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•PCBs were thermally treated to obtain metal rich pyrolysis residue (PPCBs).•PPCBs were roasted with NH4Cl for conversion of metals into metal chlorides.•Water was used as leaching ...solvent for recovery of metals from roasted residue.•93% of Cu, 100% of Ni, 100% of Zn and 100% of Pb were recovered.
The substantial growth of electronic waste (e-waste) in recent years has become a serious threat to environment. However, there is an excellent opportunity to recover and reuse metals present in e-waste, which eventually leads to conservation of natural resources for future generation. A greener and sustainable approach for the recovery of metals from electronic waste is the need of the hour. In this study, thermal decomposition of printed circuit boards (PCBs) was carried out in presence of nitrogen for conversion of polymers into oil and combustible gases. The metal rich pyrolysis residue was roasted in presence of ammonia chloride as chlorinating agent to recover metals. The effect of roasting parameters on the metal recovery investigated in temperature range of 200 °C to 325 °C for 1 h to 5 h while the NH4Cl dosage varied from 1 g/g to 4 g/g. Under the optimized roasting conditions, around 93% Cu, 100% Ni, 100% Zn, and 100% Pb were recovered at temperature of 300 °C, time of 4 h and NH4Cl dose of 3 g/g. The present process provides an eco-friendly solution for the recovery of metals from e-waste, which are valuable and avoid pollution.
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•Integrated lignocellulosic biorefinery paves a path towards circular economy.•Higher value added production from lignocellulosic biomass has commercial value.•Circular economy closes ...the loop towards biorefinery processes with effective waste management.
Lignocellulosic biomass is an effective and sustainable alternative for petroleum-derived fuels and chemicals to produce biofuels and bio-based products. Despite the high availability, the degradation of biomass is a substantial challenge. Hence, it is necessary to integrate several unit processes such as biochemical, thermochemical, physical, and catalytic conversion to produce wide range of bio-based products. Integrating these processes enhances the yield, reduces the reaction time, and can be cost-effective. Process integration could significantly lead to various outcomes which guides towards the circular economy. This review addresses integration of several biorefinery processes for the production of multifaceted products. In addition, modern and sustainable biorefinery technologies are discussed to pave the path towards circular economy through the closed-loop approach.
CO
2
co-feeding syngas conversion to sustainable fuels and valuable chemicals is one of the promising strategies for partial CO
2
abatement. Surface modifications of Mg promoted CuZn based catalysts ...via one pot non-ionic surfactant assisted co-precipitation route is an effective approach to facilitate the efficient CO/CO
2
hydrogenation to methanol. Herein, the influence of different surfactant/(CuZnMg) molar ratios on physicochemical properties and in selective methanol promotion was systematically investigated. The mesostructured CuZnMg (I–III) catalysts with varied molar ratios (0–0.06) led to difference in specific surface area, crystallite size, interaction between the lattices and density of basic sites. For the optimized catalyst CuZnMg (III) (molar ratio = 0.06), the CuO crystallite size, specific surface area and basic sites density was 7.2 nm, 31.23 m
2
/g and 14.6 µmol/m
2
respectively. Furthermore, the CuZnMg (III) displayed the highest exposed well dispersed CuO species and having strong interaction between Cu and ZnO lattice, as confirmed by H
2
-TPR analysis. Hence, CuZnMg (III) exhibited highest total carbon conversion (33.6%) and maximum methanol selectivity (72.5%) under identical reaction conditions (40 bar, 240 °C, 2000 mL/gcat.h). The effect of process parameters on total carbon conversion and methanol selectivity of CuZnMg (III) catalyst was also evidenced. Interestingly, the methanol selectivity and basic sites density correlates linearly with surfactant molar ratios and both were improved by 30% and 16% respectively for CuZnMg (III) catalyst when compared with conventional catalyst, highlighting the potential of surfactant assisted catalyst (CuZnMg (III)) for CO/CO
2
hydrogenation reactions.
