Search Results (11)

Carbonyl sulfide (COS), an organosulfur compound commonly present in industrial gases, poses significant challenges for environmental protection and industrial processes due to its toxicity. This paper reviews recent advancements in the development of catalysts for COS hydrolysis, emphasizing the effects of various supports and active components on catalyst performance, as well as the mechanisms underlying the hydrolysis reaction. Traditional supports like γ-Al₂O₃ demonstrate high activity for COS hydrolysis but are susceptible to deactivation. In contrast, novel supports such as activated carbon, TiO₂, and ZrO₂ have garnered attention for their unique structures and properties. The incorporation of active components, including alkali metals, alkaline earth metals, transition metals, and rare earth metals, significantly enhances the hydrolysis efficiency and resistance to deactivation of the catalysts. Additionally, this paper outlines three primary mechanisms for COS hydrolysis: the alkali-catalyzed mechanism, the Langmuir–Hinshelwood model, and the Eley–Rideal model mechanism, as well as the thiocarbonate intermediate mechanism, which collectively elucidate the conversion of COS into the H₂S and CO₂ catalyzed by these systems. Future research efforts will concentrate on developing high-activity, high-stability, and cost-effective COS hydrolysis catalysts, along with a more in-depth exploration of the reaction mechanisms to facilitate the efficient removal of COS from industrial emissions. Full article

Tandem alkali-catalyzed hydrolysis and alkaline electrolysis have gradually become appealing avenues for the reformation of polyester plastics into high-value-added chemicals and green hydrogen with remarkable environmental and economic benefits. In this study, an electrochemical upcycling strategy was developed for the electrocatalytic oxidation of polylactic acid (PLA) hydrolysate into valued C₂ chemicals (i.e., acetate) and hydrogen fuel using N, P-doped CuO_x nanowires (NW) supported on nickel foam (NF) as the electrocatalyst. This 3D well-integrated catalyst was easily prepared from a Cu(OH)₂ NW/NF precursor with Saccharomycetes as a green and safe P and N source. The electrocatalyst can efficiently catalyze the lactate monomer derived from the hydrolysis of PLA waste to acetate with high selectivity and exhibits a lower onset potential for the lactate oxidation reaction (LOR) than for water oxidation, saving 224 mV to deliver a current density of 30 mA/cm². The experimental results reveal that the plausible pathway of the LOR on these CuO_x NW involves oxidation and subsequent decarboxylation. Divalent copper species have been verified to be active sites for LOR via in situ Raman spectroscopy. Full article

In recent years, nanocellulosic materials have attracted special attention because of their performance in different advanced applications, biodegradability, availability, and biocompatibility. Nanocellulosic materials can assume three distinct morphologies, including cellulose nanocrystals (CNC), cellulose nanofibers (CNF), and bacterial cellulose (BC). This review consists of two main parts related to obtaining and applying nanocelluloses in advanced materials. In the first part, the mechanical, chemical, and enzymatic treatments necessary for the production of nanocelluloses are discussed. Among chemical pretreatments, the most common approaches are described, such as acid- and alkali-catalyzed organosolvation, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, ammonium persulfate (APS) and sodium persulfate (SPS) oxidative treatments, ozone, extraction with ionic liquids, and acid hydrolysis. As for mechanical/physical treatments, methods reviewed include refining, high-pressure homogenization, microfluidization, grinding, cryogenic crushing, steam blasting, ultrasound, extrusion, aqueous counter collision, and electrospinning. The application of nanocellulose focused, in particular, on triboelectric nanogenerators (TENGs) with CNC, CNF, and BC. With the development of TENGs, an unparalleled revolution is expected; there will be self-powered sensors, wearable and implantable electronic components, and a series of other innovative applications. In the future new era of TENGs, nanocellulose will certainly be a promising material in their constitution. Full article

The properties of biodiesel are completely dependent on the fatty acid profile of feedstock oils. Several feedstocks are not in use for biodiesel production because of the presence of unsuitable fatty acids in their oils. The present study was conducted to overcome this problem by the utilization of interesterification and hydrolysis processes. The present study reports biodiesel with much better cold flow properties than previous studies. Fatty acids present in Pongamia pinnata oil were optimized via interesterification and hydrolysis treatment of feedstock prior to alkali-catalyzed transesterification. The physiochemical properties of fuel were evaluated by standard test methods and the results were compared with EN 14214 and ASTM D6751 standards. Biodiesel composition was analyzed by a gas chromatographic analysis. The density, saponification and iodine values of the biodiesel derived from treated and non-treated oil were found to be within the range recommended by the international fuel standards. The acid values of biodiesel produced from non-treated and treated fractions were high (0.7–0.8 mg of KOH/g of oil), as compared to the biodiesel produced from non-treated and treated pure oil. The cloud points and pour points of biodiesel produced from hydrolyzed and interesterified oil were in the range of (8.1 to −9.6 °C) and (2.03 to −12.5 °C), respectively, while those of non-treated oil were in the range of (13.37 to −1.53 °C). These results indicate that treatments of oil specifically improved the low-temperature properties of biodiesel. Full article

