Optimum pH Value Research Articles

Enhancing photocatalytic degradation of beta-blocker drugs using TiO2 NPs/zeolite and ZnO NPs/zeolite as photocatalysts: optimization and kinetic investigations

This study delves into the development and optimization of photocatalysts, namely ZnO NPs/Zeolite and TiO2 NPs/Zeolite, for the degradation of two beta-blocker drugs, including Atenolol (AT) and Metoprolol (ME). Structural and morphological analyses of the catalysts were conducted, and optimal conditions for drug degradation were determined using a Box-Behnken design. The results underscored the significant influence of pH, catalyst amount, drug concentration, and H2O2 concentration on the degradation process using ZnO NPs/Zeolite and TiO2 NPs/Zeolite as the catalysts. The optimal values of drug concentration, pH, catalyst amount, and H2O2 concentration, were determined to be 32 and 33 mg L−1, 4.2 and 4.6, 428 and 386 mg, and 2.6 and 2.5 mM utilizing ZnO NPs/Zeolite and TiO2 NPs/Zeolite as the catalyst, respectively. Following optimization, the kinetics of the photodegradation process were investigated, revealing promising rates and half-life times for both drugs. The pseudo-first-order rate constants for Atenolol and Metoprolol degradation were 0.064 ± 0.007 min−1 and 0.065 ± 0.004 min−1 with ZnO NPs/Zeolite and 0.071 ± 0.007 min−1 and 0.071 ± 0.006 min−1 with TiO2 NPs/Zeolite, respectively. Furthermore, ZnO NPs/Zeolite and TiO2 NPs/Zeolite demonstrated reusability up to 5 and 6 times, respectively, without significant activity loss. The comparative analysis highlighted the superior performance of TiO2 NPs/Zeolite over ZnO NPs/Zeolite, attributed to lower consumption, shorter degradation time, improved reusability, and compatibility with milder acidic conditions. Overall, the research showcases the potential of ZnO NPs/Zeolite and TiO2 NPs/Zeolite as an effective and sustainable solution for removing Metoprolol and Atenolol contaminants.

Combined approach of nanoemulgel and microneedle pre-treatment as a topical anticellulite therapy

Background and purpose: Cellulite is caused by changes in the metabolism of the fatty tissue beneath the skin. Methylxanthines and retinoids are commonly added to the different anticellulite products. However, their topical permeation into the dermis is limited. Thus, the objective of this research is to formulate a nanoemulgel (NEG) containing a triple therapy of caffeine, aminophylline, and tretinoin as a topical anticellulite product to improve their skin permeation. Furthermore, the influence of microneedles (MNs) as skin pre-treatment on the permeation of the NEG was investigated. Experimental approach: Various nanoemulsion (NE) formulations were prepared using high-energy ultrasonication with different compositions and sonication amplitudes. Several characterisation tests were employed to select the optimum NE formulation. Then, the optimised NE formulation was incorporated with hyaluronic acid to prepare the NEG, which was, in turn, subjected to various evaluations. An ex vivo permeation study using human skin was performed for the NEG compared to a control preparation of plain gel. Additionally, a microneedling pen was applied as a skin pre-treatment at varying lengths prior to NEG application to examine its impact on the NEG’s permeation. Key results: The selected NEG has a homogenous and consistent texture with no coarse particles, a droplet size of 175.8 nm and polydispersity index (PDI) of 0.19, an optimum pH value of 5.28, high drug content of caffeine, aminophylline, and tretinoin (99.35, 98.48 and 98.05 %, respectively), high drug release values of approximately 100 % within 6 hours, appro-priate viscosity, minimum skin irritation, and adequate short-term stability. The ex vivo permeation study showed that caffeine, aminophylline, and tretinoin permeated more and deposited in the skin with higher percentages from the NEG than plain gel. This skin deposition within the dermis was increased by applying the microneedling pen at varying lengths of 0.5, 1, and 2 mm as a skin pre-treatment. Conclusion: This combined approach of NEG formulation containing a triple therapy of caffeine, aminophylline, and tretinoin, along with MNs application, has the potential to serve as a topical anticellulite product, reducing cellulite formation and improving skin appearance.

