Effects Of Different Reaction Conditions Research Articles

Novel sunlight-induced monochloramine activation system for efficient microcontaminant abatement

As an eco-friendly and sustainable energy, solar energy has great application potential in water treatment. Herein, simulated sunlight was for the first time utilized to activate monochloramine for the degradation of environmental organic microcontaminants. Various microcontaminants could be efficiently degraded in the simulated sunlight/monochloramine system. The average innate quantum yield of monochloramine over the wavelength range of simulated sunlight was determined to be 0.068 mol/Einstein. With the determined quantum yield, a kinetic model was established. Based on the good agreement between the simulated and measured photolysis and radical contributions to microcontaminant degradation, the major mechanism of monochloramine activation by simulated sunlight was proposed. Chlorine radical (Cl•) and hydroxyl radical (HO•) were major radicals responsible for microcontaminant degradation in the system. Moreover, the model facilitated a deep investigation into the effects of different reaction conditions (pH, monochloramine concentration, and water matrix components) on microcontaminant degradation and radical roles. The differences between simulated and measured data of microcontaminant degradation under all conditions were less than 10%, indicating the strong reliability of the model. The model could also make good prediction for microcontaminant degradation in the natural sunlight/monochloramine system. Furthermore, the formation of disinfection byproducts (DBPs) was evaluated at different oxidation time in simulated sunlight/monochloramine with and without post-chloramination treatment. In real waters, organic components showed more pronounced suppression on microcontaminant degradation efficiency than inorganic ions. This study provided a systematic investigation into the novel sunlight-induced monochloramine activation system for efficient microcontaminant degradation, and demonstrated the potential of the system in practical applications.

Recycling of LiCoO2 from the cathode of a waste lithium battery via reduction in a molten salt

A new method for recycling and resynthesizing a lithium battery cathode material was developed. A LiCl-KCl molten salt was used as a medium. The raw materials were LiOH·H2O obtained by membrane electrolysis and Co2O3 obtained by carbothermal reduction, and the high-performance cathode material LiCoO2 was synthesized by molten salt method, and then placed into a battery for recycling. The specific reaction process and reaction kinetics for the LiCoO2 synthesis were studied by TG-DSC thermal analyses. The effects of different reaction conditions on the structure and morphology of the LiCoO2 were studied by XRD and SEM. The battery performance of the LiCoO2 was characterized with electrochemical analyses. The activation energies of the three endothermic reactions occurring in the synthetic process were calculated with the Kissinger method and were 34.212 kJ·mol−1, 168.53925 kJ·mol−1 and 221.26181 kJ·mol−1. The experimental battery prepared from a LiCoO2 sample calcined at 720 °C for 7 h showed first charge–discharge specific capacities of 150 mAh/g and 147 mAh/g, and the coulombic efficiency was 98%. The discharge specific capacity after 50 charge and discharge cycles was still 129 mAh/g. The battery showed good charge and discharge performance after rate cycling.

Synergistic preparation and application in PCU of α-calcium sulfate hemihydrate whiskers from phosphogypsum and electrolytic manganese residue

The α-calcium sulfate hemihydrate whiskers (α-CSHWs) were first prepared using phosphogypsum (PG) and electrolytic manganese residue (EMR) as raw materials for coating urea, demonstrating excellent controlled-release properties. The effects of different reaction conditions on α-CSHWs, achieved by optimizing the reaction time, the concentrations of NH4+, Mn2+, and other factors, were discussed. Results showed that when the EMR content was 25 wt%, the reaction temperature was 100 °C, and the reaction time was 3 h, α-CSHWs with a length-to-diameter ratio of 39 were obtained. Through experiments and density functional theory (DFT), the mechanism of α-CSHWs preparation was elucidated. The results show that the addition of EMR reduces the content of impurity ions PO43− and F− in PG while introducing NH4+ and Mn2+. Interestingly, both NH4+ and Mn2+ can reduce the nucleation time of α-CSHWs, while PO43−, Mn2+, and F− are more likely to adsorb on the (0 0 6) crystal plane of α-CSHWs, NH4+ readily adsorbs on the (4 0 0) crystal plane. The controlled-release performance of modified α-CSHWs incorporated into polyurethane-coated urea (PCU) was investigated, and it was found that the addition of Mα significantly prolonged the nutrient release period, with the period extending up to 116 days for coatings of 5wt% and above. This work not only enhances the efficiency of PG and EMR utilization but also serves as a reference for the straightforward synthesis and application of α-CSHWs.

