Optimum Conditions pH Research Articles

Nanocellulose-Based Ecofriendly Nanocomposite for Effective Wastewater Remediation: A Study on Its Process Optimization, Improved Swelling, Adsorption, and Thermal and Mechanical Behavior.

A nanocellulose (NC)-based cross-linked adsorbent has been employed herein for the removal of dye pollutants (e.g., methylene blue) from the textile industry. The synthesized hydrogel was optimized to achieve the best concentrations of the adsorbent constituents, i.e., 1.55% guar gum, 1.46% NC, and 0.84% borax for achieving the maximum swelling index (SI, 3741.42%) and higher adsorption capacity (qe, 24.05 mg g-1). 98.8% of dye qe was achieved at optimal conditions of pH 8 within 30 min at 30 °C. Adsorption isotherms and kinetics investigations showed good correlation with the Freundlich adsorption isotherm model (R2 > 0.9889; ΔG° = -4.71; ΔH° = -12.30; ΔS° = -0.025) as well as the pseudo-second-order kinetics model, indicating multilayered and intricate adsorption mechanisms for dye removal. The study of thermodynamic parameters confirmed the exothermic nature of the adsorption process. The adsorption-desorption study of the resulting hydrogel exhibited 64.58% dye removal efficiency even after 4 consecutive cycles of reuse. Further, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction analysis revealed the surface morphology, functional moieties, thermal behavior, and crystallinity pattern of the hydrogel. Rheological analysis demonstrated pseudoplastic flow and improved mechanical behavior for the hydrogel. The current study found that the synthesized adsorbent with a higher SI and qe has a noticeable potential for the removal of dye pollutants from wastewater.

Confinement and Polarity Effects on the Peptide Packing Density on Mesoporous Silica Nanoparticles.

The adsorption of cationic peptide JM21 onto different mesoporous silica nanoparticles (MSNs) from an aqueous solution was studied as a function of pH. In agreement with the literature, the highest loading degrees could be achieved at pH close to the isoelectric point of the peptide where the peptide-peptide repulsion is minimum. However, mesopore size, mesopore geometry, and surface polarity all had an influence on the peptide adsorption in terms of both affinity and maximum loading at a given pH. This adsorption behavior could largely be explained by a combination of pH-dependent electrostatic interactions and confinement effects. It is demonstrated that hydrophobic interactions enhance the degree of peptide adsorption under pH conditions where the electrostatic attraction was absent in the case of mesoporous organosilica nanoparticles (MONs). The lower surface concentration of silanol groups for MON led to a lower level of peptide adsorption under optimum pH conditions compared to all-silica particles. Finally, the study confirmed the protective role of MSNs in preserving the biological activity of JM#21 against enzymatic degradation, even for large-pore MSNs, emphasizing their potential as nanocarriers for therapeutic peptides. By integrating experimental findings with theoretical modeling, this research elucidates the complex interplay of factors that influence peptide-silica interactions, providing vital insights for optimizing peptide loading and stabilization in biomedical applications.

Support Materials of Organic and Inorganic Origin as Platforms for Horseradish Peroxidase Immobilization: Comparison Study for High Stability and Activity Recovery.

In the presented study, a variety of hybrid and single nanomaterials of various origins were tested as novel platforms for horseradish peroxidase immobilization. A thorough characterization was performed to establish the suitability of the support materials for immobilization, as well as the activity and stability retention of the biocatalysts, which were analyzed and discussed. The physicochemical characterization of the obtained systems proved successful enzyme deposition on all the presented materials. The immobilization of horseradish peroxidase on all the tested supports occurred with an efficiency above 70%. However, for multi-walled carbon nanotubes and hybrids made of chitosan, magnetic nanoparticles, and selenium ions, it reached up to 90%. For these materials, the immobilization yield exceeded 80%, resulting in high amounts of immobilized enzymes. The produced system showed the same optimal pH and temperature conditions as free enzymes; however, over a wider range of conditions, the immobilized enzymes showed activity of over 50%. Finally, a reusability study and storage stability tests showed that horseradish peroxidase immobilized on a hybrid made of chitosan, magnetic nanoparticles, and selenium ions retained around 80% of its initial activity after 10 repeated catalytic cycles and after 20 days of storage. Of all the tested materials, the most favorable for immobilization was the above-mentioned chitosan-based hybrid material. The selenium additive present in the discussed material gives it supplementary properties that increase the immobilization yield of the enzyme and improve enzyme stability. The obtained results confirm the applicability of these nanomaterials as useful platforms for enzyme immobilization in the contemplation of the structural stability of an enzyme and the high catalytic activity of fabricated biocatalysts.

