Maximum Catalytic Efficiency Research Articles

Ultrasonic assisted green synthesis of CuO nanoparticles: a real catalytic and antimicrobial agent

ABSTRACT This study reported facile biosynthesis of CuO nanoparticles employing leaf extract of Prosopis glandulosa as a stabilising agent by modest ultrasonic assisted technique. The synthesised nanoparticles were characterised via greatly refined systems comprising UV-visible, FTIR, XRD, SEM EDX, Zeta sizer, and Zeta potential. These facilities triggered the study of optical, functionality, crystallinity, surface morphology, elemental composition, and surface potential of the synthesised nanoparticles. The SEM and FT-IR analysis confirmed the semi-spherical shapes and functionalities of the synthesised NPs respectively. The zeta size and zeta potential of CuO NPs were established to be 65 nm and −1.42 mV respectively. The resultant NPs were applied as an efficient antimicrobial and catalytic candidate for the successful degradation of Eriochrome Black T (EBT) dye. Various factors were optimised such as dose, time, and NaBH4 concentration to achieve maximum catalytic efficiency of CuO nanoparticles. The NPs show excellent catalytic performance of about 92% degradation of EBT within 30 minutes. The antimicrobial performance was also tested by varying the concentration of NPs (250, 500, 1000, and 2000 g/mL via disc diffusion protocol. The results show that CuO NPs have excellent antibacterial activity alongside E. coli at MIC values of 250 g/mL as equated to S. areas and Aspergillus niger.

Highly stable Ag-doped Cu2O immobilized cellulose-derived carbon beads with enhanced visible-light photocatalytic degradation of levofloxacin

Ag-doped Cu2O immobilized carbon beads (Ag/Cu2O@CB) based composite photocatalysts have been prepared for the removal of levofloxacin, an antibiotic, from water. The photocatalysts were prepared by the processes of chemical reduction and in-situ solid-phase precipitation. The composite photocatalyst was characterized by a porous and interconnected network structure. Ag nanoparticles were deposited on Cu2O particles to develop a metal-based semiconductor to increase the catalytic efficiency of the system and the separation efficiency of the photogenerated carriers. Cellulose-derived carbon beads (CBs) can also be used as electron storage libraries which can capture electrons released from the conduction band of Cu2O. The results revealed that the maximum catalytic degradation efficiency of the composite photocatalyst for the antibiotic levofloxacin was 99.02 %. The Langmuir–Hinshelwood model was used to study the reaction kinetics, and the process of photodegradation followed first-order kinetics. The maximum apparent rate was recorded to be 0.0906 min-1. The mass spectrometry technique showed that levofloxacin degraded into carbon dioxide and water in the presence of the photocatalyst. The results revealed that the easy-to-produce photocatalyst was stable and efficient in levofloxacin removing.

Sunlight driven photocatalytic degradation of organic pollutants by solvothermally synthesized rGO-BiVO4 nanohybrids

This study reports photocatalytic degradation of organic dyes by rGO-BiVO4 nanohybrids. rGO- BiVO4 nanohybrids were solvothermally prepared with different rGO loading (1.5, 3 and 6 %) and their structural, optical and photocatalytic properties were investigated. Effect of rGO loading on photocatalytic dye degradation was studied and the factors responsible were analyzed. Structural analysis was done using XRD and Raman analyses which clearly showed monoclinic phase of the BiVO4. FESEM images showed sub-micron spheres of BiVO4 along with sheet-like structures corresponding to rGO. A slight change in the band gap was observed from 2.2 eV for BiVO4 to around 2 eV for the rGO-BiVO4 nanohybrids. Band to band transitions as well as the transitions from the defect bands were observed from the PL spectra. Photocatalytic degradation studies of organic pollutant MB under natural sunlight showed 3 % rGO-BiVO4 to be the best photocatalyst which degraded 88.4 % of MB in 80 min with rate constant of 0.0244 min−1. It was observed that for obtaining a maximum catalytic efficiency an optimum loading of rGO proved to be best. In either case of higher or lower loading of rGO showed a lower degradation performance. Amongst the samples synthesized 3 % rGO loading was found to be the optimum rGO loading to have the lowest band gap (2 eV) as well as the reduced recombination that has resulted in highest photocatalytic efficiency under solar irradiation.