Graft Copolymerization of Acrylonitrile onto Banana Cellulose Fiber

The graft co-polymerization of acrylonitrile monomer (AN) onto banana cellulose fiber (BCF) was carried out using ceric ammonium nitrate (CAN)/oxalic acid (OA) as redox pair in the aqueous nitric acid medium at 90 ºC. The effect of different reaction conditions on the grafting has been studied by determining the grafting parameters, i.e. concentration of acrylonitrile, ceric ammonium nitrate, oxalic acid, nitric acid, reaction time and temperature were carefully optimized to achieve the highest rate of grafting polymerization (RG), highest percent grafting yield (%GY) and grafting efficiency (%GE). All the reagents enhanced the RG%, GY% and %GE, with an increase of concentration up to a certain extent and then found to decline, except for the concentration of nitric acid. The grafting parameters were also increased with time/duration and temperature. The water retention value (WRV) of the grafted co-polymer was also measured. Activation parameters such as energy of activation (Ea), enthalpy change (ΔH), entropy change (ΔS) and free energy change (ΔG) can also be reported by using the Arrhenius plot. The evidence of grafting can also be predicted by the FTIR spectral analysis, moreover, the organic reaction mechanism has been proposed.

C–C bond coupling differences between β-O-4 and 4-O-5 ether bonds over hydrophobic mesoporous Ru/MY-O catalysts: from lignin model compounds to polycyclic alkanes

MY zeolites with mesopores were prepared by hydrothermal method using functionalized SiO2 (F-SiO2) as a silica source, and hydrophobic bifunctional Ru/MY-O catalysts were obtained by deposition precipitation method and silylation treatment. This work aims at obtaining polycyclic alkane (PCA) based high-density hydrocarbon fuels (HDHFs). We focused on the catalytic hydroconversion (CHC) of 2-phenoxy-1-phenylethanol (PP-ol) and oxydibenzene (ODB), two typical lignin-related model compounds (LRMCs), over Ru/MY-O. The effects of different reaction conditions and catalysts on the product distribution in PP-ol and ODB were investigated. The partial hydrogenation of ODB was found to be a necessary step before achieving C-O ether bond cleavage and C-C bond coupling. The balance of metal/acidic sites is critical for maximizing PCA yields. Changes in the metal/acid ratio had a greater effect on PCA yield in PP-ol than in ODB. Poor stability of cycloalkyl cations and partial hydrogenation of ODB hinder the generation of C-C coupling products. The incorporation of mesopores and hydrophobic treatment were found to weaken the negative effects of C-C bond coupling products and water on the catalyst. The conversion of Ru3/MY-O was improved by nearly 10% compared to Ru3/Y in the fifth cycle reaction. This work provided a theoretical basis for the generation of HDHFs from lignin.

Application of Green Synthesized Silver Nanoparticles for Dye Wastewater Treatment