Extraction, Purification, and Characterization of Olive (Olea europaea L., cv. Chemlal) Polyphenol Oxidase.

Among fruits susceptible to enzymatic browning, olive polyphenol oxidase (OePPO) stood out as being unisolated from a natural source until this study, wherein we successfully purified and characterized the enzyme. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of heated and nonheated OePPO revealed distinct molecular weights of 35 and 54 kDa, respectively, indicative of its oligomeric nature comprising active and C-terminal subunits. OePPO displayed latency, fully activating with 5 mM SDS under optimal conditions of pH 7.5 and 15 °C. The enzyme demonstrated monophenolase activity and showcased the highest efficiency toward hydroxytyrosol. Despite its low optimal temperature, OePPO exhibited high thermal resistance, maintaining stability up to 90 °C. However, beyond this threshold, the oligomeric enzyme disassociated, yielding a denatured main subunit and C-terminal fragments. Six OePPO genes were found in the fruits. Tryptic digestion identified the enzyme as mature OePPO1 (INSDC OY733096), while mass spectrometry detected the active form mass alongside several C-terminal fragments, revealing potential cleavage sites (Gly407, Tyr408).

Fabrication of Carbon Paste Electrode Modified with Bentonite Nanoparticles and Titanium Dioxide Nanoparticles for Analysis of Methyl Parabens by Cyclic Voltammetry

Cosmetics are products of several substances or ingredients with a predetermined time limit. Efforts to extend the time limit of cosmetic use are made by adding preservatives. One preservative that is often used is methylparaben. Methylparaben has been tested using spectrophotometry, voltammetry, and HPLC. In this study, electrode modification was carried out in the voltammetry test to obtain a low detection limit. The purpose of this study was to determine the effect of the working electrode composition of carbon paste, bentonite nanoparticles, titanium dioxide nanoparticles, and paraffin on the best response in the analysis of methylparaben by cyclic voltammetry, knowing the optimum measurement conditions of pH with the best electrode composition in the analysis of methylparaben by cyclic voltammetry. FTIR characterized bentonite nanoparticles to determine vibrations and functional groups, and XRD was performed to determine the phase and particle size. The electrode was made from a mixture of carbon, bentonite nanoparticles, titanium dioxide nanoparticles, and paraffin. The best electrode composition was added with titanium dioxide nanoparticles to obtain a higher peak current. XRD characterization of bentonite nanoparticles showed an average particle size of 43.8155 nm. The result of determining the best electrode composition is 3:2:3:2 with an anodic peak current of 9.6.10-4 A. The best methylparaben measurement at pH seven solution conditions. The latest research shows that carbon paste electrodes modified with bentonite and titanium dioxide nanoparticles can be used for methylparaben analysis.

Efficient flocculation pretreatment of coal gasification wastewater by halophilic bacterium Halovibrio variabilis TG-5.

The isolated halophilic bacterial strain Halovibrio variabilis TG-5 showed a good performance in the pretreatment of coal gasification wastewater. With the optimum culture conditions of pH = 7, a temperature of 46°C, and a salinity of 15%, the chemical oxygen demand and volatile phenol content of pretreated wastewater were decreased to 1721mg/L and 94mg/L, respectively. The removal rates of chemical oxygen demand and volatile phenol were over 90% and 70%, respectively. At the optimum salinity conditions of 15%, the total yield of intracellular compatible solutes and the extracellular transient released yield under hypotonic conditions were increased to 6.88g/L and 3.45g/L, respectively. The essential compatible solutes such as L-lysine, L-valine, and betaine were important in flocculation mechanism in wastewater pretreatment. This study provided a new method for pretreating coal gasification wastewater by halophilic microorganisms, and revealed the crucial roles of compatible solutes in the flocculation process.