Modification of red mud catalyst using oxalic acid-assisted UV treatment for toluene removal

An innovative simplified modification method for red mud had been proposed, which enabled its utilization as an active Fe2O3-rich component for catalytic oxidation of toluene. The Box-Behnken design, based on Response Surface Methodology (RSM), was employed to optimize the modification of bauxite residue using oxalic acid combined with UV irradiation. Based on the experimental conditions, the optimal conditions for three independent parameters were determined: acid leaching time (2 hours), UV irradiation time (1 hour), and acid dosage (150 ml),which was in order to enhance the maximum catalytic efficiency of toluene at 300 °C. Under the optimal preparation conditions provided by the Box-Behnken design, the catalytic efficiency of toluene at 300°C could reach 99.2%. In comparison to the acid-modified mud (MRM) and untreated bauxite residue (RM), the aluminum refinery residue modified with oxalic acid-assisted UV irradiation (MRM-UV) exhibited the formation of oxalate sub-iron precipitates, resulting in significantly lower catalytic temperatures (238°C). Furthermore, through XRF, XRD, XPS, O2-TPD, and H2-TPD analysis, it was discovered that a large amount of iron oxide and calcium oxide formed CaO+Fe2O3→Ca2Fe2O5, strengthening the interaction between iron and calcium, augmenting the migration rate of lattice oxygen from the bulk phase to the surface. Consequently, T50 were reduced by 20.9% and 31.8% when compared to MRM and RM. Moreover, the CO2 selectivity of MRM-UV increased from 8.6% to 70.5% compared to RM at 300°C. Using in situ DRIFTS, the reaction pathway of toluene on MRM-UV was identified as benzyl alcohol → benzaldehyde or benzoyl → benzoate→maleic anhydride→CO2 and H2O. The process refinement reduced VOCs emissions and promoted sustainable waste management by combining oxalic acid with catalytically active red mud.

Unveiling the Broad Substrate Specificity of Deoxynivalenol Oxidation Enzyme DepA and Its Role in Detoxifying Trichothecene Mycotoxins.

DepA, a pyrroloquinoline quinone (PQQ)-dependent enzyme isolated from Devosia mutans 17-2-E-8, exhibits versatility in oxidizing deoxynivalenol (DON) and its derivatives. This study explored DepA's substrate specificity and enzyme kinetics, focusing on DON and 15-acetyl-DON. Besides efficiently oxidizing DON, DepA also transforms 15-acetyl-DON into 15-acetyl-3-keto-DON, as identified via LC-MS/MS and NMR analysis. The kinetic parameters, including the maximum reaction rate, turnover number, and catalytic efficiency, were thoroughly evaluated. DepA-PQQ complex docking was deployed to rationalize the substrate specificity of DepA. This study further delves into the reduced toxicity of the transformation products, as demonstrated via enzyme homology modeling and in silico docking analysis with yeast 80S ribosomes, indicating a potential decrease in toxicity due to lower binding affinity. Utilizing the response surface methodology and central composite rotational design, mathematical models were developed to elucidate the relationship between the enzyme and cofactor concentrations, guiding the future development of detoxification systems for liquid feeds and grain processing. This comprehensive analysis underscores DepA's potential for use in mycotoxin detoxification, offering insights for future applications.

Xylanase Production by Cellulomonas phragmiteti Using Lignocellulosic Waste Materials

Lignocellulosic biomass holds promise as a renewable feedstock for various applications, but its efficient conversion requires cost-effective degradation strategies. The main objective of this study was to investigate the effect of the growth conditions of Cellulomonas phragmiteti in the production of (hemi)cellulosic supernatants. To meet this aim, different lignocellulosic residues were used as carbon sources for growth using defined mineral or nutritive culture media. Cell-free culture supernatants with xylanolytic activity were produced in all the conditions evaluated, but the highest xylanase activity (15.3 U/mL) was achieved in Luria–Bertani (LB) medium containing 1% waste paper. Under these conditions, almost negligible β-glucosidase, cellobiohydrolase, β-xylosidase, and α-arabinofuranosidase activity was detected. The xylanolytic supernatant showed tolerance to salt and displayed maximal catalytic efficiency at pH 6 and 45 °C, along with good activity in the ranges of 45–55 °C and pH 5–8. As it showed good stability at 45 °C, the supernatant was employed for the hydrolysis of birchwood xylan (50 g/L) under optimal conditions, releasing 10.7 g/L xylose in 72 h. Thus, C. phragmiteti was found to produce a xylanolytic enzymatic supernatant efficiently by utilizing the cheap and abundant lignocellulosic residue of waste paper, and the produced supernatant has promising attributes for industrial applications.