A facile one-pot synthesis of silver nanoparticles (AgNPs) was achieved using the ethanolic extract of Cavendish banana florets as source of reducing agents for the conversion of Ag+ to Ag. The appearance of surface plasmon resonance peak between 410–435 nm in the UV Vis spectra confirmed the formation of AgNPs. The effects of different reaction conditions on the size and concentration of AgNPs were evaluated. The optimum conditions identified were pH 7 at 80 °C. Transmission electron microscopy (TEM) revealed spherical AgNPs with a mean particle size of 13.55 nm. On the other hand, energy-dispersive X-ray (EDX) analysis confirmed the presence of silver (Ag) as the bulk element (87.25%). Other elements such as carbon (C) and oxygen (O) are attributed to the capping agents of AgNPs which agrees with the results in the Fourier-transform infrared spectroscopy (FTIR) analysis. The optimized AgNPs were used for dye degradation using methyl orange (MO) as the model dye under acidified conditions. The maximum MO dye degradation of 96.07% and 77.32% at pH 1.5 and 2 were achieved after 10 min and 1320 min, respectively. This highlights the potential use of green-synthesized AgNPs for dye wastewater treatment.

G‐C3N4 Coating Enhanced Cu@AC for Catalytic Wet Air Oxidation of Phenol under Mild Conditions

AbstractA Cu‐based supported catalyst with g‐C3N4 coating (Cu/g‐C3N4@AC) was prepared by facile in‐situ growth over activated carbon surface with urea and Cu(NO3)2, and the catalytic performance for wet air oxidation of phenolic wastewater was investigated. The effects of different reaction conditions (catalyst, temperature, pressure and pH) were examined. The results show that under the catalysis of Cu/g‐C3N4@AC phenol could be completely oxidized at 120 °C and 0.5 MPa O2 with COD removal of 92.6 % (from 4883 mg/L to 361 mg/L). TEM, BET, XRD, FTIR and XPS characterizations showed that g‐C3N4 coating could strengthen the metal surface interaction via the Cu−N−C bonds formation, thus suppressing the aggregation of the active components on the surface and mitigating the catalyst deactivation. Moreover, the interaction between the Cu species and the g‐C3N4 structure facilitates the electron transfer and thus significantly boost up the catalytic activity. These findings help explore efficient catalysts for the wastewater treatment via wet air oxidation under mild conditions.

Synthesis of Urea-Formaldehyde Fertilizers and Analysis of Factors Affecting These Processes

Urea formaldehyde slow-release fertilizers are efficient and environmentally friendly fertilizers. They have good slow-release properties and can significantly improve the utilization rate of fertilizers. However, problems remain regarding the synthesis of urea formaldehyde slow-release fertilizers, their characterization, and aspects of their performance. This study explores the effects of different reaction conditions on the quality of synthesized urea formaldehyde and establishes a response relationship between synthesis factors and sustained-release performance. Optimal conditions for urea formaldehyde synthesis included use of an ammonium chloride catalyst, pH 4 as the final pH condition, and a urea/formaldehyde molar ratio (U/F) of 1.3. Samples prepared in this study were characterized in terms of cold water-insoluble nitrogen, hot water-insoluble nitrogen, and soil-available nitrogen. The samples were also characterized by spectroscopic and instrumental methods to correlate the microscale behaviors of the urea formaldehyde particles with their performance as controlled-release fertilizers. This work is expected to provide a basis for the production of urea formaldehyde and to improve its performance as a slow-release fertilizer.

Preparation of vacuum-assisted conjugated linoleic acid phospholipids under nitrogen: Mechanism of acyl migration of lysophospholipids

Sn-Glycerol-3-phosphatidylcholine (GPC) was prepared by hydrolysis of phosphatidylcholine (PC) catalyzed by phospholipase A1 (PLA1). Nitrogen flow assisted the esterification of conjugated linoleic acid (CLA) and GPC to produce conjugated linoleic acid lysophosphatidylcholine (LPC − CLA). The effects of different reaction conditions on the PC conversion and acyl migration rates were investigated, and the acyl migration mechanism under acidic and alkaline conditions was studied. In addition, the optimum conditions for the esterification of CLA and GPC were selected. The optimal condition for the hydrolysis of PC was an enzyme loading of 5 %, pH of 5, reaction temperature of 50 ℃, and reaction time of 3 h. The results also showed that the maximum esterification rate reached 82.37 % at an enzyme loading of 15 %, CLA/GPC molar ratio of 50:1, and vacuum pressure of 13.3 kPa. This study not only improved the bioavailability of PC but also effectively increased the content of LPC − CLA.

