Solvothermal liquefaction of Tetra Pak waste into biofuels and Al2O3-carbon nanocomposite.

This study explores a novel solvothermal disposal technique of Tetra Pak waste for the co-synthesis of value-added bio-oil and alumina-carbon nanocomposite. The impact of residence time (10-50 min.), temperature (240-360 °C), and substrate-to-solvent ratio (1:4-1:10) on the solvothermal liquefaction of Tetra Pak waste with supercritical ethanol were investigated on a batch scale. Initially rise in operating temperature and residence time positively influenced the bio-oil yield. However, a decline in yield was seen beyond a certain point. A higher substrate-to-solvent ratio enhanced the bio-oil yield as the solvent demonstrated its effective capabilities to depolymerize the feedstock. The favorable condition for the highest bio-oil yield (34.41 %) and HHV (30.51 MJ/Kg) were found to be at 320 °C, 30 min, and a substrate-to-solvent ratio of 1:10. The synergetic effect of solvent (ethanol) and aluminium present in Tetra Pak leads to the formation of in-situ generated active hydrogen that enhances the bio-oil yields and inhibits residue formation. XRD and XPS analysis confirms the transformation of aluminium from (Al (0)) to (Al (+3)) in the presence of ethanol forming in-situ generated alumina-carbon nanocomposite that has the potential to be used as a catalyst. NMR, GC-MS, and FTIR analysis confirmed the richness of bio-oil in various organic compounds including alcohol, esters, ketones, ethers, acids, and phenols. The recovered ethanol from the process exhibits a significant potential to be reused as a solvent or as a fuel additive.

Hydrothermal flames for subaquatic, terrestrial and extraterrestrial applications.

Hydrothermal flames are formed in supercritical water in the presence of a fuel and an oxidant (usually air or oxygen). Integrating hydrothermal flames as the heat source for supercritical water oxidation helps to minimize the reaction time (to milliseconds), improve the reaction kinetics and reduce the chances of corrosion and reactor plugging. This review outlines state-of-the-art research on hydrothermal flames including the impacts of process parameters on flame ignition. The ignition and sustainability of hydrothermal flames are dependent on several factors such as the type of fuel and its concentration, type of oxidant (air and oxygen) as well as the temperatures and flow rate of the feed and oxidant. The article describes some novel applications of hydrothermal flames for clean energy production, geothermal energy recovery, deep well spallation, wastewater treatment, degradation of recalcitrant nitrogen-containing compounds and heavy oil upgrading. Finally, the challenges and future perspectives of hydrothermal flame applications are discussed. This review also highlights some technical considerations relating to hydrothermal flames such as the choice of organic solvent and its characteristics, preheating, ignition mechanism, flame stability and propagation, advanced reactor configurations, mixing with subcritical and supercritical components, recirculation zones, cooling mechanisms, corrosion and salt precipitation.

Catalytic and non-catalytic degradation of acetaminophen in supercritical water.

Pharmaceutical industrial wastewater is typical wastewater consisting of complex organic compounds with higher concentration, microbial toxicity, strenuous to deteriorate, and environmental threatening. The present work assesses the degradation of recalcitrant acetaminophen (ACM) by a green technology known as supercritical water oxidation (SCWO). Experiments were carried out in a continuous flow SCWO reactor by altering reaction conditions such as temperature 400-600 °C, oxidant coefficient (OC 0 to 3), and Fe(II) catalyst concentration (0.5 and 1 mg L-1) to study the technical feasibility of highly concentrated ACM. Liquid product analysis indicated the total organic carbon (TOC) removal efficiency could reach up to 99.5% without catalyst at 600 °C and 99.9% with Fe(II) at 500 °C. The addition of Fe not only suppressed the intermediate ring components but also promoted the formation of permanent gases via decarboxylation and reforming reactions. The reaction between Fe(II) and H2O2 in supercritical water is extremely fast, which has a direct impact on the system's operating conditions. The high activity exhibited by Fe(II) catalyst degraded the ACM completely at an operating condition of 500 °C. Maximum H2 fraction was attained without catalyst at 600 °C, OC 0.5, and with the catalyst at 500 °C, respectively, whereas, CO2 tends to rise significantly with both temperature and oxidant concentration. The catalytic process is efficient in comparison to the non-catalytic process. A possible reaction pathway was proposed based on the intermediates generated during the degradation.

Hydrothermal treatment of metal impregnated biomass for the generation of H2 and nanometal carbon hybrids.

The nanocatalyst impregnation onto the biomass matrix has gained importance in enhancing the H2 yield and overcoming the catalyst deactivation problems. In-situ catalytic gasification of Ru/Fe-impregnated sugarcane bagasse and citrus limetta (mosambi peels) were examined and compared with their raw biomass at subcritical and supercritical water conditions. Bagasse having a higher amount of lignocellulosic content produces a maximum yield of H2 over moambi peels. Besides, Ru and Fe nano-metal carbon hybrids with crystalline sizes between 10 and 25 nm were formed during in-situ hydrothermal gasification. The performance of hydrothermal gasification based on hydrogen yield was studied, and it relatively follows the order as temperature, nanoparticle composed, metal loading onto biomass matrix, type of catalyst, and biomass used. At the maximum operating temperature of 600 °C, B: W ratio 1:10 for the resident time of 60 min, highest H2 yield of 12.75 ± 0.17 and 11.20 ± 0.13 mmol/g attained for Ru and Fe impregnated bagasse with the CGE of 72.28 ± 2.17% and 67.08 ± 1.97% respectively. At similar operating conditions, H2 yields of 8.75 ± 0.18 and 8.13 ± 0.16 mmol/g were achieved with the CGE of 62.4 ± 1.91% and 53.7 ± 1.66% for Ru and Fe impregnated mosambi peels, respectively. Based on the H2 and CH4 production, Ru shows the highest performance than Fe catalyst.