Evaluation of arsenic pollution in field-contaminated soil at the soil's actual pH

The pollution and ecological risks posed by arsenic (As) entering the soil are the major environmental challenges faced by human beings. Soil phosphatase can serve as a useful indicator for assessing As contamination under specific soil pH conditions. However, the study of phosphatase kinetics in long-term field As-contaminated soil remains unclear, presenting a significant obstacle to the monitoring and evaluation of As pollution and toxicity. The purpose of this study was to determine phosphatase activity and explore enzyme kinetics in soils subjected to long-term field As contamination. Results revealed that the soil phosphatase activity varied among the tested soil samples, depending on the concentrations of As. The relationship between total As, As fractions and phosphatase activity was found to be significant through negative exponential function fitting. Kinetic parameters, including maximum reaction velocity (Vmax), Michaelis constant (Km) and catalytic efficiency (Vmax/Km), ranged from 3.14 × 10−2–53.88 × 10−2 mmol/(L·hr), 0.61–7.92 mmol/L, and 0.46 × 10−2–11.20 × 10−2 hr−1, respectively. Vmax and Vmax/Km of phosphatase decreased with increasing As pollution, while Km was less affected. Interestingly, Vmax/Km showed a significant negative correlation with all As fractions and total As. The ecological doses (ED10) for the complete inhibition and partial inhibition models ranged from 0.22–70.33 mg/kg and 0.001–55.27 mg/kg, respectively, indicating that Vmax/Km can be used as an index for assessing As pollution in field-contaminated soil. This study demonstrated that the phosphatase kinetics parameters in the soil's pH system were better indicators than the optimal pH for evaluating the field ecotoxicity of As.

Synthesis, Characterization, and Environmental Applications of Cu-Ni-Doped Bismuth Molybdate

Bismuthoxide-based catalysts gained attention for photocatalytic remediation of environmental pollutants owing to their low cost, feasibility, stability, small, and tunable band gap. In the present work, bismuth molybdate was modified via transition metal doping to achieve maximum catalytic efficiency. This aim was accomplished by synthesizing novel Cu2+ and Ni2+ codoped bismuth molybdate (CuNi/Bi2MoO6, Cu/Bi2MoO6, and Ni/Bi2MoO6) which were utilized for heavy metal reduction and dyes degradation. Pure bismuth molybdate was also fabricated for comparative studies. All the prepared samples were characterized by XRD, Raman spectroscopy, SEM, and EDX. Optical studies for band gap calculations were carried out by UV-Visible spectrophotometry and decrease in band gap was observed in doped materials. Pseudo-first-order kinetic studies were performed to find the rate constants and regression values for Cr(VI) reduction and degradation of rhodamine B and malachite green using CuNi/Bi2MoO6. Codoped bismuth molybdate exhibited more than 95% photocatalytic performance for Cr(VI) reduction and degradation of rhodamine B and malachite green dyes. Reusability of catalyst was confirmed up to six cycles. Considering its catalytic proficiency, CuNi/Bi2MoO6 is anticipated to be utilized for more environment friendly applications in future.

Impact of alternate Mn doping in ternary nanocomposites on their structural, optical and antimicrobial properties: Comparative analysis of photocatalytic degradation and antibacterial activity

The present study was done to investigate and compare the photocatalytic and antibacterial activity of two in situ Manganese doped ternary nanocomposites. The dual ternary hybrid systems comprised Mn-doped Ag2WO4 coupled with MoS2-GO and Mn-doped MoS2 coupled with Ag2WO4-GO. Both hierarchical alternate Mn-doped ternary heterojunctions formed efficient plasmonic catalysts for wastewater treatment. The novel nanocomposites were well-characterized using XRD, FTIR, SEM-EDS, HR-TEM, XPS, UV-VIS DRS, and PL techniques confirming the successful insertion of Mn+2 ions in respective host substrates. The bandgap of the ternary nanocomposites evaluated by the tauc plot showed them visible light-active nanocomposites. The photocatalytic ability of both Mn-doped coupled nanocomposites was investigated against the dye methylene blue. Both ternary nanocomposites showed excellent sunlight harvesting ability for dye degradation in 60 min. The maximum catalytic efficiency of both photocatalysts was obtained at a solution pH value of 8, photocatalyst dose and oxidant dose of 30 mg/100 mL and 1 mM for Mn–Ag2WO4/MoS2-GO, 50 mg/100 mL, 3 mM for Mn–MoS2/Ag2WO4-GO keeping IDC of 10 ppm for all photocatalysts. The nanocomposites showed excellent photocatalytic stability after five successive cycles. The response surface methodology was used as a statistical tool for the evaluation of the photocatalytic response of several interacting parameters for dye degradation by ternary composites. The antibacterial activity was determined by the inactivation of gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria by support-based doped ternary hybrids.