Stability of immobilized L-arginine deiminase from Penicillium chrysogenum and evaluation of its anticancer activity

The aim of the present work was to immobilize L-arginine deiminase on suitable supports such as chitosan, alginate, and silica gel to study its stability. Additionally, the study aims to investigate the anticancer effects of the free purified enzyme on hepatocellular carcinoma (Hep-G2) and breast cancer (MCF-7) cell lines. L-arginine deiminase (ADI: EC 3.5.3.6) was immobilized on chitosan, Ca-alginate, and silica gel, with immobilization efficiencies of 89.0%, 72.8%, and 66.5%, respectively. The optimal immobilization time for the highest efficiency was 4 h. Increasing the concentration of glutaraldehyde improved the immobilization efficiency of ADI on chitosan. The chitosan-immobilized ADI retained about 45% of its activity after 8 cycles. The optimal pH values were 6 for the free purified ADI and 7 for the chitosan-immobilized ADI. The optimal temperature increased from 40 °C for the free enzyme to 45 °C after immobilization. The activation energies for the free and chitosan-immobilized enzymes were 71.335 kJ/mol and 64.011 kJ/mol, respectively. The Km values for the free and chitosan-immobilized ADI were 0.76 mM and 0.77 mM, respectively, while the Vmax values were 80.0 U/mg protein for the free ADI and 71.4 U/mg protein for the chitosan-immobilized ADI. After 30 days of storage at 4 °C, the residual activities were 40% for the free purified ADI and 84% for the chitosan-immobilized ADI. At 25 °C, the residual activities were 10% for the free ADI and 75% for the chitosan-immobilized ADI. The chitosan-immobilized ADI exhibited significantly higher stability against proteases such as pepsin and trypsin compared to the free enzyme. The purified ADI also demonstrated enhanced potential anticancer effects and significant cytotoxicity against the Hep-G2 and MCF-7 tumor cell lines compared to doxorubicin. These findings suggest that purified ADI has potential as an anticancer agent, though further in-depth studies are required.

Integration of Coagulation–flocculation(with Natural Coagulant) to Constructed Wetlands for Color Removal from Tequila Vinasses

The aim of this study was to evaluate a natural coagulant, Moringa oleifera seeds (MOC), to reduce the color concentration in treated tequila vinasses (TVs). TV-A was the effluent of horizontal subsurface flow wetlands (HSSFW); TV-B was the effluent of vertical up-flow wetlands (VUFW); and TV-C was the effluent of vertical down-flow constructed wetlands (VDFW). Raw TVs were also with MOC. Jar tests were performed to find the optimal dose and pH value for apparent color (AC) removal. With the optimal dose and pH for each type of TV, tests were performed in triplicate to evaluate the removal of apparent color (AC), true color (TC), turbidity, total suspended solids (TSS), chemical oxygen demand (COD), and electrical conductivity (EC). For TV-A and TV-B, the optimal values were 1 g/L of MOC and pH 8, and the removals were 52%, 43%, 50% and 72% of AC, turbidity, TC, and TSS, respectively. For TV-C, the optimal values were 2.5 g/L and pH 5, with removals of 66%, 73%, and 98% for AC, TC, and TSS, respectively. For TV-D, the MOC had no coagulant effect in any of the experimental conditions evaluated, probably due to the high concentration of turbidity and TSS in the raw vinasses, which prevented the interaction between MOC and melanoidins. Deeper studies are required to understand and evaluate those factors that influence MOC efficiency so that the coagulation–flocculation process can be optimized.

Alterations in nitrogen metabolism caused by heavy metals in the acid-tolerant microalga Coccomyxa onubensis