Design of sisal fibre biochar/poly(dopamine)/NZVI@PAN membrane for efficient degradation of tetracycline

A modified membrane-loaded iron composite PDA/PAN/BC-Fe0 (PPBN) was successfully prepared using sisal fibre biochar (SF-BC) and poly(dopamine) (PDA) functionalized modified hydrophilic porous polyacrylonitrile (PAN) membranes and used to support nano zero-valent iron (NZVI) for the first time. The effect of different reaction conditions and interfering factors on the degradation performance for the removal of tetracycline (TC) was investigated. In addition, the cycling and stability performance of PPBN was assessed. The agglomeration and release of NZVI particles were effectively inhibited, and the reactivity and stability of PPBN were enhanced. The results showed that under the same reaction conditions, the removal efficiency of PPBN for TC could reach 90.16% in 120 min and has increased by 36.16% compared with NZVI. After 6 regeneration cycles, the removal efficiency of TC by PPBN only decreased by 10.22%. The reaction kinetic process conformed to the two-parameter pseudo-first-order kinetic model, and three degradation pathways for TC removal were proposed. The removal mechanism included the synergistic action of physical adsorption, chemical oxidation and reduction, and the key role was played by redox reactions induced by hydroxyl radicals (∙OH) and superoxide radicals (∙O2−). The results of the study provide a simple, efficient and stable material for the treatment of antibiotic wastewater.

Study on sustained-release polycarboxylate superplasticizer prepared by EPEG macromonomer

Ethylene glycol monomer polyoxyethylene ether (EPEG) is a new macromonomer that has been introduced in recent years. Its special molecular structure enables it to form copolymers with acrylic acid (AA) that are closer to the ideal copolymerization structure. However, the current production capacity is relatively small, so there are not many related studies. Therefore, this paper uses EPEG as the main raw material to prepare a slow-release polycarboxylate superplasticizer SP-YH. By studying the effects of different reaction conditions on the properties of SP-YH, the optimum synthesis conditions were determined. The structure of the polymer was characterized by gel permeation chromatography (GPC) and infrared spectroscopy (FTIR). In addition, the concrete test and hydration heat test results show that it has better slump protection performance and compression resistance than the commercial slump protection polycarboxylic acid water reducer.

Desulfurization Characteristics of Carbide Slag during Circulating Fluidized Bed Coal Combustion

At low loads, the desulfurization efficiency of circulating fluidized bed (CFB) boilers tends to decrease due to the deviation of low bed temperature from the optimal temperature required for limestone desulfurization. However, carbide slag, a waste product rich in Ca(OH)2 and possessing a low decomposition temperature, can be an economically viable alternative to limestone. In this study, the desulfurization characteristics during coal combustion with carbide slag addition were studied both in a fixed-bed reactor and a 30 kW CFB reactor. The effect of different reaction conditions on the desulfurization performance was evaluated. Results showed that the addition of carbide slag decreased SO2 emission effectively. A higher oxygen content prompted the improvement of the desulfurization efficiency. The carbide slag showed the highest desulfurization efficiency at about 800 °C. The desulfurization performance deteriorated when the temperature was beyond 800 °C. To explain this phenomenon, the micromorphology of carbide slag raw particle, calcined particle, and sulfated particle was observed by scanning electron microscopy. More holes formed on the surface of the particles after calcination. Besides, the outer surface of the holes formed more crystal grains with the increasing temperature. CaSO4 products covered the outer surface of the crystal grains after desulfurization. The crystal grain gaps on the surface of carbide slag were easily blocked at high temperatures, which resulted in the low desulfurization efficiency.

