4% and an EI selectivity of 80.3%. By correlating the catalyst performance with the acidity/basicity, lower amount of acidic/basic sites leads to a higher selectivity of EI via intramolecular dehydration of MEA, while intermolecular dehydration of MEA is inhibited. This is because the intermolecular dehydration reaction is kinetically obstructed by the low acidic/basic amounts, and the parallel intramolecular dehydration reaction becomes kinetically dominated. Furthermore, the catalytic results and the statistical study demonstrate that more balanced amounts between acidic and basic sites favor the intramolecular dehydration reaction. Therefore, we can obtain an effective Cs-P/Acid-MMT catalyst for the selective dehydration of MEA to EI, and propose some solid evidences about the effect of acidity/basicity on product distribution in MEA dehydration over the solid acids/bases.

Bifunctional acid-activated montmorillonite catalyzed biodiesel production from non-food oil: Characterization, optimization, kinetic and thermodynamic studies

Utilizing robust heterogeneous catalysts to efficiently produce biodiesel from low-cost non-food oil is very important for replacing fossil energy to meet globally increasing energy demands and accelerate realization of carbon neutrality. In this study, a novel Lewis (L)-Brønsted (B) bifunctional catalytic material 30%Sn-MMT-SO3H was conveniently fabricated by ion-exchange and sulfonation using widely-sourced and biocompatible montmorillonite (MMT) as a matrix, which was successfully applied in direct conversion of Jatropha curcas oil (JCO) into biodiesel. Systematical characterization techniques showed that 30%Sn-MMT-SO3H presented a layered nanostructure along with a high specific surface area (145.32 m2/g), rich mesopores (5.8 nm), strong acidic intensity (1.801 mmol g−1), abundant accessible active sites, and outstanding chemical and thermal stability. Additionally, the single-factor method and response surface methodology (RSM) were employed to investigate optimal reaction conditions. Accordingly, the maximum biodiesel yield (93.1%) was achieved under conditions of 7 wt% catalyst dosage, 20.2 methanol/oil molar ratio at 150 °C for 7.5 h, and no significant decrease was observed after five cycles. Importantly, kinetic and thermodynamic behaviors together with possible reaction mechanisms were also determined. Compared with other reported catalysts, 30%Sn-MMT-SO3H exhibited satisfactory activity and reusability, showing promising prospects in industrialization of biodiesel mediated by heterogeneous acid catalysts.

Eco-friendly CO2 adsorption by activated-nano-clay montmorillonite promoted with deep eutectic solvent

ABSTRACT In this work, an innovative and environmentally friendly adsorbent for CO2 capture is synthesized by Choline Chloride-Urea (ChCl: U) functionalization of the acid-activated montmorillonite (MMT) for the first time. The surface area enhancement was achieved by acid activation at 3 Molarity, which resulted in 7.1 and 10.9 times increase in the specific area and pore volume, respectively. In fact, the highest reported value of the surface area of montmorillonite has been achieved. The characterization was carried out by FTIR, BET, XRD, and SEM to ensure the qualification of the modified acid-activated and then impregnated with the solvent. The optimum condition for the input variable was 30 ºC, 9 bar, and 50% of the solvent to MMT, where the response was 252 mg/g. The evaluation of the heterogeneous and mono-multilayer adsorption indicated the experimental data well-fitted to the Hill isotherm model with n higher than 1, indicating the desirability of the adsorbent (n was also 1.59 for the Freundlich isotherm model). The Elovich kinetic model was observed to be in the best agreement with the experimental data. Eight cycles of adsorption-desorption results indicated an excellent reversible adsorbent with low-temperature regeneration (90ºC) is attained.