The microalga Coccomyxa onubensis is an extremophile microorganism with a unique ecosystem (Río Tinto, Huelva, Spain) that contains high amounts of contaminants, including heavy metals, sulphates, and nitrates, in acidic environments (pH 2.5). The current work presents an evaluation of the capacity of Coccomyxa onubensis to assimilate different nitrogen sources under Cu2+, Cd2+, AsO33−, AsO43− and Hg2+ stress, and the metabolic implications of these stressors. The results showed that ammonium consumption was less affected than nitrate consumption when microalgae were cultivated with heavy metals (except cadmium). The activities of enzymes involved in nitrogen metabolism, such as nitrite reductase (NiR; EC:1.7.7.1), glutamine synthetase (GS; EC:6.3.2.1) and glutamate dehydrogenase (GDH; EC:1.4.1.2) were characterised to determine the Michaelis-Menten constant (Km) and optimal temperature and pH values, being 45, 40 and 60 °C and pH values of 7.5, 6.0 and 9.0 for NiR, GS, and GDH, respectively. The effects of different heavy metals on these enzymes were assessed at multiple levels, and the results showed that the enzymatic activity of NiR was downregulated, specially under copper stress, maintaining 23 % of control NiR activity at 2 mM Cu2+. The enzymatic activity of GS was upregulated at low concentrations under cadmium and mercury stress (115–120 % of control cultures GS activity at 25 μM Cd2+ and 50 nM Hg2+, respectively) and downregulated at high concentrations of these elements. GDH activity was upregulated in the presence of Cu2+, Cd2+, and Hg2+, with increases up to 192, 155 and 154 % at 1 mM Cu2+, 300 μM Cd2+, and 250 nM Hg2+, respectively. These results provide a better explanation of the effects of heavy metal stress on N metabolism in Coccomyxa onubensis, which may be used as a model eukaryotic organism of the Tinto River acidophilic ecosystem.

Obtaining and Characterizing Thermostable α-Amylases Secreted by Bacillus subtilis, Originating from Bacillus amyloliquefaciens and Bacillus subtilis

The production of recombinant enzymes, primarily used for obtaining pure and functional target molecules, holds significant importance in modern biotechnology. This study aimed to obtain and characterize recombinant, extracellularly expressed α-amylases (Amy3500 and Amy1974), derived from B. amyloliquefaciens MDC1974 and B. subtilis MDC3500, respectively, using the pBE-S shuttle vector. Both α-amylase genes were molecularly cloned into the E. coli/B. subtilis pBE-S shuttle vector, both with (Amy1974sig and Amy3500sig) and without their signal peptides (Amy1974 and Amy3500), along with a signal peptide originating from the plasmid, and tested in flask fermentations. For recombinant Amy3500, the amylase variants resulted in similar levels of volumetric activity (700–750 U/mL). In contrast, the expression of Amy1974 nearly doubled compared to Amy1974sig with double signal peptides, reaching 2000 U/mL. SDS-PAGE estimated the molecular weight of Amy1974 α-amylase to be 54.6 kDa, which is consistent with the theoretical molecular mass calculations. However, the estimated molecular weight of Amy3500 α-amylase was significantly lower upon exiting the producer cells. Ca2⁺ ions exhibit a modest activating effect on the activities of Amy1974 and Amy3500 amylases, likely due to their tight binding to the protein scaffold. Both enzymes exhibited broad activity peaks between 45 and 70 °C, with a maximum at 65 °C. The Amy1974 and Amy3500 α-amylases demonstrated broad pH optima and pH-dependent thermostability, with optimum pH values at 6.5 and 5.8, and thermal stability peaks at pH 7.6 and 5.9, respectively. Both α-amylases displayed high relative activity against various starches, including corn amylopectin and potato amylose, while showing comparatively lower activity towards α-, β-, and γ-cyclodextrins. The Amy1974 amylase is effective in converting starch into dextrins of varying lengths, while Amy3500 primarily converts starch into glucose. These characteristics make them promising candidate enzymes for industrial applications.

Evaluation of the soil quality using health index in temperate European conditions (Slovak Republic)

Land users and policy makers recognize importance of soil health and these types of evaluations are welcomed within sustainable land management. The aim of this study was to establish minimum and maximum values of soil health index across the breadth of agricultural used soils of Slovakia. Core objectives included (1) identifying the range of soil health benchmarks; (2) defining benchmarks for different land uses, and (3) defining benchmarks of soil health index for main groups of agricultural soils in Slovakia. These benchmarks represent the first soil health metrics of their kind in Slovakia using data from 266 locations. The soil health index (SHI) approach has been used as a quantitative tool to establish linkage between soil health and soil ecosystem services. We recorded the highest average SHI value in the very warm climatic region of the Slovak Republic, where the majority of agriculturally used arable soils (with an optimal pH value without contamination) are located. The locality with lowest SHI value is in a slightly warm area on soil used as arable soil with a very small depth of humus horizon, with by the pH value in an acidic area, and with a high content of clay. The typical SHI in humus-rich soil groups of Slovakia (Mollic Fluvisols, Chernozems and Cutanhic Luvisols) is higher contrasted with the typical SHI in other soil groups of Slovakia.

