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Energy crises and water pollution have become the key challenges in current era of technology. In this research work, activated carbon modified BiVO4 photocatalysts have been prepared using simple hydrothermal methods for efficient hydrogen evolution through water splitting under visible light irradiation and degradation, simultaneously. The properties of the synthesized photocatalysts were studied through SEM, UV, XRD, BET and PL emission spectroscopy. The 4%AC/BiVO4 exhibited highest degradation efficiency ≈98% in 60 min and production of hydrogen energy ≈510 h−1g−1 which is much higher when compared to pure BiVO4. The enhancement in the efficiency was due to large surface area, large absorption region. High crystallinity, small band gap and synergetic effect between the composites. The activated carbon based BiVO4 composites showed high stability which shows its vital role in practical applications.

In this paper, the bismuth vanadate and the composite of bismuth vanadate BiVO4 with nickel ferrite BiVO4/NiFe2O4 is aimed to be synthesized using hydrothermal method for the effective degradation of methylene blue. The concentration of nickel ferrite is varied from 1 to 5%. The morphological, structural, and the optical properties of the prepared samples are studied using X-ray diffraction (XRD), Scanning electron microscope (SEM), Photoluminescence (PL) spectroscopy, and Ultra-violet (UV) spectroscopy. The photocatalytic activity of the prepared photocatalyst is performed under visible light. The composite of BiVO4/NiFe2O4 4% efficiently degrade 99% of methylene blue after 90 min from 100-ml solution under visible light. This paper explains the synthesis of bismuth vanadate and it is composite with nickel ferrite BiVO4/NiFe2O4 and give information about the structural and morphological of these synthesized materials.

The discharge of various textile effluents into water is provoking numerous ecological issues that have become severe threat to human beings and aquatic lives. The removal of the effluents by photodegradation using appropriate nanoparticles (NPs) is the most promising remediation process. In this study, a facile hydrothermal approach is utilized to fabricate pure ZnO and strontium doped ZnO nanoparticles (Sr-ZnO). The fabricated nanoparticles represented hexagonal morphology and structure which was controlled with the strontium doping. The optical properties of fabricated NPs were also controlled and approached to visible light (2.52 eV) instead of the UV light. The fabricated NPs were employed for photodegradation of Rhodamine B (RHB) dye from polluted wastewater and further effect of factors like light irradiation time, pH, photocatalyst dose, dye concentration etc. was also explored to optimize the parameters. Sr-ZnO photocatalyst represent excellent RHB dye degradation as well as cyclic stability with pseudo first order kinetics. The current study proves the suitability of Sr-ZnO photocatalyst under visible light irradiation for treatment of the organic and dye polluted wastewaters.

The concern to reduce global carbon emissions has significantly improved the development of efficient solid sorbents such as activated carbon (AC). In this study, AC is developed from date stones which is one of the abundantly found agricultural waste material in gulf region. The AC was completely characterized in terms of pore volume, surface area, stability test, volatile carbon and fixed carbon contents. Impregnation of AC was performed by three different alkanolamines, namely Diethylene triamine (DETA), Pentaethylene hexamine (PEHA) and Di-ethanol amine (DEA). The alkanolamine impregnated sorbents were utilized for CO2adsorption at temperatures of 25, 30, 40, 50, 60, 70 and 100 °C and carbon dioxide (CO2) concentrations of 10, 30, 50, 70 and 92% in helium. The adsorption phenomenon was evaluated by Langmuir isotherms for all the studied adsorbents. The AC developed from date stones provided high adsorption loading capacity of CO2 i.e., 89.79 mg/g of AC at 25 °C. Thermodynamic parameters showed that the adsorption was endothermic and spontaneous in nature. Moreover, desorption profiles reveal that DETA-AC samples provided most favorable characteristics with respect to the value of desorption constant.

Mg–Fe Layered Double Hydroxide (LDH) with M2+: M3+ 3:1 stoichiometric ratio was synthesized and employed as catalyst precursor for COx-free hydrogen production from ammonia. The resulting catalyst showed good catalytic activity. A series of Mg/Co–Fe layered double hydroxides were synthesized by replacing Mg2+ with Co2+ without disturbing M2+:M3+ ratio. The influence of nature and extent of Co(II) substitution on structure, morphology and surface properties were studied. A systematic study was carried out using these materials as catalyst precursors for ammonia decomposition. BET, XRD, TPR, XPS, CO2-TPD and TEM techniques were used to characterize the synthesized catalysts. These Fe-based catalysts are highly active, highly stable and not promoting any stable surface nitridation during the ammonia decomposition reaction. Among all catalysts, the Mg3Co3Fe2 catalyst showed the highest activity i.e. 100% conversion at 6,000 h−1 and 60% at 50,000 h−1 space velocities at 550 °C. The registered superior catalytic activity was result of the formed specific catalyst's properties like high surface area, high surface Co and Fe atomic concentration and suitable basicity. These Fe-based materials are, cost-effective, easily synthesize and highly stable, thus attractive for large-scale operation.