Evaluation the selectivity of three lipases in the synthesis of 1-oleoyl-2-palmitoyl-3-linoleoylglycerol, an asymmetric triacylglycerol

1-Oleoyl-2-palmitoyl-3-linoleoylglycerol (OPL) is the most abundant triacylglycerol (TAG) molecule in Chinese human milk. The selectivity of three lipases including Rhizomucor miehei lipase (RML), Thermomyces lanuginose lipase (TL), and Candida antarctica lipase (CALB) in OPL synthesis were evaluated. The effects of different reaction conditions on selectivity were first investigated. Unexpectedly, the three sn-1,3 regioselectivity lipases, also have selectivity for the structure of product TAGs. Compared with symmetric TAGs, lipases had poor selectivity toward asymmetric OPL. Furthermore, molecular simulations were used to deeply understand the molecular factors affecting lipase selectivity. The results showed that hydrophobic interactions, lipases lid domain flexibility, and the stability of hydrogen bonds between lipases and TAGs were the main molecular factors responsible for the selectivity of lipases.

Starfish-like particles and nanowires interwoven architecture of CuO for water infiltration–induced electrical device

In the face of sustainable energy development, electricity generation using liquid infiltration in small-sized channels has become one of the effective strategies to optimize energy utilization. As p-type semiconductors, CuO nanomaterials exhibit great potential in energy storage and conversion, which can be used as suitable active materials for constructing nanogenerators. In this study, we proposed CuO water infiltration–induced electrical devices based on starfish-like particles and nanowires (NWs) interwoven architecture. Attributed to the ionovoltaic effect, the electrical signal value is reflected by the difference in carrier concentration between wet and dry regions. Notably, we innovatively used the oxidation–reduction–reoxidation method to control the crystal structure of CuO. In addition, we examined the relationship between CuO microstructure and performance and further explored the effect of different reaction conditions on the device output performance. It was demonstrated that a single device (7.5 cm × 2.5 cm × 18.3 µm) can generate an open-circuit voltage (Voc) of 0.67 V and a short-circuit current (Isc) of 2.49 μA at room temperature when 30 μL of 0.1 mol L−1 NaCl solution permeates from one end of the film. Under a 0.5 mol L−1 NaCl condition (seawater concentration), the device can generate a Voc of 0.82 V and an Isc of 2.70 μA, which is expected to be utilized in the field of sensors for identifying the different concentrations of ions.

Preparation and Characterization of a Novel Cassava Starch-Based Phosphorus Releasing Super-Absorbent Polymer, and Optimization of the Performance of Water Absorption and Phosphorus Release.

To prepare a novel cassava starch-based phosphorus releasing super-absorbent polymer (CST-PRP-SAP), the single factor and orthogonal experiment were applied to analyze the effects of different reaction conditions on the absorption and phosphorus release capacities of CST-PRP-SAP samples. The structural and morphological characteristics of the cassava starch (CST), powdered rock phosphate (PRP), cassava starch-based super-absorbent polymer (CST-SAP) and CST-PRP-SAP samples were all compared with various technologies, such as the Fourier transform infrared spectroscopy and X-ray diffraction pattern, etc. The results showed that the CST-PRP-SAP samples had good performances of water retention and phosphorus release which were synthesized, such as the reaction temperature, starch content, P2O5 content, crosslinking agent, initiator, neutralization degree, and acrylamide content, which were 60 °C, 20% w/w, 10% w/w, 0.02% w/w, 0.6% w/w, 70% w/w, and 15% w/w, respectively. The water absorbency of CST-PRP-SAP was almost larger than that of the CST-SAP sample with a P2O5 content of 5.0% and 7.5%, and they all gradually decreased after three consecutive water absorption cycles. The CST-PRP-SAP sample could maintain about 50% of the initial water content after 24 h, even at the temperature of 40 °C. The swelling process of CST-PRP-SAP conformed to the non-Fickian diffusion, which was determined by the diffusion of water molecules and the relaxation process of polymer chain segments. The cumulative phosphorus release amount and release rate of the CST-PRP-SAP samples were increased with the increasing PRP content and the decreasing neutralization degree. After a 216 h immersion, the cumulative phosphorus release amount and release rate of the CST-PRP-SAP samples with different PRP contents were increased by 17.4 and 3.7 times, respectively. The rough surface of the CST-PRP-SAP sample after swelling was beneficial to the performance of water absorption and phosphorus release. The crystallization degree of PRP in the CST-PRP-SAP system was decreased and most of the PRP existed in the form of physical filling, and the available phosphorus content was increased to a certain extent. It was concluded that the CST-PRP-SAP synthesized in this study has excellent properties of continuous water absorption and retention with functions of promotion and the slow-release phosphorus.