Optimisation and economic analysis of industrial-scale anaerobic co-digestion (ACoD) of palm oil mill effluent (POME) and decanter cake (DC) using machine learning models: A comparative study of Gradient Boosting Machines (GBM), K-nearest neighbours (KNN), and random forest (RF)

The anaerobic co-digestion (ACoD) of palm oil mill effluent (POME) with decanter cake (DC), has been proposed as a solution to enhance biogas production in industrial-scale anaerobic covered lagoon systems. Despite the potential of ACoD, there is a limited exploration of machine learning techniques, such as Gradient Boosting Machines (GBM), K-nearest neighbours (KNN), and Random Forest (RF), specifically in the context of industrial-scale facilities and anaerobic co-digestion. In this study, these machine learning techniques were employed to develop prediction models for biogas production and BOD removal using three months of operational data from a local biogas plant, with GBM yielding the highest prediction accuracy (R2 = 0.9940, MAE = 0.0101, RMSE = 0.1438). Subsequently, GBM was used in the optimisation process to determine the optimal conditions for temperature, pH, and dilution ratio of DC in the anaerobic digester. The optimal conditions were found to be 40 °C, 7.1, and 0.11, respectively, representing a 21.58 % and 26.03 % increase in biogas production and BOD removal. This integrated approach provides a sustainable solution for maintaining year-round biogas production even when the supply of POME is limited, thereby contributing to renewable energy generation and waste management in the palm oil industry.

Valorization of Pine Cones (Pinus nigras) for Industrial Wastewater Treatment and Crystal Violet Removal: A Sustainable Approach Based on Bio-Coagulants and a Bio-Adsorbent

Pine cones are a widely available and abundant natural resource in Algeria, and they are rich in active molecules. This study investigated the valorization of Pine cones as a natural and abundant bio-coagulant in raw form (powder) and extract form. The active components of the Pine cones were extracted using two solvents, distilled water (DW) and NaCl, to obtain coagulants (proteins, polyphenols, and carbohydrates) for the treatment and improvement of industrial water quality parameters (discharge from a processing plant and tomato production) and an adsorbent (residue extract, RE). The recovered bio-coagulant was used to remove turbidity, chemical oxygen demand (COD), and zeta potential. The formed adsorbent was used to remove crystal violet (CV). Coagulation-flocculation experiments were carried out in a jar test to evaluate the performance of the coagulant in powder and extract form. The use of pine cone powder (PCP), extract using NaCl (PC-NaCl), and extract using DW (PC-DW) resulted in turbidity reductions of 96%, 94%, and 98%, respectively. For the residue recovered after extraction, a CV removal percentage of 99.9% was achieved at the optimal conditions of pH 10, CV concentration of 20 mg/L, adsorbent dose of 20 mg/L, and contact time of 120 min, as determined using the Box–Behnken design (BBD). Furthermore, all the effects were significant in the process of the CV phase adsorption on the bio-adsorbent. The model designed for optimal design fit the experimental data well, with a coefficient of determination, R2, of 0.965 and an Adj-R2 of 0.926. The p-value of this model was 0.000, which indicated that the model was very significant. This confirmed the effectiveness of the bio-adsorbent in removing dyes from water.

Design of chitosan/boehmite biocomposite for the removal of anionic and nonionic dyes from aqueous solutions: Adsorption isotherms, kinetics, and thermodynamics studies

This study introduces a chitosan/boehmite biocomposite as an efficient adsorbent for removing anionic Congo Red (CR) and non-ionic Bromothymol Blue (BTB) from water. Boehmite nanoparticles were synthesized using the Sol-gel method and then attached to chitosan particles using sodium tripolyphosphate through co-precipitation method. Characterized through FTIR, FE-SEM, BET, and XRD, the biosorbent displayed structural integrity with optimized pH conditions of 3 for CR and 4 for BTB, achieving over 90 % adsorption within 30 min. Pseudo second order kinetics model and Langmuir isotherm revealed monolayer sorption with capacities of 64.93 mg/g for CR and 90.90 mg/g for BTB. Thermodynamics indicated a spontaneous and exothermic process, with physisorption as the primary mechanism. The biosorbent demonstrated excellent performance and recyclability over five cycles, highlighting its potential for eco-friendly dye removal in contaminated waters.