Recent advances in engineering montmorillonite into catalysts and related catalysis

ABSTRACT Montmorillonite, a ubiquitous clay mineral, has been engineered into a variety of porous and nanostructured catalysts, owing to its peculiar layered structure with characteristic surface and intercalation chemistry. Such a class of catalysts have continuously received considerable attention in both science and industry. This review examines recent advance in engineering montmorillonite into metal ion-exchanged montmorillonite catalysts, acid-activated montmorillonite catalysts, organo-montmorillonite catalysts, pillared interlayered montmorillonite catalysts and montmorillonite-supported catalysts. The former two types of montmorillonite-based catalysts have been used in the catalytic cracking, dehydration, hydrolysis, esterification, polymerization, alkylation, and Fischer-Tropic synthesis. The introduction of oxide pillars in the interlayer space of montmorillonite and the immobilization of metal oxides or zero-valent metals on the surface of montmorillonite allow montmorillonite to be used in the catalytic oxidation, reduction, isomerization and coupling reactions. Currently, the role of montmorillonite in acid catalysis, redox catalysis, and free radical catalysis have been partly revealed. The effect of the structures and the active sites of modified montmorillonite on its catalytic performance need to be investigated in more detail. Future work is suggested to focus on solving engineering problems and exploring novel catalytic applications of montmorillonite, in particular exfoliated montmorillonite nanolayers.

Fe doped-CoB catalysts with phosphoric acid-activated montmorillonite as support for efficient hydrogen production via NaBH4 hydrolysis

In this study, montmorillonite (MMT) clay was modified with different acids to be used as support material. The modified MMT clay was used to obtain hydrogen in the hydrolysis reactions of NaBH4 (NaBH4-HR) as a support material for the Co–B and Co–Fe–B catalyst. During the activation of MMT clay, the effects of different acids, phosphoric acid (H3PO4) concentration, and impregnation time with H3PO4 were investigated. During the hydrogen generation from the NaBH4-HR, effects of Co loading, Fe loading, NaBH4 concentration, temperature and, catalyst durability were investigated. The maximum HGRs for MMT-H3PO4–CoB and MMT-H3PO4–Co–Fe–B treated with 5 M H3PO4 for 7 days were 1869 and 4536 mL/min/gcatalyst, respectively. The activation energies for MMT-H3PO4–CoB and MMT-H3PO4–Co–Fe–B catalyst samples were 49.5 and 38.90 kJ/mol.

Zinc supported on acid-activated montmorillonite for aromatization reactions

AbstractA Na-montmorillonite (Na-MMT) was activated with HNO3 (20 wt.%) solution at various temperatures and times to obtain acid-activated MMT (Acid-MMT). Zinc (4 wt.%) was supported on Acid-MMT via the impregnation method using Zn(NO3)2⋅6H2O as a precursor. The catalytic performance of the Zn/Acid-MMT for the aromatization of heptane was investigated. The amount and distribution of acidity of Acid-MMT, which could be adjusted by changing the acid activation time and temperature, significantly affected the heptane conversion and aromatics content. As a result, an efficient Zn/Acid-MMT catalyst for the aromatization reaction was obtained by optimizing the acid-treatment conditions of Na-MMT.

Practical and inexpensive acid-activated montmorillonite catalysts for energy-efficient CO2 capture

Acid-activated montmorillonite catalysts were prepared and tested for optimizing CO2 desorption from CO2-rich amine solutions, eventually for energy-efficient CO2 capture.

Ruthenium-doped Titania-pillared Clay for The Selective Catalytic Oxidation of Cyclohexene: Influence of Ru Loading

A series of ruthenium-based catalysts supported on acid-activated montmorillonite (PILC) and interspersed with titanium (Ru/Ti-PILCs) were prepared with various amounts of ruthenium. Their catalytic performances in the selective oxidation of cyclohexene, using tert-butylhydroperoxide (TBHP) as oxidant were checked. The clay structure modification by acid activation and impregnation of transition metals resulted in an enhanced Lewis and Bronsted acidities. The Ru/Ti-PILCs materials were characterized using X-ray diffraction (XRD), surface area and pore volume measurements, surface acidity followed by Fourier transform infrared (FTIR) spectroscopy, chemical analysis, and Scanning Electron Microscopy (SEM). It was found that all catalysts can selectively oxidize cyclohexene through allylic oxidation leading mainly to 2-cyclohexene-1-one (Enone) as the major product, and 2-cyclohexene-1-ol (Enol) as secondary product. With the 5 %Ru/Ti-PILC, it was possible to reach 59 % cyclohexene total conversion, and 87 % selectivity into 2-cyclohexene-1-one and 13 % selectivity into 2-cyclohexene-1-ol.

