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Mineral carbonation in aqueous solutions presents a pragmatic avenue for tackling the challenges associated with carbon capture, utilisation, and storage, particularly in limiting global temperature rise to 1.5 °C for climate change mitigation. The urgency to engineer the removal of atmospheric CO2 has driven the exploration of innovative methods for direct conversion into valuable products, with a specific emphasis on calcite as a promising approach for carbon dioxide sequestration. This investigation focuses on the biomimetic strategy of emulating the catalytic activity of carbonic anhydrase by synthesizing a zinc-based metal-organic framework. The MOF, synthesized with Zinc as the central metal coordinated by 1,2,3-benzene tricarboxylic acid, displays noteworthy structural adaptability, diversity, and an extensive surface area. The characterisation of synthesised materials through UV DRS, XRD, XPS, FTIR, SEM, and Raman analyses corroborates its structural features. A comparative study with a Nickel-based MOF (Ni-BTC-MOF) underscores the advantages of zinc over nickel in CO2 mineralisation experiments. Remarkably, Zn-BTC-MOF demonstrates superior catalytic activity, reusability, solvent compatibility, and thermal stability compared to Ni-BTC-MOF. The Zn-BTC-MOF catalyst achieves a mineralisation yield of 25 mg, comparable with the reported results for natural carbonic anhydrase (34.92 mg) and imidazole-carbonic anhydrase (21.55 mg). The Zn-BTC-MOF catalyst displays exceptional reusability, maintaining CO2 mineralisation activity across over a broad pH and temperature range. These findings underscore the potential of Zn-BTC-MOF as an effective biomimetic catalyst for carbon dioxide mineralisation, holding promising applications in carbon capture and utilization technologies. [ABSTRACT FROM AUTHOR]

In the present investigation, we report the formation of a metal–metal oxide (Zn/ZnO) nanoscale heterointerfac with concomitant hydrogen generation. The synthesis process is simple and involves the optical illumination of Zn nanoparticles (Zn(NP)) suspended in water. The concomitant hydrogen (H2) evolution during synthesis was found to be linear, and it is dependent on the growth of the Zn/ZnO nano interface. The progressively increasing amount of ZnO relative to Zn(NP) was a limiting factor in H2 evolution. Two different Zn/ZnO nanoscale heterointerfaces were created and samples were extracted at two different stages of the illumination process. The first sample, extracted from the most reactive illumination phase and named Zn(NP)/ZnO-R, had the highest hydrogen evolution reaction (HER) rate. The second sample, extracted from a less reactive illumination phase and named Zn(NP)/ZnO-S, had a lower HER rate. These in situ (solar light-induced) samples were characterized by XRD, HRTEM, and other methods. The optoelectronic features and the photoelectrochemical (PEC) investigations showed the optimal light-harvesting ability of Zn(NP)/ZnO-R and the effective separation of photoexcited charge carriers, leading to remarkable HER performance. During the visible-light-induced (in situ) conversion of Zn(NP) to Zn(NP)/ZnO-R, a concurrent HER rate of 1115 μmol h−1 was observed. Indeed, the photocurrent density value of the Zn(NP)/ZnO-R catalyst is significantly higher than that of Zn(NP)/ZnO-S, pristine Zn(NP), and ZnO. Thus, this study provides new insights into the optimal fabrication of the Zn(NP)/ZnO interface for PEC application with concomitant solar hydrogen generation. [ABSTRACT FROM AUTHOR]

In many developing and developed countries, presence of arsenite [As(III)] more than 10 ppb in groundwater is reported. Many people use the arsenic contaminated groundwater for drinking purposes, which is hazardous to human health. Hence need to be removed below the permissible level before use for drinking purpose. In this batch study, IBOA was used as an adsorbent to remove As(III) from water. From experimental data, optimal values for the dose of IBOA, time of contact and pH were found to be 1.0g/L, 24 hrs and 7.0, respectively. In this paper, ANN was applied to the various parameters and found that the results are satisfied in time study. Best fitting was found in dose study and initial concentration study where as in pH study, the ANN results and experimental results are in good agreement. In effect of coexisting ions study, ANN could not map in all cases and not shown the satisfactory results. From experimental data, it is proved that IBOA having good potential for removal of As(III) from groundwater. [ABSTRACT FROM AUTHOR]