In this study, the densification of three agriculture waste biomasses (corn cobs, cotton stalks, and sunflower) is investigated using the torrefaction technique. The samples were pyrolyzed under mild temperature conditions (200–320 °C) and at different residence times (10 min–60 min). The thermal properties of the obtained bio-char samples were analyzed via thermo-gravimetric analysis (TGA). Compositional analysis of the torrefied samples was also carried out to determine the presence of hemicellulose, cellulose, and lignin contents. According to the results of this study, optimum temperature conditions were found to be 260 °C–300 °C along with a residence time of 20 min–30 min. Based on the composition analysis, it was found that biochar contains more lignin and celluloses and lower hemicellulose contents than do the original samples. The removal of volatile hemicelluloses broke the interlocking of biomass building blocks, rendering biochar brittle, grindable, and less reactive. The results of this study would be helpful in bettering our understanding of the conversion of agricultural waste residues into valuable, solid biofuels for use in energy recovery schemes. The optimum temperature condition, residence time, and GCV for torrefied corn cobs were found to be 290 °C, 20 min, and 5444 kcal/kg, respectively. The optimum temperature condition, residence time, and GCV for torrefied cotton balls were found to be 270 °C, 30 min, and 4481 Kcal/kg, respectively. In the case of sunflower samples, the mass yield of the torrefied sample decreased from 85% to 71% by increasing the residence time from 10 min to 60 min, respectively.

Silver catalysts supported on ceria-zirconia (CZ) mechanically mixed oxide were synthesized by wet impregnation and chelating methods. Nominal loadings of 5 wt.% of Ag was deposited on the CZ support. These catalysts were tested for the CO2 hydrogenation reaction to methanol with feed gas composition of CO2–H2 = 3:1 at 250 °C, 20 bar total pressure and GHSV of 1800 h−1. The calcined and reduced catalysts were characterized using XRD, BET, TPR, SEM-EDS, XPS and FTIR-DRIFTs techniques. Finely deposited silver crystallites sized in the range of 20–50 nm were observed through SEM and HR-TEM analysis. TPR and XRD studies demonstrated the presence of Ag2O and metallic silver (Ag0) on CZ support. About 10% of CO formation was observed on chelating catalyst (5Ag/CZ CHE). However, only, 5% CO was observed on impregnated (5Ag/CZ IMP) catalyst. The greater CO formation was associated with ease reduction of Ag2O to metallic silver in 5Ag/CZ CHE catalyst. Further, 70% of methanol selectivity was observed on 5Ag/CZ IMP due to the presence of Ag2O on CZ. FTIR-DRIFTs results revealed the methanol formation via formate intermediates and CO formation via RWGS reaction on the studied catalysts.

The influence of Pd loading was studied for the gas phase catalytic hydrodechlorination of 1,2,4-trichlorobenzene over Pd supported on Mg-Al mixed oxide support with Mg:Al ratio 2:1. The Mg-Al support was prepared from hydrotalcite precursor. A series of catalysts was prepared with different loadings of Pd (1–6 wt%) on Mg-Al mixed oxide support. The performance of catalytic material was evaluated at different temperatures ranging from 425–575K. The fresh and used catalysts were characterized with different analytical techniques such as BET surface area, X-ray diffraction studies, Temperature programmed reduction, X-ray photoelectron spectroscopy and CO-chemisorption studies. H2-Temperature programmed desorption studies was also performed to understand the metal-support interaction and suitable active sites. The 4wt% of Pd on Mg-Al mixed oxide catalyst showed the highest conversion and selectivity among all catalysts and maintained steady activity with 10 h of time-on-stream studies. The main reasons for high activity are suitable metal-support interactions, Pd particle size, high surface area, and high surface Pd atomic concentration. The influence of Pd loading was studied for gas phase catalytic hydrodechlorination of 1,2,4-trichlorobenzene over Pd supported on Mg-Al mixed oxide support with Mg:Al ratio 2:1. The different Pd-loadings in catalyst was studied for hydrodechlorination. The 4wt% of Pd on Mg-Al mixed oxide catalyst showed the highest performance among all the catalysts.