Performance and kinetics study of glycerol ketal synthesis from biomass‐based platform chemicals catalyzed by metal salts

AbstractBackgroundMethyl levulinate glycerol ketal (MLK) is a new kind of glycerol ketal with a wide range of applications. The efficient and green synthesis of MLK from biomass‐based platform chemicals including methyl levulinate (ML) and glycerol (GLY) catalyzed by cheap metal salts was investigated. Effects of different reaction conditions on the GLY conversion and the MLK yield were discussed, and the optimization and the kinetics of ketal preparation were further developed.ResultsThe reaction time, amount of catalyst and ML:GLY molar ratio were optimized based on Box–Behnken experimental design. The average MLK yield of 97.6% could be obtained under the optimum reaction conditions of ML:GLY molar ratio 4:3, vacuum degree 90 kPa, AlCl3 1.8 g, temperature 126 °C and reaction time 2 h, and the AlCl3 could be reused ten times without deactivation. On this basis, the kinetics studies showed that the ketal reaction conforms to the pseudo‐second‐order kinetics model, and the values of pre‐referential factor and activation energy were 1.824 × 104 mol·(g·h)−1 and 90.69 kJ mol−1. A reaction pathway for the ketalization reaction was proposed.ConclusionsThese results provide references for the scale‐up of MLK synthesis and the development of a new glycerol ketal. © 2023 Society of Chemical Industry (SCI).

Gum katira-silver nanoparticle-based bionanocomposite for the removal of methyl red dye.

The present study aimed to synthesize gum katira-silver nanoparticle-based bionanocomposite. Different characterization techniques were used to analyze the synthesized bionanocomposite, such as Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), thermo-gravimetric analysis (TGA), and transmission electronic microscopy (TEM). AgNPs were formed and were 6-20nm in size. Thermo-gravimetric analysis showed that synthesized nanocomposites are more thermally stable than gum katira. All the reaction conditions, such as time, temperature, pH, solvent, amount of nanoparticles, the concentration of the initiator, crosslinker, and monomer were optimized with respect to swelling. The results showed that the highest percentage swelling (Ps) of Gk-cl-poly(AA) was 796%, and 867% of AgNPs were imbibed by Gk-cl-poly(acrylic acid)-AgNPs. Synthesized bionanocomposite was used as an adsorbent material for the adsorption of methyl red (MR) dye. The effects of different reaction conditions were also optimized to attain maximum adsorption of MR dye. The maximum dye adsorption through Gk-cl-poly(AA)-AgNPs bionanocomposite was 95.7%. Diverse kinetic and isotherm models were used to study the adsorption data. The R 2 value was established as 0.987 and k2 was .02671. The greater R 2 value of second-order kinetics over first-order kinetics suggested that MR adsorption by nanocomposite is best explained by pseudo-second-order kinetics, indicating that dye adsorption occurred through chemisorption. The R 2 value was determined to be .9954. The correlation coefficient values of Gk-cl-poly(AA)-AgNPs were best fitted by the Freundlich adsorption isotherm. Overall, synthesized bionanocomposite is a proficient material for removing of MR dye from wastewater.