Feasibility of vanadium ion adsorption/desorption using nickel–aluminum complex hydroxides with different molar ratios

Herein, metal complex hydroxides containing nickel (Ni) and aluminum (Al) at different molar ratios (Ni:Al = 1:1 (NA11), 1:2 (NA12), 2:1 (NA21), 3:1 (NA31), and 4:1 (NA41)) were prepared. Scanning electron microscopy images, X-ray diffraction patterns, specific surface area, number of hydroxyl groups, and pHpzc were evaluated. Further, the adsorption capacity of vanadium ions was assessed, with NA21 showing a high potential to adsorb vanadium ions from the aqueous phase (177.5 mg/g). In addition, the effects of various factors, including pH, contact time, initial concentration, and temperature, on the adsorption of vanadium ions were demonstrated in this study using NA21. The optimal pH value for adsorbing vanadium ions was 5.0. Adsorption isotherms and kinetic data were fitted to a pseudo-second-order model (correlation coefficient: 0.958) and a Freundlich model (correlation coefficient: 0.930–0.982), respectively. This study elucidated that a part of the adsorption mechanism of vanadium was related to ion exchange and characteristics of NA21 surface. Moreover, NA21 showed capability to selectively adsorb vanadium ions from binary solution system containing chloride, nitrate, or sulfate ions. Vanadium ions adsorbed onto NA21 were more easily desorbed by a sodium hydroxide solution than a sodium sulfate solution. NA21 demonstrated consistent performance over at least three adsorption and desorption cycles under experimental conditions of this study. These findings provided valuable insights into the recovery of vanadium ions from aqueous media via adsorption/desorption treatment using NA21.

Extraction, Purification and Characterization of Poly Phenol Oxidase from Potato and Apple and Inhibition of Enzymatic Browning

The purpose of this study was to determine the optimum conditions for the extraction of polyphenol oxidase (PPO) from potato and apple. PPO is found in a variety of fruits and vegetables and is the enzyme that causes browning reactions when handling damaged cells. At 405 nm, the enzyme activity was determined using spectrophotometry. PPO was researched to stop potato and apple from browning, which reduces their marketability. The outcomes showed that using an extraction buffer containing phosphate buffer (0.05 M, pH 6.6) was the optimum condition for the extraction of polyphenol oxidase from potato and apple. In addition, the results showed that as the temperature increased, the (PPO) activity increased, and the activity reached its peak at a temperature of 35 ͦC. The optimum pH value of (PPO) activity was 6.5 and we observed during the research that (PPO) decreased in strong acid condition and alkaline environments. Moreover, the results showed that the highest activity of polyphenol oxidase enzyme extracted from apple and potato was by using (O-dihydroxybenzene) as a substrate. As the concentration of the substrate increased, the (PPO) activity increased, reaching the optimum substrate concentration of 0.8%, and then its activity decreased. Also, we found that when using ascorbic acid, citric acid, and Na2SO3 as inhibitors, the activity of the polyphenol oxidase enzyme decreased with an increase in the concentration of ascorbic acid, citric acid, and Na2SO3. Sodium thiosulfate, 0.01 M ascorbic acid and 0.5% polyethylene glycol were extracted with an extraction ratio of 1:4 (w/v) for three minutes by using a blender. The purpose of study was to determine the optimum conditions for polyphenol oxidase extraction from potato and apple.