The La based perovskite type LaMO3 (M=Ni, Co) oxides were prepared by combustion synthesis method using citric acid as organic fuel. These catalyst precursors tested for ammonia decomposition. The LaNiO3 and LaCoO3 catalysts showed good activity for NH3 decomposition. The LaNiO3 catalyst displayed greater activity than LaCoO3. This due to high surface area and easily reducibility of Ni species. A 50% of La was substituted by Ce in both LaNiO3 and LaCoO3 catalysts. A remarkable effect on catalytic performance was observed with the partial substitution of La by Ce in perovskite catalyst especially at lower temperatures. The La0.5Ce0.5NiO3 catalyst exhibited highest activity among all prepared samples. The achieved superior activity is due to boost in surface area, reducibility and suitable basicity. The SEM elemental mapping of La0.5Ce0.5NiO3 catalyst concluded that metal oxide constituents dispersed homogeneously. The La0.5Ce0.5NiO3 catalyst showed excellent stable catalytic performance during 50h time on study at 550°C.

Alumina (Al), alumina-boron (Al-15B), alumina-boron-antimony (Al-B-Sb) and alumina-antimony (Al-15Sb) catalysts were synthesized by sol-gel method using ethanol as a solvent and ammonia gas as a gel forming agent. These catalysts were studied for the dehydrogenation of ethylbenzene (EB) to styrene in the presence of oxygen and steam. The reaction was carried out in the temperature range of 450-500 °C with EB contact time 0.54 gcat.s/cm3. The synthesized catalysts were characterized by using N2-physisorption, XRD, XPS, TEM-HRTEM-EDS and NH3-TPD-mass spectral analysis techniques. At 475 °C, only 58% of styrene selectivity with 32% of EB conversion was observed on Al. Addition of 15 mol.% of B to Al significantly enhanced the selectivity of styrene to 94% with 46% EB conversion at 475 °C. Addition of 15 mol.% Sb to Al reduced the EB conversion (38%) and styrene selectivity (75%) compared to Al-15B catalyst. Interestingly, small amount of Sb (5 mol.%) addition to Al-B improved the EB conversion to 52.5% with 92% of styrene selectivity at 475 °C. The acid sites of weak and moderate strength were increased in Al-15B catalyst compared to Al. Boron played a dual role as Al densification suppressing agent and to some extent deposited on the surface of Al which improved the styrene selectivity. However, small amount of Sb addition to Al-15B not only retained weak and moderate strength acid sites of Al-B but also generated acid sites of Sb which led to the formation of N2O and NO during NH3-TPD-mass analysis. Hence, the styrene yield (48.8%) was improved on Al-B-5Sb compared to Al-15B catalyst (43%). It is noteworthy that Al-15B and Al-B-5Sb catalysts were stable for more than 60h of reaction.

Water contamination caused by the organic pollutants and microorganism is the serious risk towards the human life and aquatic ecosystem that can be addressed by active and environment-friendly nanoparticles. In current work, Zinc oxide nanoparticles (ZnO-NPs) have been synthesized first time by utilizing leaves extract of Citrus reticulata via facile, cost effective and ecofriendly green approach. Moreover, the influence of leaves extract concentration on properties of synthesized nanoparticles was also inspected. Various characterization techniques results affirmed that the synthesized ZnO-NPs have hexagonal crystalline structure with size range of 43.05–30.67 nm and band gap of 3.26–3.15 eV. Variation in the leaves extract concentration affected the morphology and optical properties of the green synthesized NPs. Further, the synthesized ZnO-NPs were employed as a photocatalyst for photodegradation of Rhodamine B dye. ZnO-NPs were also employed as antibacterial agent against gram-positive (S. aureus) and gram-negative (E. coli) bacteria where they exhibited appreciable antibacterial activity. Therefore, the novel, facile and green synthesized ZnO-NPs are promising for simultaneous removal of organic pollutants and bacteria from polluted water.

The contamination of ammonia in surface water should be given a critical outlook as it easily exceeds the regulated standard limit especially in rivers located in many parts of the world. Several conventional methods for the removal of ammonia have been widely used but its effectiveness in removing ammonia is not impressive. Membrane technology is gaining wider application in removal of nitrogen compounds from water and wastewater. In this study, polyvinylidene fluoride (PVDF) flat sheet membrane incorporated with adsorbent material (zeolite and gypsum) were fabricated to study its efficiency in ammonia removal. The morphology of the blended PVDF membrane by using both additive materials showed that some changes were observed at the bottom layer of the membrane where an extremely wide finger-like structure has been formed. This modified membrane exhibits hydrophobicity properties with contact angle value of 89.0 ± 0.48° and 96.3 ± 0.54° for zeolite and gypsum, respectively. Meanwhile, the crystallinity of the fabricated membrane increases from 20% for pure PVDF to 25.9% and 26.4% for the respective additive of gypsum and zeolite. Furthermore, a comparable separation performance was obtained for the blended membrane with the pure PVDF and the commercial membrane of NF1. Thus, the presence of zeolite or gypsum in the synthesized PVDF membrane could potentially enhance the removal of ammonia by becoming an adsorption material as it commonly functions.