Facile synthesis of protonated g-C3N4 and acid-activated montmorillonite composite with efficient adsorption capacity for PO43− and Pb(II)

A novel protonated graphite carbon nitride and acid-activated montmorillonite (g-C3N4/Mt) composite was prepared and evaluated its removal efficiency for PO43− and Pb(II) from aqueous media. The as-prepared composite was characterized by XRD, FT-IR, TG, XPS, SEM, BET and Zeta potential. Batch experiments were carried out under various conditions such as the amount of adsorbent, initial adsorbate concentration (Co), solution pH, temperature, and contact time. 2.0%-g-C3N4/Mt presented maximum adsorption capacity for PO43− and Pb(II) as compared to single g-C3N4, Mt or other synthesized composites. The removal efficiency of the as-prepared composite (2.0%-g-C3N4/Mt) was significantly elevated owing to the synergistic effects and the saturated adsorption capacities of PO43− and Pb(II) on 2%-g-C3N4/Mt was 5.06mg/g and 182.7mg/g respectively. While the saturated adsorption capacity of bare g-C3N4 was only 1.56mg/g and 22.3mg/g for PO43− and Pb(II) respectively, and bare Mt showed adsorption capacity of 0.65mg/g and 124.2mg/g for PO43− and Pb(II) respectively. The adsorption process for both contaminants showed well-fitting with the pseudo-second-order kinetic model, and the adsorption isotherm for both contaminants followed the Langmuir model. The thermodynamic study suggested that the adsorption of Pb(II) was a spontaneous and endothermic process.

Formulation and antibacterial properties of clay mineral-tetracycline and -doxycycline composites

Clay minerals have been used as adsorbents for decades but research into their use within healthcare as drug-carriers and modified drug release materials is an increasingly common area of interest. In current clinical practice the management of acute bacterial skin and skin-structure infections (ABSSSIs) requires patients to take systemic antibacterial treatment due to a lack of appropriate topical options. In this research tetracycline (TC) and doxycycline (DC) were adsorbed onto a range of clay minerals (kaolinite, montmorillonite, acid-activated montmorillonite, Laponite® RD and Laponite® XL21) to evaluate their potential as materials for the delivery of these antibiotics to infected wounds. A dispersion pH that favoured the zwitterionic form of the antibiotic molecules was shown to favour adsorption onto the clay minerals. FTIR and pXRD showed that positively charged groups on the antibiotic molecules interacted with the negatively charged clay mineral surface, whilst negatively charged groups on the antibiotic molecules could interact with the positively charged edge-sites of the clay minerals. Swelling clays such as the two Laponites® were able to adsorb much more TC and DC due to their structure and chemistry. The clay minerals alone did not have any antibacterial effects against Staphylococcus epidermidis, Cutibacterium acnes, and Pseudomonas aeruginosa. Antibiotic containing composites successfully released TC and DC, exhibiting activity against the three bacterial strains proportional to the antibiotic-loading on the composites. This research demonstrates the ability of these clay minerals to deliver TC and DC against common skin pathogens and their potential for future development towards clinical applications.

Strongly proton exchanged montmorillonite K10 (H+-Mont) as a solid acid catalyst for highly efficient and environmental benign synthesis of biscoumarins via tandem Knoevenagel–Michael reaction

In this study, synthesis of micro/meso porous acid-activated montmorillonite K10 (H+-Mont) was carried out by the activation of Na+-montmorillonite with HCl (4 M) at the controlled conditions. The prepared H+-Mont clay was then characterized using FT-IR, SEM, EDX, XRD and BET analyses. SEM and BET surface analyses represented that by the acid-activation, adjacent layers of montmorillonite K10 (Mont K10) were exfoliated to tiny segments leading to raise of surface area and total pore volume in H+-Mont system rather than the alone Mont K10. Catalytic activity of the prepared H+-Mont clay was further studied as a potent solid acid catalyst for synthesis of biscoumarin materials via tandem Knoevenagel–Michael reaction of 4-hydroxycoumarin with aromatic aldehydes. All reactions were carried out in a mixture of H2O-EtOH (1:1) at room temperature to afford the products in high to excellent yields within 25–50 min.