Effect of Thiophene-Hydrazinyl-Thiazole derivative as an efficient dye sensitizer and performance enhancer of TiO2 toward rhodamine B photodegradation

Visible-light-driven photocatalysis is an eco-friendly technology for wastewater treatment, where TiO2-based photocatalysts displayed outstanding performance in this regard. Dye sensitization is a promising approach for overcoming the common drawbacks of TiO2via improving its photocatalytic performance and extending its activity to visible light. Herein, we demonstrate the synthesis of the Thiophene-Hydrazinyl-Thiazole (THT) derivative as a novel organic dye sensitizer to be employed as a visible-light antenna for TiO2 nanoparticles. The physicochemical characteristics of the as-synthesized TiO2-based nanoparticles are examined by different techniques, which revealed the successful fabrication of the proposed THT-TiO2 heterojunction. The incorporation of THT molecules on the TiO2 surface led to slight disorders and deformation in the crystal lattice of TiO2, a remarkable improvement of its absorption in the visible light as a perfect visible-light antenna in the whole visible region, and significant enhancement in the charge transfer. Rhodamine B (RhB) is used as an organic dye model to assess the photocatalytic efficiency of the as-fabricated THT-TiO2 photocatalyst which achieved almost complete degradation (>95% in 150 min) with an observed rate constant (kobs) of 0.0164 min−1; total organic carbon (TOC) measurements suggested ∼75% mineralization. THT-TiO2 achieved 2.1-fold enhancement in photodegradation% and 4.1-fold enhancement in kobs compared to the bare TiO2. THT showed good activity under visible-light irradiation (RhB degradation% was >66% in 150 min and kobs = 0.0085 min−1). The influence of the initial pH of the solution was investigated and pH 4 was the optimum pH value for suitable interaction between RhB and the surface of THT-TiO2. Radical quenching experiments were conducted to assess the crucial reactive species where the ∙OH and O2.− were the most reactive species. THT-TiO2 showed promising stability over three successive cycles. Finally, the improvement mechanism of the photocatalytic activity of THT-TiO2 was attributed to the electron injection from the excited THT (the dye sensitizer) to TiO2 and enhanced charge separation.

OPTIMIZATION OF pH VALUE AND GEL VISCOSITY IN PORANG TUBER CAPSULE SHELL FORMULATION

The porang tuber contains glucomannan compounds that can expand into a gel so that it has the potential to be used as the main ingredient of capsule shells. This research aims to optimize the pH and viscosity values that can affect the consistency of the capsule shell produced. The method used in the manufacture of capsule shells is the dipping pen method, while the optimization method carried out is trial and error by making 3 formulas by combining glycerin and PEG 400. The results obtained by the gel mass formed by the glycerin-PEG 400 gelling agent have a viscosity value of 586.67 dPas and a pH value of 6.02 can provide a gel mass that is easy to mold capsule shells and obtain capsule shells with elastic characters. The results indicate optimal viscosity and pH values to obtain a gel mass that is easy to mold capsule shells with good organoleptic characteristics. Keywords: Glucomannan, pH, viscosity, capsule shell.

Development of a Hydrometallurgical Process for the Extraction of Cobalt, Manganese, and Nickel from Acid Mine Drainage Treatment By-Product

Critical minerals (CMs) are pivotal in modern industries, such as telecommunications, defense, medicine, and aerospace, contributing significantly to regional and global economic growth. However, the reliance on external sources for 26 out of 50 identified CMs raises concerns about supply chain vulnerabilities. To address this, the research focused on developing a hydrometallurgical process for extracting cobalt, manganese, and nickel from acid mine drainage (AMD) treatment by-products, emphasizing the need to diversify CM supply chains within the United States (US). A solution composed of an REE solvent extraction raffinate loaded with cobalt, manganese, nickel, and various impurity metals was utilized as a feedstock in this study. The developed hydrometallurgical process involved initial sodium hydroxide precipitation to remove impurities like aluminum and iron from an SX raffinate solution generated during the extraction of rare earth elements (REEs). Precipitation stages were performed in a pH region ranging from 2 to 12 to identify the optimum pH values, achieving a tradeoff between recovery and impurity removal. A subsequent precipitation process at pH 5–10 yielded a product rich in CMs, such as manganese, cobalt, and nickel. Further separation steps involved nitric acid washing, resulting in a Mn product with a purity of 47.9% by weight and a solution with extractable concentrations of cobalt and nickel. Stagewise precipitation with sodium sulfide subsequently produced three solid products: cobalt and nickel product at pH 1–5, manganese product at pH 5–10, and magnesium at pH 10–12. The study also explored other separation approaches, including solvent extraction, to enhance the separation of nickel from cobalt. Overall, the developed hydrometallurgical process generated the following products with varying degrees of purities: cobalt (9.92 wt.%), nickel (14 wt.%), manganese (47.9 wt.%), and magnesium (27.49 wt.%). This research aimed to contribute to the sustainable extraction of CMs from secondary sources, reducing the US’ reliance on imports and promoting a more resilient supply chain for these crucial elements.