Byline: Sadhana S. Rayalu, Nitin K. Labhsetwar Efforts are being made to develop nanomaterials for addressing issues related to energy, environment and resource conservation. In this connection, research is being conducted at Environmental Materials Unit in the area of development of nanosized structural analogues related to molecular sieves and zeolites, surface functionalised zeolites, pervoskite based catalytic materials, multifunctional metals/metal oxide materials, carbon and photocatalytically active materials. Several environmental and energy technologies have emerged with substantial benefits from nanotechnology, which include reduction in waste and improved energy efficiency, environmentally benign composite structures, waste remediation and energy conversion. Some of the key research areas include carbon capture, water-splitting reaction for hydrogen generation, biomimetic sequestration of CO2, and Diesel Particulate Filter (DPF) regeneration.

A novel low cost composite adsorbent has been successfully synthesized from waste eggshell (ES), alum, and chitin for removal of excess fluoride from drinking water. Synthesis of chitin based adsorbent (CBA) was optimized by varying different synthesis parameters such as alumina loading, ES:chitin ratio, calcination temperature, calcination time, shaking time, drying temperature, and washing time. CBA is a composite type material having heterogeneous phases of Ca(OH)2, Al(OH)3, Al2O3 encapsulated with carbon, Al(OH)3 and Al2O3 deposited on carbon and Al2O3. Presence of multiple phases with prominent presence of crystalline as well as amorphous phases of alumina has been substantiated by using XRD and SEM analysis. The elemental composition of material and EDX also suggests composite nature of material with different phases. The SEM image of CBA reveals the presence of both coarse and fine particles with irregularly shaped particles of alumina agglomerates adhering to calcite particles of ES. Defluoridation performance was systematically studied for CBA, which has outperformed several reported adsorbents with its higher adsorption capacity of 30.3 mg g−1. No significant influence on the percent fluoride removal was observed in presence of Cl− [ABSTRACT FROM AUTHOR]

Abstract: Effect of photodeposition of AuNPs (gold nanoparticles) on TiO2, CeO2, Cu2O and Fe3O4 supports has been illustrated on sacrificial donor based hydrogen evolution. The synthesized samples were characterized by diffuse reflectance spectroscopy (DRS), and transmission electron microscopy (TEM). Highest photocatalytic activity was exhibited by Au/TiO2 followed by Au/Fe3O4, Au/CeO2 and Au/Cu2O. Au/TiO2 under optimized conditions has shown significantly high photocatalytic activity under both UV–visible and visible radiation. Au/TiO2 shows hydrogen evolution rate of 920 μmol h−1 and 32.4 μmol h−1 under UV–visible and visible radiation, respectively. Significant enhancement in hydrogen evolution rate under visible light is very encouraging and may be attributed to polydispersed nature of AuNPs wherein larger particles facilitate light absorption and the smaller function as catalytic sites. Further studies are in progress to study the influence of various parameters on photocatalytic activity of Au/TiO2. [Copyright &y& Elsevier]

Highlights: [•] Au/TiO2 nanocomposites were synthesized by various routes and their photocatalytic activity was compared for hydrogen generation. [•] Under purely visible light illumination the highest hydrogen evolution of 32.4μmolsh−1 was observed in case of Au/TiO2 prepared by photodeposition. [•] The effect of photodeposition of AuNPs on different titania supports was also studied. [ABSTRACT FROM AUTHOR]