N-Hexane Isomerization in the Presence of Nanodispersed Catalysts Supported on Acid-Activated Montmorillonite in the Sodium Form

Catalysts based on a palladium sol supported on acid-activated montmorillonite in the Na form (Pd-sol/NaHMM) have been tested in the n-hexane isomerization reaction. An increase in the Pd content from 0.1 to 0.35% leads to an increase in the catalyst activity. The C6+ isomer selectivity remains stable and fairly high: it is 94.6–98.0% in the presence of the catalysts with a Pd content of 0.1 or 0.35%, respectively. The maximum conversion of n-hexane over the 0.35%Pd catalyst is 52.6% at a temperature of 400°C; the addition of mordenite leads to a slight decrease in conversion to 50.9%. The maximum conversion at 400°C in the presence of the 0.1%Pd catalyst and the mordenite-modified catalyst is 45.0 and 50.4%, respectively. The maximum yield of isomeric hexanes over the zeolite-free 0.35%Pd and 0.1%Pd catalysts is 44.9 and 39.3%, respectively. In the presence of the mordenite-containing 0.35%Pd/NaHMM+HM catalyst and the low-percentage 0.1%Pd/NaHMM+HM catalyst, the C6 isomer yield is 44.3 and 43.0%, respectively. The amount of hydrocracking products does not exceed 0.7%. The particle size of the Pd sols is 3.5–5 nm, as determined on a JEM 2100 high-resolution transmission electron microscope. The elemental composition of the Pd-sol/NaHMM catalysts containing different amounts of palladium and the catalysts modified with mordenite has been determined by energy dispersive X-ray fluorescence spectroscopy.

Immobilized copper-layered nickel ferrite on acid-activated montmorillonite, [(NiFe2O4@Cu)(H+-Mont)], as a superior magnetic nanocatalyst for the green synthesis of xanthene derivatives.

In this study, the immobilization of copper-layered nickel ferrite on the surface and in the cavities of acid-activated montmorillonite (H+-Mont) was investigated. In this context, magnetic nanoparticles (MNPs) of NiFe2O4 as the prime magnetic cores were prepared. Next, through the reduction of Cu2+ ions with sodium borohydride, the nanoparticles of Cu0 were immobilized on the nanocore-surface of NiFe2O4, and the constituent NiFe2O4@Cu MNPs were obtained. Moreover, through the activation of montmorillonite K10 (Mont K10) with HCl (4 M) under controlled conditions, the H+-Mont constituent was prepared. The nanostructured NiFe2O4@Cu was then intercalated within the interlayers and on the external surface of the H+-Mont constituent to afford the novel magnetic nanocomposite (NiFe2O4@Cu)(H+-Mont). The prepared clay nanocomposite was characterized using FTIR spectroscopy, SEM, EDX, XRD, VSM and BET analyses. The obtained results showed that through acid-activation, the stacked-sheet structure of Mont K10 was exfoliated to tiny segments, leading to a significant increase in the surface area and total pore volume of the H+-Mont constituent as compared to those of montmorillonite alone. SEM analysis also exhibited that the dispersion of NiFe2O4@Cu MNPs in the interlayers and on the external surface of acid-activated montmorillonite was carried out successfully, and the nanoparticle sizes were distributed in the range of 15–25 nm. The BET surface analysis also indicated that through the immobilization of NiFe2O4@Cu MNPs, the surface area and total pore volume of the H+-Mont system were decreased. The catalytic activity of (NiFe2O4@Cu)(H+-Mont) was further studied towards the synthesis of substituted 13-aryl-5H-dibenzo[b,i]xanthene-5,7,12,14(13H) tetraones 3(a–k) and 3,3,6,6-tetramethyl-9-aryl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H) diones 5(a–k)via the pseudo-one-pot three-component cyclocondensation of 2-hydroxy-1,4-naphthoquinone (Lawsone)/dimedone and aromatic aldehydes in a mixture of H2O–EtOH (1 : 1 mL) as a green solvent at 80–90 °C. The (NiFe2O4@Cu)(H+-Mont) MNPs can be easily separated from the reaction mixture by an external magnetic field and reused for seven consecutive cycles without significant loss of catalytic activity.