Comparative Analysis of the Recovery of Cu2+ and Au from Washing Solution of Pyrite Concentrate Slag by Two Processes

A large amount of pyrite concentrate slag washing solution is produced in China every year, and this contains valuable components such as Cu2+ and Au. The traditional treatment method not only pollutes the environment but also wastes metal resources. For the washing solution containing Cu2+ 437 mg/L and Au 0.13 mg/L, two new processes comprehensive recovery schemes were developed and compared in this paper, namely iron powder replacement pore filtration and neutralization precipitation pore filtration. When the iron powder replacement pore filtration process was adopted, Cu2+ and Au were mainly comprehensively recovered in the form of a mixture of sponge copper and particulate gold. The test results showed that the replacement optimal conditions involved a pH of 3.0, iron powder dosage of 6 g/L, and replacement time of 3.0 h. After replacement, the filter cloth with below 1 μm pore size was used for filtration. The recovery rate of Cu2+ in the washing solution was 98.13 and the total recovery rate of Au was 95.83%. Otherwise, when the neutralization precipitation pore filtration process was adopted, Cu2+ and Au were mainly comprehensively recovered in the form of a mixture of copper hydroxide and particulate gold. The test results showed that sodium hydroxide was used as the precipitant and the optimum neutralization pH value was 6.5. After precipitation, the filter cloth with a below 1 μm pore size was used for filtration. The recovery rate of Cu2+ in the washing solution was 97.35% and the total recovery rate of Au was 93.54%. The economic benefit estimation of the two processes showed that the neutralization precipitation pore filtration process had the advantages of low material consumption, low cost and high economic benefit.

Evaluation of the Amount of Endophytic Bacteria Associated with Roots of Brachiaria Humidicola Cv. Humidicola (Rendle) Schweick in Relation to Ph Values, Organic Matter and Phosphorus Contents of Cattle Farm Soil

The objective of this study was to isolate endophytic bacteria from roots of Brachiaria humidicola cv. humidicola (Rendle) Schweick and to relate their presence to pH, organic matter and phosphorus contents of the soil of cattle farms located in the municipality of San Benito Abad. Soil sampling was carried out with roots of B. humicola for the isolation and counting of the population density of endophytic bacteria and soil samples were also collected for the determination of pH, organic matter and phosphorus parameters. The results found indicate that there is an amount of endophytic bacteria in roots of B. humidicola when the soil contains optimum pH values of (6.1 ± 6.98); low to moderate phosphorus content (10.8 ± 16.28 mg/kg) and low to moderate organic matter content (1.7 ± 2.31%). The presence of endophytic bacteria was observed in a range of 3.0 ± 8.0 X 106 CFU/g of roots. There is a worldwide need to establish a relationship between endophytic bacteria and soil physical-chemical quality indicator parameters to predict a change in functional diversity under physical, chemical and biological conditions of the soil ecosystem.