Selective incorporation of 5-hydroxytryptophan blocks long range electron transfer in oxalate decarboxylase.

Oxalate decarboxylase from Bacillus subtilis is a binuclear Mn-dependent acid stress response enzyme that converts the mono-anion of oxalic acid into formate and carbon dioxide in a redox neutral unimolecular disproportionation reaction. A π-stacked tryptophan dimer, W96 and W274, at the interface between two monomer subunits facilitates long-range electron transfer between the two Mn ions and plays an important role in the catalytic mechanism. Substitution of W96 with the unnatural amino acid 5-hydroxytryptophan leads to a persistent EPR signal which can be traced back to the neutral radical of 5-hydroxytryptophan with its hydroxyl proton removed. 5-Hydroxytryptophan acts as a hole sink preventing the formation of Mn(III) at the N-terminal active site and strongly suppresses enzymatic activity. The lower boundary of the standard reduction potential for the active site Mn(II)/Mn(III) couple can therefore be estimated as 740 mV against the normal hydrogen electrode at pH4, the pH of maximum catalytic efficiency. Our results support the catalytic importance of long-range electron transfer in oxalate decarboxylase while at the same time highlighting the utility of unnatural amino acid incorporation and specifically the use of 5-hydroxytryptophan as an energetic sink for hole hopping to probe electron transfer in redox proteins.

Green and efficient synthesis of highly liposoluble and antioxidant L-ascorbyl esters by immobilized lipases

L-ascorbyl palmitate (LAP) is the permitted antioxidant used in baby food, but its high commercial demand is suppressed by poor liposolubility. In this paper, a cleaner and more efficient method to synthesize the high-liposoluble and antioxidant unsaturated fatty acid ascorbyl esters (UFAAE) is proposed, based on the enzymatic catalysis using CaLB immobilized on the ordered mesoporous silicon (CaLB@OMS-C8). The results indicated that the maximum catalytic efficiency (CE) in CaLB@OMS-C8 could reach 20.8 M g−1 h−1, thus facilitating the high conversions of 71.8%, 74.1% and 76.8% for L-ascorbyl oleate (LAO), L-ascorbyl linoleate (LAL) and L-ascorbic acid linolenic ester (LALN), respectively. The higher yield of LALN was explained by molecular docking technology as lipase CaLB presented a high binding affinity to linolenic acid (−18.8 kJ/mol) than those to oleic acid (−9.2 kJ/mol) and linoleic acid (−15.4 kJ/mol). By using unsaturated fatty acids as acyl donors, the synthesized UFAAE exhibited a lower melting point, better liposolubility and comparable antioxidant ability compared to LAP. This method to synthesize the high-soluble and antioxidant L-ascorbyl esters by the enzymatic esterification between L-ascorbic acid and unsaturated fatty acids shows great potential as a clean and efficient approach for future industrial production.

Constructing Z-scheme g-C3N4/TiO2 heterostructure for promoting degradation of the hazardous dye pollutants

The use of dyes and segments has increased widely in recent years, but it poses a serious health risk to ecosystems. In this work, TiO2 and two-dimensional g-C3N4 nanosheets (g-CN) were fabricated through co-precipitation and thermal polymerization technique, respectively. The g–CN–TiO2 photocatalyst (1: 3, 2: 2, 3: 1) in various weight percentages was prepared using a simple impregnation process. The photocatalytic behaviour of the g-CN, TiO2 NPs, and different weight percentages of g–CN–TiO2 photocatalyst was evaluated against methylene blue (MB) dye under UV–visible light illumination. Compared to pristine and other weight percentages of the g–CN–TiO2 nanocomposite, the optimized g–CN–TiO2 nanocomposite (3:1) showed promoted performance against MB dye. The enriched catalytic efficiency can be accredited to the low amount of TiO2 nanoparticles deposited on gCN nanosheets, possibly due to the boosted transport properties of the electron-hole pairs. The enriched photocatalytic behaviour can be attributed to the development of the Z-scheme system between TiO2 and g-CN. The current study is an outstanding demonstration of the development of maximum catalytic efficiency for destroying hazardous chemical dyes.