This work deals with the effect of catalyst preparation method of the mixed Co, Mg and La oxide catalysts on their structure and catalytic properties for ammonia decomposition. Two methods are used for catalysts preparations impregnation and co-precipitation (in air and in pure O2 atmosphere), The Mg/La = 2 molar ratio and 5 wt% of cobalt content was maintained same in all catalysts. The catalyst performance was evaluated in the temperature range 300–550 °C at atmospheric pressure. The prepared catalysts were characterized by BET, XRD, TPR, XPS, CO2-TPD and SEM techniques. No pronounced differences were observed in BET among the catalysts. It was found that the 5CML-OXY (5 wt%Co over Mg La catalyst prepared by co-precipitation method in oxygen atmosphere) has superior activity among the other catalysts. This could be attributed to availability of easily reducible cobalt species determined by TPR studies and enhanced interaction between Mg and La determined by SEM and XPS. The moderate basic site density determined by CO2-TPD results was also increased in 5CML–OXY catalysts compared with other catalysts. These consequences are might be one of the reasons for enhanced activity of 5CML–OXY catalyst compared to other catalysts. Hence catalyst preparation by co-precipitation in oxygen atmosphere is the best method which might be one of the parameters that influenced on catalytic properties of the cobalt on MgO La2O3 system, for ammonia decomposition.

Rh@UIO-66, prepared by using the double-solvent host–guest strategy and excess reduction methods, exhibited a higher catalytic activity in AB hydrolysis compared with Rh/UIO-66 because the ultrafine Rh nanoparticles were confined to UIO-66 channels. This confinement effect played a key role in enhancing the catalytic activity for AB hydrolysis.

The rapid depletion of fossil fuel resources and climatic changes has triggered the researchers' attention to find an alternative and renewable energy source. Thus, biodiesel has been recognized as a potential alternative to petrodiesel for its biodegradability, non-toxicity, and environment-friendly attributes. In this study, an efficient and recyclable Cu–Ni doped ZrO2 catalyst was synthesized and used to produce biodiesel from a novel non-edible caper (Capparis spinosa L.) seed oil. The synthesized catalyst was characterized by x-ray diffraction, fourier-transform infrared spectroscopy, scanning electron microscopy, and energy dispersive x-ray analysis. The catalyst was reused in four consecutive transesterification reactions without losing any significant catalytic efficiency. Transesterification reaction conditions were optimized via response surface methodology based on Box-Behnken design for predicting optimum biodiesel yields by drawing 3D surface plots. Maximum biodiesel yield of 90.2% was obtained under optimal operating conditions of 1:6 M ratio of oil to methanol, reaction temperature of 70 °C, reaction time of 1.5 h, and 2.5% catalyst loading. Fourier-transform infrared spectroscopy, gas chromatography–mass spectrometry, and nuclear magnetic resonance (1H and 13C) analysis confirmed the high quality of biodiesel produced from non-edible caper (Capparis spinosa L.) seed oil. The fuel properties of the produced biodiesel were also found, such as kinematic viscosity (4.17 cS T), density (0.8312 kg/L), flash point (72 °C), acid no (0.21 mgKOH/g) and sulphur content (0.00042 wt%). These properties were matched and are in close agreement with the International Biodiesel Standards of European Union (EU-14214), China GB/T 20,828 (2007), and American (ASTM6751). Thus, non-edible Capparis spinosa L. seed oil and Cu–Ni doped ZrO2 catalyst appeared to be highly active, stable, and cheap candidates to boost the future biodiesel industry.

Magnesium hydride (MgH 2 )–carbon nanotubes (CNT) composite has been prepared by high-energy ball milling method and their experimental and kinetic hydrogen adsorption studies was assessed. Hydrogen adsorption studies were performed by Sievert’s volumetric apparatus and kinetic evaluation was conducted by surface chemistry and Langmuir–Hinshelwood–Hougen–Watson (LHHW) type mode. Powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were performed. Hydrogen adsorption capacity of commercial MgH 2 , milled MgH 2 , and MgH 2 /CNT composite are found to be 0.04, 0.057, and 0.059 g (H 2 )/g (MgH 2 ) at 673 K and hydrogen pressure of 4.6 MPa. Addition of 5 wt% of CNTs to MgH 2 proved to be very critical to enhance hydrogen adsorption as well as to improve its kinetics. It was observed that hydrogen adsorption is not in quasi-state equilibrium and is modeled using kinetic rate laws.