Removal of Ibuprofen and Diclofenac using Azadirachta indica leaves extract modified with Iron oxide

Plant-based adsorbents have the potential to replace commonly used chemical adsorbents due to their cost effectiveness, eco-friendly and non-toxic properties. In this study, the adsorption potential of green synthesized iron-oxide particles, using neem (Azadirachta indica) leaves extract, was evaluated as a novel adsorbent for the removal of ibuprofen and diclofenac. The optimization of treatment factors for experimental design was undertaken via the Taguchi method. The adsorbent’s characterization was performed by the employment of Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy. Four adsorption factors were kept under consideration during experimental runs for each drug; initial concentration (10–40 ppm), contact time (10–40 min), pH level (3–9), and adsorbent dosage (0.1–0.4 g/L). Maximum removal efficiency as indicated by the results, was 81.89% for ibuprofen and 80.82% for diclofenac, achieved at optimum conditions of pH 5, 40 ppm initial concentration, 40 min contact time, and 0.3 g/L adsorbent dose. Among the adsorption factors, pH and initial concentration were observed to exert the greatest influence on the removal efficiencies for both drugs. The maximum adsorption capacity of adsorbent was 81.96 mg/g and 81.46 mg/g for diclofenac and ibuprofen, respectively. Freundlich isotherm fitted best to the removal both pharmaceutical compounds. The adsorbent used in this study demonstrated significantly higher removal potential and adsorption capacity for diclofenac and ibuprofen as compared with previously used adsorbents.

Catalytic removal of malachite green from aqueous solution by a peroxidase-mimicking Cu-Al layered double hydroxide nanoparticle: Synthesis, characterization, and application

Nanozymes are nanomaterials with inherent enzyme-like activities that have recently received much attention due to their high catalytic activity, low cost, and high stability. This research aimed to investigate the applicability of copper-aluminum layered double hydroxide (CuAl-LDH) for the catalytic decolorization of malachite green (MG). The enzyme-mimic activity of the prepared particles was tested using a colorimetric approach based on the oxidation of 3,3', 5,5'-tetramethylbenzidine (TMB) with hydrogen peroxide (H2O2), which results in the production of a blue-colored product with maximum absorption at 652 nm. The impact of different factors, including pH, temperature, TMB, and H2O2 concentrations, on the catalytic performance of CuAl-LDH was assessed. The kinetic parameters (Km and Vmax) were obtained to be 14.3 × 10−3 mM and 96.1 × 10−8 M/s (for TMB), and 0.05 × 10−3 mM, and 71.9 × 10−8 M/s (for H2O2), respectively. Compared to natural horseradish peroxidase (HRP), CuAl-LDH showed a high affinity for H2O2 and TMB. In addition, the results showed that CuAl-LDH could decolorize MG by 100% under optimum conditions of pH 4, 3.42 µM MG, and 4 mg/mL CuAl-LDH at 50 °C and within 13 min. These findings demonstrate the potential of CuAl-LDH, with intrinsic peroxidase-mimic activity, to decolorize and detoxify MG from industrial wastewater.

Porous reticular Co@Fe metal-organic gel: dual-function simulated peroxidase nanozyme for both colorimetric sensing and antibacterial applications.

Constructing metal-organic gels (MOGs) with enzyme-catalyzed activity and studying their catalytic mechanism are crucial for the development of novel nanozyme materials. In this study, a Co@Fe MOG with excellent peroxidase activity was developed by a simple and mild one-pot process. The results showed that the material exhibited almost a single peroxidase activity under optimal pH conditions, which allowed it to attract and oxidize the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB). Based on the active electron transfer between the metal centers and the organic ligand in the synthetic material, the Co@Fe MOG-H2O2-TMB system was verified to be able to detect H2O2 and citric acid (CA). The catalytic microenvironment formed by the adsorption and the catalytic center accelerated the electron-transfer rate, which expedited the generation of hydroxyl radicals (˙OH, a kind of reactive oxygen species (ROS)) in the presence of H2O2. The persistence and high intensity of ˙OH generation were proven, which would endow Co@Fe MOG with a certain antibacterial ability, promoting the healing of bacteria-infected wounds. In conclusion, this study contributes to the development efforts toward the application systems of nanozymes for marker detection and antibacterial activity.