DNA-directed coimmobilization of multiple enzymes on organic-inorganic hybrid DNA flowers.

The artificial multienzyme systems developed by mimicking nature has attracted much interest. However, precisely controlled compositions and ratios of multienzymatic co-immobilization systems are still limited by the indistinguishable nature of enzymes. Herein, a strategy for fabricating DNA-directed immobilization of horseradish peroxidase (HRP) and glucose oxidase (GOx) on hybrid DNA nanoflowers (GOx-HRP@hDFs) is presented. The preparation of micron-sized hybrid DNA flowers (hDFs) begins with the predetermined repeatable polymer-like DNA sequences which contained two strands. The hDFs structure is generated through one-pot rolling circle amplification (RCA) and self-assembly with magnesium pyrophosphate inorganic crystals. Based on the rigid-base pairing, GOx and HRP conjugated with sequences complementary to strands would be anchored to the predesigned locations, respectively. By adjusting the loading amount/ratio of enzymes properly, the maximal catalytic efficiency can be precisely regulated. The reaction activity of GOx-HRP@hDFs was 7.4 times higher than that of the free GOx-HRP under the optimal mole ratio (GOx/HRP 4:1). In addition, this multienzyme catalyst system exhibits excellent precision, specificity, reproducibility, and long-term storage stability when applied to real human blood samples. The preceding results validate that GOx-HRP@hDFs are promising candidates for personal diabetes detection.

Effects of nitrogen addition on the kinetic parameters of soil acid phosphomonoesterase in a Moso bamboo forest

Soil phosphatases are important in the mineralization of organophosphates and in the phosphorus (P) cycle. The kinetic mechanisms of phosphatases in response to nitrogen (N) deposition remain unclear. We carried out a field experiment with four different concentrations of N: 0 g N·hm-2·a-1(control), 20 g N·hm-2·a-1(low N), 40 g N·hm-2·a-1(medium N), and 80 g N·hm-2·a-1(high N) in a subtropical Moso bamboo forest. Soil samples were then collected from 0 to 15 cm depth, after 3, 5 and 7 years of N addition. We analyzed soil chemical properties and microbial biomass. Acid phosphatase (ACP) was investigated on the basis of maximum reaction velocity (Vm), Michaelis constant (Km), and catalytic efficiency (Ka). Results showed that N addition significantly decreased soil dissolved organic carbon (DOC), available phosphorus, and organophosphate content, but significantly increased soil ammonium, nitrate-N content, and Vm. There was a significant relationship between Vm and the concentrations of available phosphorus, organophosphate, and soil DOC. In general, N addition substantially increased Ka, but did not affect Km. The Km value in the high N treatment group was higher than that in the control group after five years of N addition. Km was significantly negatively associated with both available phosphorus and organophosphate. Medium and high N treatments had stronger effects on the kinetic parameters of ACP than low N treatment. Results of variation partition analysis showed that changes in soil chemical properties, rather than microbial biomass, dominated changes in Vm(47%) and Km(33%). In summary, N addition significantly affected substrate availability in Moso bamboo forest soil and modulated soil P cycle by regulating ACP kinetic parameters (especially Vm). The study would improve the understanding of the mechanisms underlying soil microorganisms-regulated soil P cycle under N enrichment. These mechanisms would identify the important parameters for improving soil P cycling models under global change scenarios.