Template-free fabrication of graphitic carbon nitride nanotubes modified with lanthanum (La/g-CNT) for dynamic photo-catalytic CO2 reduction with CH4 has been investigated. Successful fabrication of g-C3N4 nanosheets and nanotubes were obtained with enhanced photo-activity under visible-light. Using 5 wt% La/g-CNT, CO yield of 491 µmole g-cat−1 h−1 was obtained which is 3.6 and 5.9 folds higher than g-CNS and g-CN samples. Similarly, production of H2 was highest over La/g-CNT which was 2.95 folds more than g-CNT and 5.1 times higher than using g-CN. Although, pristine g-CN has more basic sites and larger BET surface area but enhanced photo-activity over La/g-CNT can be attributed to efficient transfer of electrons over 1D structure and separation of charge carriers by La. More interestingly, effect of CH4/CO2 feed ratios was obvious, whereas, highest CO was produced at CH4/CO2 ratio of 1.0 but H2 was maximum with ratio of 2.0. Among the different reaction systems, highest CO was obtained using DRM, while CO2 reduction by H2/H2O promoted both CO and CH4 production. This was obviously due to basic characteristics, sorption competition over the catalyst surface and favorable reverse water gas shift (RWSG) reaction. The stability test further confirmed the suitability of this material which prevailed until three cycles without obvious deactivation. This work will open new opportunities to develop structured nanocalaysts for solar energy based reutilization of CO2 and CH4 for the production of renewable fuels.

Oxygen defects of nanoflower TiO2 photo-catalyst was fabricated at the presence of hydrogen at different temperatures (100–600∘C) and the concentrations of oxygen defects were firstly quantitatively analyzed by hydrogen programmed temperature reduction techniques (H2-TPR). Total oxygen defect concentration and surface oxygen defect concentration were consistent with XPS and EPR results, respectively. Even at the hydrogen thermal temperature of 600∘C, the shape of TiO2 was still kept as nanoflower structure as characterized by SEM. However, the rutile and anatase coexist in the composition of crystal phase when hydrogen reduction temperature of the TiO2 catalyst reached 400∘C to 600∘C as proved by Raman and XRD results. TiO2 sample with oxygen defects shows excellent photo-catalytic activity for degradation of Direct Blue 78(DB) regardless of ultraviolet light (the maximum degradation rate achieved within 100[Formula: see text]min was 93.27%) or visible light (the maximum degradation rate achieved within 100[Formula: see text]min was 88.25%). The photo-catalytic activity seems to be highly correlated with the surface oxygen defects of TiO2 catalyst. With surface oxygen-defect concentrations increase, the degradation ability on DB was significantly enhanced, while bulk oxygen defects had negligible effect on the photo-catalytic activity. The enhanced photo-catalytic performance of TiO2 with a fixed amount of oxygen defects was attributed to the strong capturing capability of the photo-generated electrons. In addition, the surface defects could also improve the photo-catalytic reaction efficiency.

A strong synergism between Au and Mn substantially increased the catalytic activity of the Au–Mn/TOS catalyst for the complete propane oxidation as compared to the activity of mono metal Au/TOS and Mn/TOS catalysts. The high activity of Au–Mn/TOS catalyst is a result of the formation of Au 2 Mn or Au 5 Mn 2 phases and enhanced mobility of the oxygen in the support oxides. XPS, TPR, TEM and XRD studies were used to characterise the catalysts. Based on the results, a possible mechanism for the participation of the non-stoichiometric and lattice oxygen is also proposed. It is suggested that a joint effect of the Au and Mn increased the non-stoichiometric and lattice oxygen mobility of the Au–Mn/TOS catalyst, potentially being dominated by Mn.

Catalytic activity of nano-Au-catalyst(s) for the complete propane oxidation was investigated. The results showed that the nature of both Au precursor and support strongly influences catalytic activity of the Au-catalyst(s) for the propane oxidation. Oxidation state, size, and dispersion of Au nanoparticles in the Au-catalysts, surface area, crystallinity, phase structure, and redox property of the support are the key aspects for the complete propane oxidation. Among the studied Au-catalysts, theAuHAuCl4-Ce catalyst is found to be the most active catalyst.