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•Valorisation of lignocellulosic biomass into various useful products.•Integrating biological funnelling pathway in the bio-refinery concept.•Production of biofuels from biomass paves ...a path towards less carbon foot print.•Effective pre-treatment of lignocellulosic biomass enhances product yield.•Higher value added production from lignocellulosic biomass has good commercial value.
Biofuel is the presently needed potential energy reservoir as an alternative to wearying fossil fuel-based technology. Second generation lignocellulose is considered to be the most abundant source of renewable feedstock among the biomaterials. Lignocellulose biomass (LCB) is the effective feed stock for bio-based chemicals for carbon neutrality, which paves critical prospect for significant sustainable and renewable development. This review discusses the types of biomass, characterization, and value-added products developed. Integrating the biological funnelling pathway in the bio-refinery concept and explaining the genetic modification of lignocellulosic biomass for enhanced yield is also discussed. The outlook on lowering the carbon footprint by discussing in detail the life cycle carbon balance, process development tools, supply chain description, and circular economy.
Polyethylene terephthalate (PET) is a non‐degradable single‐use plastic and a major component of plastic waste in landfills. Chemical recycling is one of the most widely adopted methods to transform ...post‐consumer PET into PET's building block chemicals. Non‐catalytic depolymerization of PET is very slow and requires high temperatures and/or pressures. Recent advancements in the field of material science and catalysis have delivered several innovative strategies to promote PET depolymerization under mild reaction conditions. Particularly, heterogeneous catalysts assisted depolymerization of post‐consumer PET to monomers and other value‐added chemicals is the most industrially compatible method. This review includes current progresses on the heterogeneously catalyzed chemical recycling of PET. It describes four key pathways for PET depolymerization including, glycolysis, pyrolysis, alcoholysis, and reductive depolymerization. The catalyst function, active sites and structure‐activity correlations are briefly outlined in each section. An outlook for future development is also presented.
PET Cats! Recent development of heterogeneous catalysts for chemical recycling of polyethylene terephthalate (PET) is reviewed. PET is commercially used to produce bottles, film, packaging materials and synthetic fibers. Its chemical recycling produces renewable products, mitigating climate and environmental challenges as an alternative to using petroleum.
Solid acid catalysts occupy a special class in heterogeneous catalysis for their efficiency in eco-friendly conversion of biomass into demanding chemicals. We synthesized porphyrin containing porous ...organic polymers (PorPOPs) using colloidal silica as a support. Post-modification with chlorosulfonic acid enabled sulfonic acid functionalization, and the resulting material (PorPOPS) showed excellent activity and durability for the conversion of fructose to 5-hydroxymethyl furfural (HMF) in green solvent water. PorPOPS composite was characterized by N
sorption, FTIR, TGA, CHNS, FESEM, TEM and XPS techniques, justifying the successful synthesis of organic networks and the grafting of sulfonic acid sites (5 wt%). Furthermore, a high surface area (260 m
/g) and the presence of distinct mesopores of ~15 nm were distinctly different from the porphyrin containing sulfonated porous organic polymer (FePOP-1S). Surprisingly the hybrid PorPOPS showed an excellent yield of HMF (85%) and high selectivity (>90%) in water as compared to microporous pristine-FePOP-1S (yield of HMF = 35%). This research demonstrates the requirement of organic modification on silica surfaces to tailor the activity and selectivity of the catalysts. We foresee that this research may inspire further applications of biomass conversion in water in future environmental research.
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•Life Cycle Assessment (LCA) of algal-fuel production routes based on experimental data.•Environmental impacts beyond global warming potential critically discussed.•Environmental ...impacts of Anaerobic digestion > Environmental impacts of Hydrothermal liquefaction.•Based on LCA outcomes, improvement strategies suggested, to attain sustainability.