Reusable and highly stable MoS[formula omitted] nanosheets for photocatalytic, sonocatalytic and thermocatalytic degradation of organic dyes: Comparative study

The presence of emerging pollutants in industrial wastewater is a global problem and requires appropriate treatment techniques. Herein, reusable, stable and highly efficient MoS2 nanosheets are prepared via a one-step hydrothermal process. The prepared MoS2 nanosheets are proposed as an environmentally friendly catalyst for treating polluted waters. The comparative effectiveness of the photocatalytic, sonocatalytic, and thermocatalytic degradation processes for the elimination of Rhodamine B (RhB) is investigated. The morphology, composition, and optical properties of the prepared MoS2 nanostructure are characterized using different tools. The vertically aligned MoS2 nanosheets are confirmed by TEM. Moreover, the D-spacing of the nanosheets and corresponding band gap are found to be 0.6 nm and 1.19 eV, respectively. The remarkable catalytic degradation performance of MoS2 nanosheets via the three advanced oxidation processes (AOPs) is attributable to its two-dimensional stacked layers. By using various active species traps, it is proven that the superoxide anion is the major reactive species in the photocatalytic and sonocatalytic degradation of RhB dye. In the case of the thermocatalytic process, holes have the main role. Maximum catalytic efficiency over MoS2 nanosheets is observed with removal percentages of 100 %, 100 % and 80 % after 15 min for photocatalytic, sonocatalytic, and thermocatalytic degradation, respectively. Moreover, the dye degradation and mineralization are confirmed by high COD removal. The MoS2 nanosheets showed high chemical stability after recycling. Consequently, these hydrothermally prepared MoS2 nanosheets can be considered as a promising catalyst for the degradation of emerging pollutants from an aqueous solution.

Experimental investigation on sucrose/alumina catalyst coated converter in gasoline engine exhaust gas.

In this study, a modified catalytic converter was employed to treat the harmful exhaust gas pollutants of a twin-cylinder, four-stroke spark-ignition engine. This research mainly focuses on the emission reduction of unburnt hydrocarbons, carbon monoxide, and nitrogen oxides at low light-off temperatures. A sucrolite catalyst (sucrolite) was coated over the metallic substrate present inside the catalytic converter, and exhaust gas was allowed to pass through it. A scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectroscopy were used to investigate the changes in morphology, chemical compounds, and functional group elements caused by the reactions. Catalytic reactions were studied by varying the engine loads and bed temperatures, and the results were compared with those of the commercial catalytic converter. The results show that sucrose present in the catalyst was suitable at low temperatures while alumina was suitable for a wide range of temperatures. In the case of the modified catalytic converter, the maximum catalytic conversion efficiencies achieved for oxidizing CO and HC were 70.73% and 85.14%, respectively, and for reduction reaction at NOx was 60.22% which is around 42% higher than in commercial catalytic converter. As a result, this study claims that sucrolite catalyst is effective for low-temperature exhaust gas.

EFFECT OF IMMOBILIZATION PROTOCOL ON CATALYTIC ACTIVITY OF CRL IMMOBILIZED ONTO OIL PALM LEAVE-SILICA-MAGNETITE SUPPORT

Purpose: The purpose of the study was to establish the optimal conditions required for the attachment of Candida rugosa lipase (CRL) onto silica extracted from ash of acid treated oil palm leaves, for maximum catalytic efficiency.
 Methodology: Six different concentrations of CRL solution ranging from 1 mg/mL to 6 mg/mL, immobilization time of 4, 8, 12, 16, 20 and 24 h as well as immobilization temperature of 4, 25, 30, 35 40 and 45 were independently investigated. In this study, the parameter to be investigated was varied while others were fixed. The effectiveness of the immobilization protocol were assessed using four catalytic parameters – protein loading, immobilization yield, specific activity and ester yield. Statistical analysis was performed using one way ANOVA (IBM SPSS -20.0) software while significant differences within ranges in a parameter, if any was given as p 0.05.
 Findings: The study revealed that the optimal values of concentration of CRL solution, immobilization time and immobilization temperature required to immobilize CRL onto SiO2-MNPs derived from oil palm leave were 5. 0 mg/mL, 16 h and 25 respectively. At this optimal conditions, protein loading (33.3, 38.1, 20.5 mg/g), immobilization yield (57.8, 70.0, 59.0 %), specific activity (74.6, 63.5, 72.2 U/g) and ester yield (85.0, 74.1, 85.5 %) respectively were achieved.
 Recommendation: Optimization of the immobilization protocol for immobilizing CRL onto silica support extracted from the highly abundant oil palm leave – an agricultural biomass, will not just produce a biocatalyst of with high catalytic efficiency but would circumvent the environmental pollution arising from dumping of large quantities of the biomass into the ecosystem. It is recommended from the findings of this study that 5.0 mg/mL CRL solution be immobilized onto glutaraldehyde activated SiO2-MNPs support matrix derived from oil palm leave for 16 h at 25.