Comparative study of un-doped CeO2 and metal (Mn, Co, Fe)-doped CeO2 nanostructures for the removal of golden yellow dye from synthetic wastewater

ABSTRACT In this study, the activity of un-doped cerium oxide (CeO2) nanostructure with metal (Mn, Co, Fe)-doped CeO2 nanostructures was compared as effective scaffolds for the elimination of Golden Yellow (GY) Dye. For this purpose, the un-doped and doped-CeO2 nanostructures were prepared through co-precipitation treatment and characterised using the following techniques like FTIR, XRD, UV, PL, SEM and EDX analysis. The synthetic nanostructures were selected for the removal of GY through adsorption and photocatalytic degradation from wastewater. Tauc’s model was employed to determine the optical band gap, and various key parameters (contact duration, pH, nanostructure dosage and GY concentration) were optimised for the adsorption/photocatalytic degradation of GY. The adsorption and degradation processes for these nanostructures were found to be pH-dependent, with an optimum pH value of 4. UV–visible spectroscopy was employed to probe the GY adsorption followed by the GY degradation, revealing a higher removal and degradation efficiency of 39.89% and 58.46% for Mn-CeO2, 34.60% and 47.21% for Co-CeO2 and 31.67% and 39.10% for Fe-CeO2 compared to 14.05% and 30.37% for un-doped CeO2, respectively. In total, 98.35% of GY removal was achieved by Mn-CeO2 compared to 44.42% by un-doped CeO2 within 175 min via adsorption (50 min) followed by degradation (125 min). Additionally, the absorption mechanism underwent analysis, with the kinetic data aligning closely with the pseudo-first-order model. Examination of the adsorption capacity at various equilibrium concentrations of the dye solution revealed the formation of monolayers and chemisorption phenomena. Moreover, the rate constant dropped when scavengers like ethylenediaminetetraacetic acid (EDTA), isopropyl alcohol (IPA), and hydrogen peroxide (H2O2) were added because they capture holes (h+), hydroxyl radicals (·OH), and superoxide radicals (·O2 −) respectively, with EDTA showing more prominent effects.

Methylene blue and Congo red dye elimination from synthetic wastewater using Albizia lebbeck seed pod powder: isotherm and kinetic and mechanistic studies

This research examined the effectiveness of using Albizia lebbeck seed pods (ALB) as an adsorbent to remove dye effluents and clean up wastewater. More specifically, the binding capacity of methylene blue (MB) and Congo red (CR) dyes from aqueous solution using unmodified Albizia lebbeck seed pods (UALB) and citric acid modified Albizia lebbeck seed pods (CALB) were compared. The adsorbents underwent characterization via the use of Fourier transform infrared spectroscopy and scanning electron microscopy. Several operational factors were investigated using batch tests to ascertain their effects. These parameters included pH, adsorbent dose, interaction duration, and initial dye concentration. The residual dye concentrations were determined, and the data generated were fitted to equilibrium and kinetic models. In CALB and UALB, MB adsorption ideal pH values were 10 and 12, whereas CR optimal pH values were 3 and 2. Also, MB and CR equilibrium durations were 360 and 240 min, respectively. Temkin model best described the adsorption in CALB ( r 2 = 0.9916, 0.9484) whereas Freundlich worked well for UALB in MB and CR ( r 2 = 0.9626, 0.9871). Kinetic modeling of the adsorption data showed that the pseudo-second-order kinetic model provided the best fit ( r 2 = 0.9998, 0.9999) for CALB and ( r 2 = 1, 0.9992) for UALB for both MB and CR dyes. Maximum adsorption for MB was 9.499 mg/g and for CR it was 8.628 mg/g, and the findings showed a positive linear correlation between the concentration of dye-ions and their adsorption ability. The CALB also demonstrated superior efficacy in the removal of MB (4.661 mg/g) dye relative to CR (4.113 mg/g). The results of this study demonstrate that the use of ALB, in both modified and unmodified forms, is a cost-effective and efficient approach for the removal of MB and CR from the aqueous environment.

Enzymatic phenolics removal by tyrosinase-modified micromotors

In this study, self-propelled Pt/PPy-COOH micromotors were produced by using the sequential electrodeposition of Pt and PPy segments. Fabricated micromotors were modified with tyrosinase enzyme and was used to investigate the phenolic compound removal capacity. The micromotors was characterized by SEM and EDX analyses, and it was found that the shape of the motors was tubular and 10 µm long. The optimum pH values of free and immobilized enzymes were found to be 7.5, while the optimum temperature values were 45 °C. In the thermal stability study, it was determined that the immobilized enzyme showed 75 % activity after 5 h, while the activity of the free enzyme was around 21 %. Also, immobilized tyrosinase showed 55 % activity after 10 repeated uses. Finally, the phenol, p-cresol and o-phenylenediamine removal efficiencies of tyrosinase-based micromotors were found to be 54.54 %, 46.96 % and 53.87 % in 5 min, respectively. As a result, it can be concluded that it is possible to use tyrosinase-based micromotors as an alternative to traditional methods for phenol removal.