Ni0 NPs anchored on acid-activated montmorillonite (Ni0-Mont) as a highly efficient and reusable nanocatalyst for synthesis of biscoumarins and bisdimedones

Ni0 nanoparticles were immobilized on acid-activated montmorillonite (Ni0-Mont) by anchoring Ni(OAc)2·4H2O on modified micro/mesoporous montmorillonite followed by reduction with ethylene glycol. The prepared clay composite system was then characterized using Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD) analysis, and Brunauer–Emmett–Teller (BET) analysis. SEM analysis revealed perfect dispersion of metallic nickel nanoparticles with size distribution of 6‒41 nm on the clay matrix. Micro/mesoporous montmorillonite was prepared by activation of Na+-montmorillonite with HCl (4 M) under controlled conditions. The catalytic activity of the prepared Ni0-Mont clay was studied in one-pot microwave-assisted synthesis of biscoumarins and bisdimedones via Knoevenagel reaction of aromatic aldehydes with 4-hydroxycoumarin or dimedone in solvent-free conditions. All reactions were carried out at room temperature within 5‒15 min (for biscoumarins) and 5–20 min (for bisdimedones) to afford the products in high to excellent yield. The reusability of the Ni0-Mont catalyst was also investigated in seven consecutive cycles, without significant loss of catalytic activity.

Improved waste-sourced biocomposite for simultaneous removal of crude oil and heavy metals from synthetic and real oilfield-produced water.

Oil- and gas-produced water (PW) which contains various pollutants is an enormous threat to the environment. In this study, a novel low-cost bio-adsorbent was prepared from shrimp shell and acid-activated montmorillonite. The results of FT-IR spectroscopy, energy dispersive X-ray (EDX) analysis, and SEM-EDX technique indicated that the chitosan-activated montmorillonite (CTS-A-MMT) was prepared successfully. The synthesized CTS-A-MMT was applied to remove simultaneously five cationic and anionic metal species and crude oil from synthetic and real oilfield PW. The adsorption data indicated that crude oil and all studied metals (except As) were adsorbed to CTS-A-MMT in a monolayer model (best fitted by Langmuir model), while As adsorption fits well with Freundlich model. Kinetic models' evaluation demonstrated that the adsorption kinetics of metals on CTS-A-MMT are initially controlled by the chemical reaction (film diffusion) followed by intra-particle diffusion. Application of the prepared CTS-A-MMT in real oilfield PW indicated removal efficiency of 65 to 93% for metals and 87% for crude oil in simultaneous removal experiments. Presence of additional ions in PW decreased the removal of studied metals and crude oil considerably; however, the concentration of the investigated pollutants in treated PW is less than the ocean discharge criteria. It is concluded that the prepared CTS-A-MMT composite is a low-cost and effective adsorbent for treating wastewater contaminated with crude oil and heavy metals (i.e., PW).

Turning Biodiesel Waste Glycerol into 1,3-Propanediol: Catalytic Performance of Sulphuric acid-Activated Montmorillonite Supported Platinum Catalysts in Glycerol Hydrogenolysis

Direct C-O hydrogenolysis of bioglycerine to produce 1,3-propanediol selectively is a vital technology that can expand the scope of biodiesel industry and green chemical production from biomass. Herein we report sulphuric acid-activated montmorillonite clay supported platinum nanoparticles as highly effective solid acid catalysts for the selective production of 1,3-propanediol from glycerol. The catalytic performances of the catalysts were investigated in the hydrogenolysis of glycerol with a fixed bed reactor under ambient pressure. The results were found promising and showed that the activation of montmorillonite by sulphuric acid incorporated Brønsted acidity in the catalyst and significantly improved the selectivity to 1,3-propanediol. The catalytic performance of different platinum loaded catalysts was examined and 2 wt% Pt/S-MMT catalyst presented superior activity among others validating 62% 1,3-propanediol selectivity at 94% glycerol conversion. The catalytic activity of 2Pt/S-MMT was systematically investigated under varying reaction parameters including reaction temperature, hydrogen flow rate, glycerol concentration, weight hourly space velocity, and contact time to derive the optimum conditions for the reaction. The catalyst stability, reusability and structure-activity correlation were also elucidated. The high performance of the catalyst could be ascribed to well disperse Pt nanoparticles immobilized on acid-activated montmorillonite, wider pore-structure and appropriate acid sites of the catalyst.