Au(~1 wt%)/TiO2(anatase or rutile or P25) nanocomposites were prepared by the solvated metal atom dispersion (SMAD) method, and the as-prepared samples were characterized by diffuse reflectance UV-visible spectroscopy, powder XRD, BET surface analysis measurements, and transmission electron microscopy bright field imaging. The particle size of the embedded Au nanoparticles ranged from 1 to 10 nm. These Au/TiO2 nanocomposites were used for photocatalytic hydrogen production in the presence of a sacrificial electron donor like ethanol or methanol under UV-visible and visible light illumination. These nanocomposites showed very good photocatalytic activity toward hydrogen production under UV-visible conditions, whereas under visible light illumination, therewas considerably less hydrogen produced.Au/P25 gave a hydrogen evolution rate of 1600 mol/h in the presence of ethanol (5 volume %) under UV-visible illumination. In the case of Au/TiO2 prepared by the SMADmethod, the presence of Au nanoparticles serves two purposes: as an electron sink gathering electrons fromthe conduction band (CB) of TiO2 and as a reactive site for water/ethanol reduction to generate hydrogen gas. We also observed hydrogen production by water splitting in the absence of a sacrificial electron donor using Au/TiO2 nanocomposites under UV-visible illumination. [ABSTRACT FROM AUTHOR]

In this study, nitrogen-doped mesoporous titania was synthesized by templating method using chitosan. This biopolymer chitosan plays the dual role of acting as a template (which imparts mesoporosity) and precursor for nitrogen. BET-SA, XRD, UV-DRS, SEM, and FTIR were used to characterize the photocatalyst. The doping of nitrogen into TiO2 lattice and its state was substantiated and measured by XPS. The photocatalytic activity of the prepared N-doped mesoporous titania for phenol and o-chlorophenol degradation was investigated under solar and artificial radiation. The rate of photocatalytic degradation was observed to be higher for o-chlorophenol than that of phenol. The photodegradation of o-chlorophenol was 98.62% and 72.2%, while in case of phenol, degradation to the tune of 69.25% and 30.58% was achieved in solar and artificial radiation. The effect of various operating parameters, namely, catalyst loading, pH, initial concentration and the effect of coexisting ions on the rate of photocatalytic degradation were studied in detail. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen, considered as the fuel for future can be produced from non-conventional, renewable and plentiful source like water. Novel zeolite-based materials that show photocatalytic properties in the visible light have been synthesized by incorporating titanium dioxide (TiO2), heteropolyacid (HPA) and transition metals like cobalt (Co). These materials show high efficiency for water splitting under visible light irradiation. Hydrogen (H2) generation to the tune of 2730μmol/h/g TiO2 has been obtained for the composite photocatalyst synthesized. Platinum (Pt) doping has also been attempted in this composite photocatalyst, however, no substantial enhancement in hydrogen generation was observed. The high efficiency of the composite photocatalyst suggests that the TiO2 which gets effectively dispersed and stabilized on the surface of zeolite works synergistically with transition metal like cobalt and heteropolyacid to make the material active in visible light for photoreduction of water to hydrogen. The aluminosilicate framework of zeolite also contributes towards delayed charge separation. This composite photocatalyst shows improvement in hydrogen evolution rate over other TiO2 based visibly active photocatalyst reported. [Copyright &y& Elsevier]

UV and visibly active photocatalytic materials based on zeolites have been designed, wherein, a hybrid photocatalytic material comprising charge transfer complex namely, heteropolyacid, a semiconductor and transition metal have been incorporated in the zeolite matrix to facilitate its usage for photoreduction of water to hydrogen. The photocatalytic materials synthesized using zeolite, TiO2 and heteropolyacid (HPA) are active in the UV range and the hydrogen yield works out to be of TiO2 catalyst in UV range, which is quite low as compared to that reported in literature. The photocatalytic materials developed by incorporation of HPA, TiO2 and are visibly active and are performing well as compared to reported materials in terms of their photoreduction properties and show potential for water splitting reaction in visible light. The maximum hydrogen yield works out to be of TiO2 in visible range which is substantially high as compared to other reported values for supported TiO2 based photocatalytic materials. [Copyright &y& Elsevier]