Hydrothermal liquefaction of Fe-impregnated water hyacinth for generation of liquid bio-fuels and nano Fe carbon hybrids.

In this work, hydrothermal liquefaction experiments of iron impregnated water hyacinth were performed with a motive to enhance bio-oil yields along with generation of nanometal carbon hybrids. Iron nanoparticles were impregnated and its metal loading was determined by ICP-MS. The impact of operating parameters like temperature, biomass to water ratio and reaction time on bio-oil yields was studied. During hydrothermal liquefaction a maximum total bio-oil yield of 38.1% was obtained at 280 °C along with formation of nanometal carbon hybrids. The light oil and heavy oil fractions were characterized by GCMS and NMR for determining the key components. The light oil mainly comprises of alkanes, alcohols and esters whereas heavy oil contains esters, ethers, carboxylic acids and phenols. XRD and XPS of Fe-impregnated water hyacinth and residues confirmed the transition of Fe+3/+2 to Fe0. TEM analysis resulted an average particle size of Fe nanoparticles around 19.6 nm.

Green synthesis of nanometal impregnated biomass - antiviral potential.

Due to the epidemic nature, Chikungunya virus (CHIKV), arthropod-borne alphaviruses, is considered as a potential public health threat worldwide. Currently, no antiviral drug or vaccine is available against alphaviruses. Nanotechnology with green synthesis of nanoparticles is a novel and emerging interdisciplinary field of science that involves the production and usage of nanomaterials. Nano-biomaterials are clean, safe, non-toxic, cost effective and environment friendly which have been largely exploited to develop novel antiviral drugs in recent years. In the current work, different nanometals (Ag, Fe and Zn) were impregnated into raw Citrus limetta peels. The characterization of synthesized biomaterials was done using XRD and XPS which confirmed the presence of metallic forms of Fe and Ag whereas ZnO was formed during the impregnation process. Based on TEM analysis, the average size of nanoparticles was found to be 5, 32 and 12 nm for Ag, Fe and ZnO respectively. For evaluation of antiviral activity, nano-biomaterials AgNps, FeNps and ZnONps were processed for cell culture based experiments. All the three nano-biomaterials significantly reduced CHIKV viral titer and viral RNA level as determined by plaque assay, real time PCR and immunofluorescence assay. The results revealed that silver and iron nano-biomaterials have higher antiviral potential in comparison to zinc against CHIKV. In conclusion, green synthesized nano-biomaterials can act as good antiviral agents. These nano-biomaterials can further be processed for formulation of effective and promising nanomedicines against CHIKV and other similar viruses which are a threat to human health.

Thermogravimetric and kinetic studies of metal (Ru/Fe) impregnated banana pseudo-stem (Musa acuminate).

Pyrolysis/gasification have proved to be promising conversion techniques to convert biomass into fuels. The current research work focuses on impregnation of Ru and Fe into banana pseudo-stem to study kinetics, pyrolytic behaviour and their impact during pyrolysis through thermogravimetric analyser (TGA). Samples weight loss were analyzed by TGA at four different heating rates (5-20 °C min-1) over the temperature range of 30-900 °C. Isoconversional models such as Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sinose (KAS), and Kissinger's methods were employed to calculate the activation energy and pre-exponential factor for Ru-impregnated (FWO: Eα = 73.32 kJ mol-1, KAS: Eα = 68.23 kJ mol-1 and Kissinger's: Eα = 165.94 kJ mol-1) Fe-impregnated biomass (FWO: Eα = 86.78 kJ mol-1, KAS: Eα = 82.34 kJ mol-1 and Kissinger's: Eα = 192.37 kJ mol-1) and compared with raw biomass (FWO: Eα = 116.22 kJ mol-1, KAS: Eα = 113.39 kJ mol-1 and Kissinger's: Eα = 194.86 kJ mol-1). Lower activation energy and reduced weight loss were observed for metal impregnated biomass over the raw biomass.

A novel nano zero-valent iron biomaterial for chromium (Cr6+ to Cr3+) reduction.

This research work aims to develop a biomaterial entrapped with iron nanoparticles by green synthesis method in which biomass act as both reducing and capping agent. Iron nanoparticles embedded in Citrus limetta peels were characterised using ICP-MS for determination of metal loading, XRD, XPS for crystallinity and oxidation states, TEM followed by FESEM-EDS for particle size and morphology. Sizes of nanoparticles were found to be in the range of 4-70 nm. Batch experiments were conducted to study the effect of different parameters such as contact time, amount of biomaterial and volume of chromium(VI) solution for 2500 mg L-1 of Cr(VI). Complete reduction was attained for a contact time of 5 min with 1.5 g of biomaterial for initial concentration of 2500 mg L-1. The experimental results inferred that 1 g of biomaterial completely reduced 33 mg of hexavalent Cr to trivalent Cr. XRD and XPS revealed that iron nanoparticles are in amorphous form while XPS confirms Fe0 state. The transition of Fe0 to Fe2+/Fe3+ during the treatment with chromium solution confirms the reduction of Cr6+ to Cr3+.