Modified spectrophotometry for micromolar H2O2 determination in iron-containing solutions with leuco crystal violet under both aerobic and anaerobic conditions.

Accurately quantifying hydrogen peroxide (H2O2) is essential for elucidating its role across diverse environments. Spectrophotometry is widely employed in laboratories for this purpose due to its convenience, cost-effectiveness, and low detection limits for micromolar H2O2 concentrations. However, accurate measurement of H2O2 in iron-containing solutions presents challenges due to the interference of iron ions. In this study, we propose a modified spectrophotometric method for H2O2 determination in iron-containing solutions by adding two types of iron ion chelators and selecting leuco crystal violet (LCV) as a chromogenic reagent due to its stability. By sequentially adding 1,10-phenanthroline and EDTA, and using a phosphate buffer at pH 4.2 to provide the optimal chromogenic pH condition, this modified method effectively mitigates the interference of iron ions in the LCV chromogenic reaction. The applicability of this method under aerobic and anaerobic conditions was confirmed by comparing the experimental results with theoretical simulations. Under optimal chromogenic conditions, this method achieves a detection limit of 300 nM. This improved method allows better detection of H2O2 in iron-containing systems and investigation of its significance in various environmental processes.

Bio-based iron oxide nanoparticles forming bi-functional chitosan composite adsorbent for Cr(VI) decontamination

Iron oxide nanoparticles (IONPs) synthesized in a bio-based route are viable contenders for the removal of Cr(VI) from contaminated water. However, recovery and reuse of these IONPs are challenging and could limit their practical applicability. Herein, reusable and bi-functional composite chitosan (CS) beads (CS/IONPs) are developed by infusing IONPs in the CS matrix and applied for Cr(VI) adsorption and detoxification from synthetic wastewater. CS/IONPs beads were characterized through various analytical techniques: X-ray diffraction, X-ray photoelectron spectroscopy and Scanning electron microscopy. The loading of IONPs varied from 0.1 to 0.25 (% w/v) with Fe(III)/Fe(II) in a molar ratio of 2. Mesoporous (11.65 nm) CS/IONPs beads with a size from 6.6 − 4.31 mm were formed with a specific surface area of 63.67 m2/g compared to 25.42 m2/g for CS beads. Cr(VI) removal of 98.71 % was achieved by CS/IONPs adsorbent within 480 min at the optimal conditions of initial pH 3, CS/IONPs dosage 2.5 g/L, temperature 25 °C, and initial Cr(VI) concentration 150 mg/L. The co-existing cations didn’t affect Cr(VI) adsorption capacity of CS/IONPs beads, though PO43− and SO42− competed slightly with Cr(VI) adsorption. Cr(VI) removal process was spontaneous and exothermic and followed the pseudo-first-order kinetic. CS/IONPs composite beads could adsorb a maximum of 345.53 mg Cr(VI) per g of IONPs as determined by Langmuir isotherm. The used CS/IONPs beads could be regenerated using NaOH for the initial 4 cycles, but about 15.7 % of active sites were reduced afterwards. Cr(VI) removal involves electrostatic interaction, Cr(VI) reduction to Cr(III), Cr(III) adsorption, Cr(III) surface complexation through abundant –NH2 group, and Cr(III) co-precipitation with Fe(III).

