Investigating the performance of liquid and gas phase photoreactors for dynamic H2 production over bimetallic TiO2 and Ni2P dispersed MAX Ti3AlC2 monolithic nanocomposite under UV and visible light

Monolithic TiO2 and Ni2P dispersed 2D Ti3AlC2 MAX nanocomposite synthesized by sol-gel method, was investigated for stimulating photocatalytic H2 production. The performance was tested in three types of photoreactors including visible light irradiated slurry, visible and UV light irradiated fixed-bed and monolith photoreactors in batch and continuous operation. Using TiO2/Ni2P/Ti3AlC2 highest H2 production was achieved, which was 1.13, 3.25 and 3.80 times higher compared to TiO2/Ti3AlC2, TiO2/Ni2P and TiO2 samples. Under visible irradiation, slurry photoreactor in continuous operation depicted the highest activity, which was 23.6 and 32.5 times increased than fixed bed and monolith photoreactor, respectively. Using monolith photoreactor operating under UV light, 136 times more H2 was produced compared to monolith photoreactor under visible-light and 1.73 times higher H2 production than slurry photoreactor under visible-light. This was evidently due to higher penetration power of UV irradiations inside the monolith channels. The light penetration was declined when monolith channel length was increased or visible light was employed. With increasing feed composition, H2 production was further increased due to efficient oxidation and reduction reactions. Fixed-bed and monolith photoreactors operating in batch mode under visible light revealed 301 and 20 times higher H2 production than fixed bed and monolith photoreactors under continuous operation. The highest photonic yield and space yield were achieved using slurry photoreactor, while under UV light illuminated monolith showed highest apparent photonic yield and space yield. The findings of this work would be helpful to maximize photocatalytic H2 generation performance using various reactors under visible and UV irradiations

Hydrogels Based on Starch from Various Natural Sources: Synthesis and Characterization

Hydrogels based on a graft copolymer of acrylic acid (AA) and acrylamide (AAm) on a backbone of starch, obtained from different natural sources, have been prepared and characterized for potential agricultural use, as soil moisture regulators and nutrient sources for plant nutrition. Five types of starch are used: corn, waxy corn, wheat, potato, and rice starch. Hydrogels are prepared by a solution polymerization method, in the presence of ammonium persulphate (PSA) as initiator and N,N'-methylene-bis-acrylamide (MBA) as a cross-linking agent. Thermal and physico-chemical properties, such as thermogravimetry analysis and differential scanning calorimetry data and swelling properties of hydrogels, are observed. The influences of the cross-linking agent on the swelling ratio (SR) and solubility of prepared hydrogels are studied and optimized. The highest SR observed in water corresponded to non-cross-linked hydrogels prepared with waxy corn starch (780 g water per g dry matter), and the SR of these hydrogels in ammonium sulfate and calcium nitrate solutions are 9.6 and 1.2 g per g dry matter, respectively. Higher thermal stability is observed with cross-linked starch-g-(AA-AAm) hydrogels. The non-cross-linked hydrogels have a higher SR, but also have significant solubility in water.Byly připraveny hydrogely na bázi roubovaného kopolymeru škrobu z různých přírodních zdrojů, kyseliny akrylové a akryl amidu. Připravené hydrogely byly charakterizovány pro agrochemické účely, jako regulátor vlhkosti nebo jako nosič živin pro výživu rostlin. Pro syntézu bylo použito pět různých škrobů: kukuřičný, voskový kukuřičný, pšeničný, bramborový a rýžový. Hydrogely byly polymerizovány v roztoku v přítomnosti persíranu amonného (iniciátor) a N,N'-methylen-bis-akrylamidu (síťovací činidlo). U hydrogelů byly stanoveny tepelné a fyzikálně-chemické vlastnosti za použití termogravimetrické analýzy a diferenciální skenovací kalorimetrie. Dále byl studován a optimalizován vlivy síťovacího činidla na bobtnací poměr (SR) a rozpustnost připravených hydrogelů. Nejvyšší SR byl stanoven ve vodě u nezesítěného hydrogelu připraveného s voskovým kukuřičným škrobem (780 g vody na g sušiny) a SR tohoto hydrogelu v roztocích síranu amonného byl 9,6 g na g sušiny a dusičnanu vápenatého byl 1,2 g na g sušiny. Vyšší tepelná stabilita je pozorována u zesítěných hydrogelů a naopak nezesíťované hydrogely měly sice vyšší SR, ale také větší rozpustnost ve vodě