Immobilization of Thermomyces lanuginosus lipase via ionic adsorption on superparamagnetic iron oxide nanoparticles: Facile synthesis and improved catalytic performance

The present work describes a simple, rational, and optimized methodology for the immobilization of lipase from Thermomyces lanuginosus (TLL) via ionic adsorption on non-commercial superparamagnetic iron oxide nanoparticles (SPIONs). First, the surface loads of both the enzyme and nanoparticles were evaluated by zeta potential measurements over a wide pH range. In addition, the loading surface of TLL was mapped computationally using the information obtained from the Protein Data Bank (PDB) under three different pH conditions. This information allowed to conduct the directional immobilization of the lipase on the surface of the SPIONs in order to maximize the lipase–SPION interaction and keep the enzyme’s active sites facing the solution. TLL was immobilized at a low ionic strength (5 mmol L–1) on the SPIONs under optimized conditions (sodium acetate buffer, pH 4, 25 °C using an initial enzyme loading of 30 mg per gram of support). Under such conditions, almost full immobilization (99.49% adsorption capacity) was observed. The prepared biocatalyst retained 62.3% of its hydrolytic activity relative to the initial activity of the free lipase. Maximum catalytic efficiency (or acid conversion percentage) of 80% in decyl oleate synthesis performed in a solvent-free system was observed after 12 consecutive cycles of reaction of 180 min each. In addition, the lipase–nanoparticle interaction was also evaluated by fluorescence spectroscopy and the thermodynamic parameter values ΔGo=-25.8kJmol-1, ΔHo=-10.44kJmol-1, and, ΔSo=0.122kJmol-1K-1 were found, which is consistent with the occurrence of predominantly ionic interactions. These results clearly show the promising use of the prepared biocatalyst to catalyze decyl oleate production, an ester with emollient properties, in an eco-friendly process (solvent-free system).

Noticeably Improved Visible Light Photocatalytic Activity of TiO2 Nanoparticles through co‐Doping of Activated Charcoal and Fe Towards Methylene Blue Degradation

AbstractGenerating enormous oxygen radicals with metal oxides is a viable route to achieve efficient and eco‐friendly photocatalysis. To this aim, we co‐doped the TiO2 nanoparticles with activated charcoal (AC) and Fe (transition element) for the methylene blue (MB) dye degradation. The AC significantly enhances the adsorption of MB on the TiO2 surface, whereas the Fe dopants decrease its bandgap. To begin with, the modified TiO2 is prepared with chemical methods and the structural and morphological recordings are performed with XRD and FESEM, respectively. Then the elemental compositions and their oxidation states are probed with XPS analysis. The efficient charge carrier separation under white light illumination enhances the photocatalytic activity of modified TiO2 than its counterpart. The photocatalytic studies show that, 56 and 74 % of methylene blue dye degradation occurs with Fe doped TiO2 and AC doped TiO2 respectively. Interestingly, a maximum catalytic efficiency of 98 % is obtained for the Fe, AC co‐doped TiO2 samples in 90 min, and we provide a novel strategy to convert the large bandgap TiO2 into visible light photocatalyst.

NOx Emissions below the Prospective EURO VII Limit on a Retrofitted Heavy-Duty Vehicle

In this study, a EURO VI heavy-duty vehicle (HDV) has been retrofitted with an exhaust gas heater (EGH) with the objective to reduce its NOx emissions below the current EURO VI and EURO VII limits. Results show that an EGH of 5 kW is enough to produce a significant NOx emissions abatement below the EURO VI and EURO VII limits. A conventional after-treatment system heated using a 5 kW EGH could work at its maximum catalytic conversion efficiency of 95% regardless of the engine operating speed. Consequently, exhaust gas heaters are a potential solution to high NOx emission at low engine regimes. With the use of an EGH, urea can be injected sooner, and catalytic reactions could cut much more NOx emissions. However, its incorporation would increase the vehicle’s fuel consumption by 1.47% if it is connected directly to the vehicle’s electrical system. Finally, it is also demonstrated that an automotive thermoelectric generator (ATEG) can supply the energy required by the EGH through the conversion of the waste heat from exhaust gases into electricity. This system could work electrically autonomous so there is no extra consumption of fuel.