A Novel Chalcopyrite Depressant for Selective Separation of Molybdenite from Cu-Mo Sulfide Ores and Its Interaction Mechanisms

In this study, GX2 was applied as a new high-efficiency chalcopyrite depressant to selectively separate molybdenite from Cu-Mo sulfide ores. The flotation performance and its interaction mechanisms with chalcopyrite and molybdenite were investigated using single-mineral and artificial-mixed-ore flotation, contact angle measurements, zeta-potential measurements, infrared spectroscopy, and X-ray optoelectronic spectrum analysis. The results indicated that molybdenite could be selectively separated from chalcopyrite under the optimal flotation conditions of pH 9.0, 80 mg/L GX2, 20 mg/L kerosene, 10 mg/L MIBC, and a flotation time of 3 min, while the molybdenite and chalcopyrite recoveries were around 90% and 5%, respectively. It was confirmed that GX2 could save ten times the depressant dosage compared to that of the Na2S baseline to achieve a similar separation efficiency. The contact angle test, zeta potential, infrared spectrum, and XPS results show that GX2 may be adsorbed on the surface of chalcopyrite via chemical adsorption, and the hydrophilic substances formed change its hydrophobicity, whereas the effect on the floatability of molybdenite is small, resulting in the excellent separation efficiency of chalcopyrite and molybdenite via flotation.

Eosin Y embedded Gd-MOF as a dual emission detection platform for dopamine

A 2D Gd-MOF {Gd-MOF = [Gd(L)(NO3) (DMF)2]n (H2L = 2,5-Bis(1,2,4-triazol-1-yl) terephthalic acid, DMF = N, N-dimethylformamide)} was synthesized based on solvothermal method. To achieve double emission peaks, Eosin Y embedded Gd-MOF (EY@Gd-MOF) was prepared through the synthetic encapsulating method. Due to the effective FRET between EY and Gd-MOF, EY@Gd-MOF shows double emission characteristic peaks. The ratio of emission peaks is used as the detection signal to replace the absolute fluorescence intensity of emission peak, and EY@Gd-MOF as a self-calibrated fluorescence sensor to detect dopamine, which realizes the selective detection of dopamine. Under optimal conditions of pH = 9, dopamine polymerizes to produce polydopamine, which attaches to the surface of EY@Gd-MOF and completely quenches the fluorescence of EY@Gd-MOF and the detection limit for dopamine is 0.124 μM. Because the excitation spectrum of Gd-MOF fully covers the ultraviolet absorption spectrum of polydopamine, energy competitive absorption is the major cause of fluorescence quenching. In addition, EY@Gd-MOF can be made into a test strip to detect dopamine, and also has the ability to detect in synthetic urine, providing a feasible scheme for the actual detection of dopamine.

Green synthesized zinc oxide nanoparticles for removal of carbamazepine in water and soil systems

During the COVID-19 pandemic, there was a significant increase in pharmaceutical releases (4 %), which created a pressing global need for solutions. In this study, we explored the use of zinc oxide nanoparticles (GS-ZnONPs) derived from neem (Azadirachta indica) leaves for separating antiepileptic drug carbamazepine (CBZ) from wastewater. CBZ is a major emerging pollutant in wastewater that can be reused for various purposes, including food production and drinking water. The study found that the GS-ZnONPs were effective in removing CBZ from water, with an adsorption capacity of 27.55 mg g−1 at room temperature. The GS-ZnONPs, under optimal conditions of pH 5.0, 100 mg of adsorbent, and 12 mg L−1 of CBZ at 25 °C ± 2 °C, demonstrated a remarkable removal efficiency, successfully eliminating 92.89 % of CBZ from water. Additionally, the study found that CBZ binds strongly to GS-ZnONPs, making them effective for removing CBZ from soil as well. The results suggest that GS-ZnONPs synthesized from neem leaves could be a low-cost and sustainable solution for removing emerging pollutants from wastewater and soil. Future studies could investigate the adsorption mechanisms, functional groups, respective pH ranges, and reuse of these low-cost adsorbents to further optimize their efficiency in tackling emerging pollutants.