Studies highlighting the actual roadblocks in sustainability of algal fuels require systemic analysis using real-time experimental inventories. In view of this, the authors performed Life Cycle Assessments (LCAs) for 3 previously developed algal biofilms-based conversion systems; 1) wastewater grown algae (WWA) processed via anaerobic digestion (AD), 2) WWA processed via hydrothermal liquefaction (HTL) and 3) synthetic media grown algae (SMA) processed via HTL. Their environmental impacts were compared for resources depletion, ecosystem damage, human health deterioration and climate change. Results showed that HTL of WWA had 41.1 % lesser impact compared to AD of the same biomass, because of the huge energy input, production of CO2 and huge volume of algal digestate. Due to the short reaction time in HTL (20 min), energy input and resources usage was minimal. Further, the HTL of WWA showed 98% lesser impact than HTL of SMA. HTL of SMA had larger impact on the human health (3.95Pt), compared to HTL of WWA (0.25Pt). The latter also showed positive impact on the eutrophication reduction due to the treatment of wastewater during algal cultivation. The global warming potential for biocrude production from WWA was 10 times lower than biomethane production from the same biomass and 21 times lower than the biocrude production from SMA. The results of the comparative LCAs proved that HTL of WWA is a sustainable route for valorizing the biomass. Based on the LCA outcomes, shortcomings of the respective algal technologies were identified, and improvement strategies were suggested.
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•(PZ + DEA + H2O) as alternative to benchmark MEA-based solvents.•Interaction in (PZ + DEA + H2O) is established by thermo-physical parameters.•Higher reaction rate constant of ...(PZ + DEA + H2O) with CO2 than (PZ + AMP + H2O).•Replacing DEA by small PZ into blend, CO2 kinetics was enhanced significantly.•CO2 capture by (PZ + DEA + H2O) requires less energy than (PZ + MEA + H2O).
Although activated alkanolamine based solvents had great potential for energy-efficient post-combustion CO2 capture, yet these suffers from disadvantageous due to high capital cost of the process. In this research we developed and discussed the overall reaction scheme between CO2 and activated solvents. We investigated the kinetics of CO2 into piperazine (PZ) activated aqueous diethanolamine (DEA) by wetted-wall column contactor at (298–323) K, (5–15) kPa and fixed 3.0 kmol∙m−3. Physicochemical properties of such systems were determined while detailed uncertainty analysis were conducted. In thermodynamics point of view, liquid–liquid interaction were explored and evaluated by related parameters. The kinetics rate parameters for such activated solvents were interpreted based on kinetic study affording to the pseudo-first-order reaction method. At various temperature, kov of (PZ + DEA + H2O) were considerably larger than reported (AMP + PZ + H2O) systems. The results of kinetics study demonstrated that rate of CO2 in solvents were enhanced substantially as compared to DEA due to the addition of low quantity (0–0.45 kmol∙m−3) PZ into solvents. Besides, physicochemical properties were measured in terms of different models with absolute average deviation (AAD) < 5 %. Ultimately, (PZ + DEA + H2O) may be considered as vital solvents in amine scrubbing due to lower energy requirement for CO2 capture compared to (PZ + MEA + H2O).
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•Xylitol production from non-detoxified agro-industrial residues using P. fermentans.•Optimum glucose to xylose ratio and feed composition improved Xylitol accumulation.•Xylitol titer ...of 86.6 g/L with yield of 0.75 g/g was achieved from SCB hydrolysate.•OP hydrolysate resulted in xylitol titers of 71.9 g/L with a yield of 0.74 g/g.
Hemicellulosic sugars, the overlooked fraction of lignocellulosic residues can serve as potential and cost-effective raw material that can be exploited for xylitol production. Xylitol is a top platform chemical with applications in food and pharmaceutical industries. Sugarcane bagasse (SCB) and olive pits (OP) are the major waste streams from sugar and olive oil industries, respectively. The current study evaluated the potential of Pichia fermentans for manufacturing of xylitol from SCB and OP hydrolysates through co-fermentation strategy. The highest xylitol accumulation was noticed with a glucose and xylose ratio of 1:10 followed by feeding with xylose alone. The fed-batch cultivation using pure xylose, SCB, and OP hydrolysates, resulted in xylitol accumulation of 102.5, 86.6 and 71.9 g/L with conversion yield of 0.78, 0.75 and 0.74 g/g, respectively. The non-pathogenic behaviour and ability to accumulate high xylitol levels from agro-industrial residues demonstrates the potential of P. fermentans as microbial cell factory.
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