Application of O3/PMS Advanced Oxidation Technology in the Treatment of Organic Pollutants in Highly Concentrated Organic Wastewater: A Review

The ozone/peroxymonosulfate (O3/PMS) system has attracted widespread attention from researchers owing to its ability to produce hydroxyl radicals (•OH) and sulfate radicals (SO4•−) simultaneously. The existing research has shown that the O3/PMS system significantly degrades refinery trace organic compounds (TrOCs) in highly concentrated organic wastewater. However, there is still a lack of systematic understanding of the O3/PMS system, which has created a significant loophole in its application in the treatment of highly concentrated organic wastewater. Hence, this paper reviewed the specific degradation effect, toxicity change, reaction mechanism, various influencing factors and the cause of oxidation byproducts (OBPs) of various TrOCs when the O3/PMS system is applied to the degradation of highly concentrated organic wastewater. In addition, the effects of different reaction conditions on the O3/PMS system were comprehensively evaluated. Furthermore, given the limited understanding of the O3/PMS system in the degradation of TrOCs and the formation of OBPs, an outlook on potential future research was presented. Finally, this paper comprehensively evaluated the degradation of TrOCs in highly concentrated organic wastewater by the O3/PMS system, filling the gaps in scale research, operation cost, sustainability and overall feasibility.

BUCKWHEAT STARCH-MYRISTIC ACID COMPLEX FORMATION: EFFECT OF REACTION TEMPERATURE AND MYRISTIC ACID CONCENTRATION ON DIGESTIBILITY PROPERTIES

This study aimed to investigate the effect of different reaction conditions on the digestibility properties of buckwheat starch-myristic acid complex samples produced using different myristic acid concentrations and different reaction temperatures. Response Surface Methodology was used to investigate the effect of reaction temperature (60-90°C) and fatty acid concentrations (0.1-0.8 mmoL/g) on digestibility properties. Resistant starch (RS) contents of samples increased with an increase in reaction temperature. The reaction temperature affected the rapidly digestible starch (RDS) and slowly digestible starch (SDS) content of samples. The highest RS content (32.57%) was obtained using 0.45 mmoL/g myristic acid at 90°C. The F, p (<0.05), and R2 values indicated that the selected models were significant for the digestibility properties of samples. The complex formation of buckwheat starch with myristic acid seems promising to increase the RS content. Buckwheat appears to have the potential as an RS source, although the studies are quite new yet.

A Sensitive and Selective Colorimetric Method Based on the Acetylcholinesterase-like Activity of Zeolitic Imidazolate Framework-8 and Its Applications.

In this study, a simple colorimetric method was established to detect copper ion (Cu2+), sulfathiazole (ST), and glucose based on the acetylcholinesterase (AChE)-like activity of zeolitic imidazolate framework-8 (ZIF-8). The AChE-like activity of ZIF-8 can hydrolyze acetylthiocholine chloride (ATCh) to thiocholine (TCh), which will further react with 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) to generate 2-nitro-5-thiobenzoic acid (TNB) that has a maximum absorption peak at 405 nm. The effects of different reaction conditions (buffer pH, the volume of ZIF-8, reaction temperature and time, and ATCh concentration) were investigated. Under the optimized conditions, the value of the Michaelis-Menten constant (Km) is measured to be 0.83 mM, which shows a high affinity toward the substrate (ATCh). Meanwhile, the ZIF-8 has good storage stability, which can maintain more than 80.0% of its initial activity after 30 days of storage at room temperature, and the relative standard deviation (RSD) of batch-to-batch (n = 3) is 5.1%. The linear dependences are obtained based on the AChE-like activity of ZIF-8 for the detection of Cu2+, ST, and glucose in the ranges of 0.021-1.34 and 5.38-689.66 µM, 43.10-517.24 µM, and 0.0054-1.40 mM, respectively. The limit of detections (LODs) are calculated to be 20.00 nM, 9.25 µM, and 5.24 µM, respectively. Moreover, the sample spiked recoveries of Cu2+ in lake water, ST in milk, and glucose in strawberry samples were measured, and the results are in the range of 98.4-115.4% with the RSD (n = 3) lower than 3.3%. In addition, the method shows high selectivity in the real sample analysis.