Sustainable waste utilization: Geopolymeric fly ash waste as an effective phenol adsorbent for environmental remediation

Rapid industrialization and urbanization generate significant waste, including fly ash, posing environmental challenges. Utilizing these materials is essential to mitigate impacts and promote sustainable development. This research paper focuses on the innovative application of geopolymeric fly ash (GEOFA) waste modified with titanium oxide (TiO2) (GEOFA-TiO2) as a promising adsorbent for the removal of phenol compounds from contaminated water. Analysis showed that the modification process resulted in the formation of functional groups such as -OH, which aided in the adsorption process. Adsorption studies were conducted to evaluate the influence of pH, temperature, and concentration on phenol removal. The maximum percentage removal of phenol was achieved at optimum conditions of pH 6 and a temperature of 25 °C, with an adsorption capacity of 166.7 mg/g. The adsorption process followed the Langmuir model, suggesting a monolayer adsorption mechanism and the thermodynamic studies revealed that the phenol adsorption onto GEOFA-TiO2 was an endothermic process with a promising affinity between phenol and the adsorbent. This study demonstrates the effective use of modified fly ash-based adsorbents to remove phenolic contaminants. By repurposing waste materials, this research addresses waste management challenges and promotes sustainable practices, reveling their potential for environmental remediation.

Screening of cadmium-chromium-tolerant strains and synergistic remediation of heavy metal-contaminated soil using king grass combined with highly efficient microbial strains

The present study involved the isolation of two cadmium (Cd) and chromium (Cr) resistant strains, identified as Staphylococcus cohnii L1-N1 and Bacillus cereus CKN12, from heavy metal contaminated soils. S. cohnii L1-N1 exhibited a reduction of 24.4 % in Cr6+ and an adsorption rate of 6.43 % for Cd over a period of 5 days. These results were achieved under optimal conditions of pH (7.0), temperature (35 °C), shaking speed (200 rpm), and inoculum volume (8 %). B. cereus strain CKN12 exhibited complete reduction of Cr6+ within a span of 48 h, while it demonstrated a 57.3 % adsorption capacity for Cd over a period of 120 h. These results were achieved under conditions of optimal pH (8.0), temperature (40 °C), shaking speed (150 rpm), and inoculum volume (2–3 %). Additionally, microcharacterization and ICP-MS analysis revealed that Cr and Cd were accumulated on the cell surface, whereas Cr6+ was mainly reduced extracellularly. Subsequently, a series of pot experiments were conducted to provide evidence that the inclusion of S. cohnii L1-N1 or B. cereus CKN12 into the system resulted in a notable enhancement in both the plant height and biomass of king grass. In particular, it was observed that the presence of S. cohnii L1-N1 or B. cereus CKN12 in king grass led to a significant reduction in the levels of Cd and Cr in the soils (36.0 % and 27.8 %, or 72.9 % and 47.4 %, respectively). Thus, the results of this study indicate that the combined use of two bacterial strains can effectively aid in the remediation of tropical soils contaminated with moderate to light levels of Cd and Cr.

Inhibitive determination of organophosphate pesticides using acetylcholinesterase and silver nanoparticle as colorimetric probe

Accurate and real-time detection of pesticides is needed to ensure food safety and ecosystem protection. A biosensor was developed to determine organophosphate pesticides using acetylcholinesterase (AChE) and silver nanoparticle (AgNP) immobilized on the alginate-chitosan film matrix. The sensing principle is based on organophosphate pesticides (OP) inhibiting AChE activity. AChE hydrolyzes acetylthiocoline (ATCh) to thiocholine (TCh) and acetic acid (AA). The -SH group on TCh induces AgNP aggregation, resulting in fading of the film's brownish-yellow color. The presence of OP in the sample inhibited AChE activity, leading to a decrease in TCh and color fading. The biosensor response is determined by measuring the Red Green Blue (RGB) value of the film. The biosensor offers rapid detection directly in-situ and real time without the use of sophisticated instruments, with optimal measurement conditions of pH 7, incubation time of 1 minute, and concentrations of AgNP, ATCh, and tris-HCl buffer of 10 μg/mL, 50, and 7 mM, respectively. Biosensors have excellent sensitivity, reproducibility, and selectivity. Measurement of OP levels in nine vegetable samples revealed that the proposed colorimetric probe's results agreed well with the GC result as the reference method. Therefore, this method can be applied in monitoring food and environment OP levels.