Sensitive electrochemical determination of quercetin and folic acid with cobalt nanoparticle functionalized multi-walled carbon nanotube.

A nanocomposite of cobalt nanoparticle (CoNP) functionalized carbon nanotube (Co@CNT) was prepared and used to modifyaglassy carbon electrode (Co@CNT/GCE). Characterization indicates the morphology of Co@CNT is CoNPs adhering on CNTs.With the nano-interface, Co@CNT provideslarge surface area, high catalytic activity, and efficient electron transfer, which makes Co@CNT/GCE exhibiting satisfactory electrochemical response toward quercetin (QC) and folic acid (FA).The optimumpH values for the detection of FA and QC are 7.0 and 3.0, respectively. The saturated absorption capacity (Γ*) and catalytic rate constant (kcat) of Co@CNT/GCE for QC and FA are calculated as 1.76 × 10-9, 3.94 × 10-10mol∙cm-2 and 3.04 × 102, 0.569 × 102M-1∙s-1. The linear range for both FA and QC is estimated to be 5.0nM-10μM, and the LODs (3σ/s) were 2.30nM and 2.50nM, respectively. The contents of FA and QC in real samples determined by Co@CNT/GCE are comparable withthe results determined by HPLC. The recoveries were in the range 90.5 ~ 114% and the total RSD was lower than 8.67%, which further confirms the reliability of the proposed electrode for practical use.

H2S mitigation for biogas upgrading in a full-scale anaerobic digestion process by using artificial neural network modeling

Biogas production by anaerobic digestion (AD) has emerged as a prominent bio-renewable energy source in recent years. However, the process also produces undesirable by-products, including H2S, thereby negatively impacting the biogas quality. This study focused on mitigating H2S in a full-scale AD located at a wastewater treatment plant (WWTP) by controlling the internal operational parameters by using an artificial neural network (ANN) model. Data from 54 days of AD operation were used to train and validate a structured ANN with a 5-3-1 topology. To minimize the H2S content, optimum values for dry solid (DS), volatile solid (VS), pH, temperature, and primary sludge fraction (PS) were determined to be 6.2 %, 63 %, 7.7, 35.6 °C, and 67.6 %, respectively, using the particle swarm optimization (PSO) algorithm. This optimization indicated a 49 % reduction in the average H2S concentration, from 6117 ppm to 3107 ppm. The analysis of relative importance (RI) showed that the pH (RI = −29.5) and PS (RI = −28.7) were the most critical factors affecting biogas quality. Additionally, several solutions derived from the optimization results were practically implemented in the Qom WWTP to achieve optimal conditions, and the outcomes were discussed.

Optimalisasi Penggunaan Fly Ash Untuk Reduksi Kadar Besi (Fe) Dan Mangan (Mn) Serta Peningkatan pH Dalam Air Asam Tambang

Coal mining activities often result in acid mine drainage (AMD), which can cause environmental pollution if not properly managed. This study aims to evaluate the potential use of fly ash from the Stream Power Plant (PLTU) Tenggarong to mitigate the impacts of AMD, specifically targeting iron (Fe), manganese (Mn), and pH parameters. Acid Mine drainage is formed when sulfide minerals oxidize, producing acidic compounds that can harm the environment. This research focuses on analyzing the ability of fly ash to adsorb iron and manganese from AMD solutions, as well its capability to increase solution pH. Based on the conducted research, the optimum pH value was achieved when using 10 grams and 15 grams of fly ash in the adsorption process. The optimum concentration of iron (Fe) was attained using 10 grams to 15 grams of fly ash, while for manganese (Mn), it was achieved with 20 grams to 25 grams of fly ash. The adsorption process using 25 grams of fly ash showed the highest efficiency in reducing iron (Fe) concentration by 93.78 % and manganese (Mn) concentration by 75.47 %.