Haloalkane dehalogenase (DhaA) catalyzes the hydrolysis of halogenated compounds through the cleavage of carbon halogen bonds. However, the low activity, poor environmental stability, and difficult recycling of free DhaA greatly increases the economic cost of practical application. Inspired by the organic–inorganic hybrid system, an iron-based hybrid nanocomposite biocatalyst FeHN@DhaA is successfully constructed to enhance its environmental tolerability. A series of characterization methods demonstrate that the synthesized enzyme–metal iron complexes exhibit granular nanostructures with good crystallinity. Under optimized conditions, the activity recovery and the effective encapsulation yield of FeHN@DhaA are 138.54% and 87.21%, respectively. Moreover, it not only exhibits excellent immobilized enzymatic properties but also reveals better tolerance to extreme acid, and is alkali compared with the free DhaA. In addition, the immobilized enzyme FeHN@DhaA can be easily recovered and has a satisfactory reusability, retaining 57.8% of relative activity after five reaction cycles. The results of this study might present an alternative immobilized DhaA-based clean biotechnology for the decontamination of organochlorine pollutants. Full article

Feruloyl esterase (FAE; EC 3.1.1.73) catalyzes the hydrolysis of the 4-hydroxy-3-methoxycinnamoyl group in an esterified sugar to assist in waste biomass degradation or to release ferulic acid (FA). An FAE-producing strain was isolated from humus soil samples and identified as Bacillus pumilus SK52.001. The BpFAE gene from B. pumilus SK52.001 was speculated and heterogeneously expressed in Bacillus subtilis WB800 for the first time. The enzyme exists as a monomer with 303 amino acids and a molecular mass of 33.6 kDa. Its specific activity was 377.9 ± 10.3 U/(mg protein), using methyl ferulate as a substrate. It displays an optimal alkaline pH of 9.0, an optimal temperature of 50 °C, and half-lives of 1434, 327, 235, and 68 min at 50, 55, 60, and 65 °C, respectively. Moreover, the purified BpFAE released 4.98% FA of the alkali-acidic extractable FA from de-starched wheat bran (DSWB). When the DSWB was enzymatically degraded by the synergistic effect of the BpFAE and commercial xylanase, the FA amount reached 49.47%. It suggested that the alkaline BpFAE from B. pumilus SK52.001, which was heterologously expressed in B. subtilis WB800, possesses great potential for biomass degradation and achieving high-added value FA production from food by-products. Full article

Greenhouse cultivation and harvesting generate considerable amounts of organic waste, including vegetal waste from plants and discarded products. This study evaluated the residues derived from tomato cultivation practices in Almería (Spain) as sugar-rich raw materials for biorefineries. First, lignocellulose-based residues were subjected to an alkali-catalyzed extrusion process in a twin-screw extruder (100 °C and 6–12% (w/w) NaOH) to assess maximum sugar recovery during the subsequent enzymatic hydrolysis step. A high saccharification yield was reached when using an alkali concentration of 12% (w/w), releasing up to 81% of the initial glucan. Second, the discarded tomato residue was crushed and centrifuged to collect both the juice and the pulp fractions. The juice contained 39.4 g of sugars per 100 g of dry culled tomato, while the pulp yielded an extra 9.1 g of sugars per 100 g of dry culled tomato after an enzymatic hydrolysis process. The results presented herein show the potential of using horticulture waste as an attractive sugar source for biorefineries, including lignocellulose-based residues when effective fractionation processes, such as reactive extrusion technology, are available. Full article

Today one of the most interesting ways to produce biodiesel is based on the use of oleaginous microorganisms, which can accumulate microbial oil with a composition similar to vegetable oils. In this paper, we present a thermo-chemical numerical model of the yeast biodiesel production process, considering cardoon stalks as raw material. The simulation is performed subdividing the process into the following sections: steam explosion pre-treatment, enzymatic hydrolysis, lipid production, lipid extraction, and alkali-catalyzed transesterification. Numerical results show that 406.4 t of biodiesel can be produced starting from 10,000 t of lignocellulosic biomass. An economic analysis indicates a biodiesel production cost of 12.8 USD/kg, thus suggesting the need to increase the capacity plant and the lipid yield to make the project economically attractive. In this regard, a sensitivity analysis is also performed considering an ideal lipid yield of 22% and 100,000 t of lignocellulosic biomass. The biodiesel production costs related to these new scenarios are 7.88 and 5.91 USD/kg, respectively. The large capacity plant combined with a great lipid yield in the fermentation stage shows a biodiesel production cost of 3.63 USD/kg making the product competitive on the current market of biofuels by microbial oil. Full article

Residues of Cistus ladanifer obtained after commercial steam distillation for essential oil production were evaluated to produce cellulose enriched solids and added-value lignin-derived compounds. The delignification of extracted (CLRext) and extracted and hydrothermally pretreated biomass (CLRtreat) was studied using two organosolv processes, ethanol/water mixtures (EO), and alkali-catalyzed glycerol (AGO), and by an alkali (sodium hydroxide) process (ASP) under different reaction conditions. The phenolic composition of soluble lignin was determined by capillary zone electrophoresis and by Py-GC/MS, which was also used to establish the monomeric composition of both the delignified solids and isolated lignin. The enzymatic saccharification of the delignified solids was also evaluated. The ASP (4% NaOH, 2 h) lead to both the highest delignification and enzymatic saccharification (87% and 79%, respectively). A delignification of 76% and enzymatic hydrolysis yields of 72% were obtained for AGO (4% NaOH) while EO processes led to lower delignification (maximum lignin removal 29%). The residual lignin in the delignified solids were enriched in G- and H-units, with S-units being preferentially removed. The main phenolics present in the ASP and AGO liquors were vanillic acid and epicatechin, while gallic acid was the main phenolic in the EO liquors. The results showed that C. ladanifer residues can be a biomass source for the production of lignin-derivatives and glucan-rich solids to be further used in bioconversion processes. Full article

This research focused on the influence of post-treatment using alkali-catalyzed hydrolysis with a full-aromatic nanofiltration (NF) polyamide membrane and its application to the efficient removal of selected dyes. The post-treated membranes were characterized through Fourier transform infrared spectroscopy, goniometry, and zeta-potential analysis to analyze the treatment-induced changes in the intrinsic properties of the membrane. Furthermore, the changes in permeability induced by the post-treatment were evaluated via the measurement of water flux, NaCl rejection, and molecular weight cutoff (MWCO) under different pH conditions and post-treatment times. Major changes induced by the post-treatment in terms of physicochemical properties were the enhancement of permeability, hydrophilicity, and negative charge due to the hydrolysis of the membrane’s amide bonds. Four different dyes were selected as representative organic pollutants considering the MWCO of the post-treated membranes. Compared with the pristine NF membrane, membranes post-treated at pH 13.5 showed better water flux with similar rejection of the target dyes. On the basis of these results, the proposed post-treatment method for NF membranes can be applied to the removal of organic pollutants of various size. Full article

Firstly, this paper reviews two main methods for biochar synthesis, namely conventional pyrolysis and hydrothermal carbonization (HTC). The related processes are described, and the influences of biomass nature and reaction conditions, especially temperature, are discussed. Compared to pyrolysis, HTC has advantages for processing high-moisture biomass and producing spherical biochar particles. Secondly, typical features of biochar in comparison with other carbonaceous materials are summarized. They refer to the presence of inorganics, surface functional groups, and local crystalline structures made up of highly conjugated aromatic sheets. Thirdly, various strategies for biochar modification are illustrated. They include activation, surface functionalization, in situ heteroatom doping, and the formation of composites with other materials. An appropriate modification is necessary for biochar used as a catalyst. Fourthly, the applications of biochar-based catalysts in three important processes of biofuel production are reviewed. Sulfonated biochar shows good catalytic performance for biomass hydrolysis and biodiesel production. Biodiesel production can also be catalyzed by biochar-derived or -supported solid-alkali catalysts. Biochar alone and biochar-supported metals are potential catalysts for tar reduction during or after biomass gasification. Lastly, the merits of biochar-based catalysts are summarized. Biochar-based catalysts have great developmental prospects. Future work needs to focus on the study of mechanism and process design. Full article