Malachite Green Oxalate Research Articles

Using zero nano-valent iron/thin film composite (ZNVI/TFC) membrane for brackish water desalination and purification

This study looked at the use of synthetic Zero Nano-valent Iron (ZNVI) particles in a unique interfacial polymerization technique on a polyamide thin film PA(TF) composite membrane for the treatment and desalination of brackish wastewater. Zero nano-valent iron (ZNVI) particles were created utilizing chemical reduction technique. ZNVI/PA(TF) NCs membrane is the outcome of advancing the PA(TF) membrane by combining with different concentration of ZNVI particles into the organic phase 1,3,5-benzenetricarbonyl trichloride (TMC). ZNVI/PA(TF) NCs membranes and ZNVI particles' surface properties were examined by the use of mechanical activity, contact angle, BET, FTIR, SEM, XRD, zeta potential, TEM analysis, and EDX studies. Using a variety of salt solutions, such as NaCl, Na2SO4, MgSO4, NaHCO3, CaSO4, CaCl2, and MgCl2, the ZNVI/PA(TF) NCs membrane performance towards salt rejection, flux (at varying pressure), anti-fouling activity, and ZNVI particles stability was assessed. This work investigated the removal efficiency of four dyes: methylene blue (MB), methyl orange (MO), Congo red (CR), and malachite green oxalate (MG). The water flux of the pristine PA(TF) membrane improved from 22 to 35 L/m2.h at 15 bar, indicating a 63% flux enhancement and the NaCl rejection was improved from 88.5 to 98.6%, indicating an 11.4% rejection improvement by incorporation of 0.3 wt.% of ZNVI particles into PA(TF) matrix. The ZNVI/PA(TF) NCs membrane's separation performances were evaluated using 5000 mg/L feed solutions of various salts at 15 bar. It was discovered that the water flux and salt rejection are, respectively, 33.4, 33, 32.7, 32, 31, 30 and 29 L/m2.h for CaSO4, MgSO4, Na2SO4, NaCl, CaCl2, MgCl2, and NaHCO3, and 97.4, 97, 96.5, 96, 94, 93.2, and 92.8%. It demonstrates that the flux recovery ratio (FRR) of the ZNVI/PA(TF) NCs membrane is greater than that of pristine PA(TF) (78%), coming in at 87%. High stability and fixing of the ZNVI particles on the modified membrane surface is indicated by the low overall ZNVI particles release rate over the course of the 10-day experiment.

Gelatin Assisted Cerium–Copper Sulfide Nanoparticles as Efficient Catalysts for the Photocatalytic Degradation of Malachite Green Oxalate Dye Under UV‐A Light

AbstractChemical, petroleum, and dyeing industries generate a wide variety of highly toxic organic wastes. The discharge of this wastewater into the river without treatment will spoil the entire aquatic system. The photocatalytic degradation of dyes/toxic chemicals is considered a favorable technology for industrial wastewater treatment. For this purpose, we have prepared an efficient nanocomposite material. The Gelatin assisted Cerium loaded CuS (Ge−Ce−CuS) nanocomposite was successfully synthesized by a simple hydrothermal method and characterized by BET, UV‐DRS, and PL measurements. The BET surface area of Ge−Ce−CuS (88.6 m2 g−1) is higher than bare CuS (66.0 m2 g‐1). DRS Confirms that the photo‐absorption of Ge−Ce−CuS nanocomposite significantly increases from the 570 nm range to the whole visible region. PL measurements confirm that the CuS loading suppresses electron‐hole recombination of Ge−Ce−CuS. The photocatalytic activity of Ge−Ce−CuS was investigated for the degradation of malachite green oxalate dye (MGO) in an aqueous solution using UV light. The influence of operational parameters such as the amount of photocatalyst, dye concentration, and initial pH on the photo mineralization of MGO dye has been analyzed and discussed. Slightly basic pH enhances the degradation. The mineralization of MGO dye has been confirmed by COD measurements. The intermediates formed during degradations were analyzed by GC‐MS, and a suitable degradation pathway was proposed. The catalyst is found to be reusable. The mechanism of degradation of MGO dye by Ge−Ce−CuS is also proposed.

Highly active ZnO/Fe3+-TiO2 photocatalysts for visible-light photodegradation application and its colour change behaviour by d-d transition

Highly active novel ZnO/Fe-TiO2 composite catalysts with p-n junction heterostructure have been fabricated by adding commercial ZnO and sol–gel derived Fe-TiO2 nano-powders controlled by grinding and drying. This work reported that doped Fe (III) with TiO2 form a p-type semiconductor and whereas ZnO is an n-type semiconductor. The slight variation of electronegativity between ZnO and TiO2 causes a strong rectifying action for the formation of an interface between ZnO and Fe-TiO2. The occurrence of red shift phenomenon in absorption spectrum of the samples suggest the outcome of d-d transition of Fe3+ (2T2g → 2A2g, 2T1g) and the charge transfer transition between interacting Fe3+ ions (Fe3+ + Fe3+ → Fe4+ + Fe2+). These Fe3+ 3d states in addition to oxygen vacancies and Ti3+ centers create band states, thereby favouring the electronic transition to these levels and resulting in narrowing of TiO2 band gap. A direct confirmation is the increase of Urbach energy with the lowering in the band gap of ZnO/Fe-TiO2.The crystal field splitting of d orbitals (5 degenerate orbitals) of Fe3+ and the approach of free ligand ions which split into two sets and Fe3+ ligand field transition is discussed schematically. The photocatalytic activities of these heterostructure photocatalysts were evaluated by degrading toxic cationic organic dyes such as Methylene Blue (MB) and Malachite Green Oxalate (MG) under visible light. The mechanism of photocatalysis has been recommended which is based on the relative band structure of the semiconductor and integrated heterostructure. The formation of a spike barrier in the CB at the interface gives rise to trap sites that capture the migration of charge carriers and occurs recombination of electron-hole pair at higher Fe(III) doping concentration. The dark adsorption property of the catalysts sample has been also studied.

A novel laccase from Trametes polyzona with high performance in the decolorization of textile dyes

Laccases are multicopper oxidases able to oxidize several phenolic compounds and find application in numerous industrial applications. Among laccase producers, white-rot fungi represent a valuable source of multiple isoforms and isoenzymes of these multicopper oxidases. Here we describe the identification, biochemical characterization, and application of laccase 2 from Trametes polyzona (TP-Lac2), a basidiomycete fungus emerged among others that have been screened by plate assay. This enzyme has an optimal temperature of 50 °C and in acidic conditions it is able to oxidize both phenolic and non-phenolic compounds. The ability of TP-Lac2 to decolorize textile dyes was tested in the presence of natural and synthetic mediators at 30 °C and 50 °C. Our results indicate that TP-Lac2 most efficiently decolorizes (decolorization rate > 75%) malachite green oxalate, orange G, amido black10B and bromocresol purple in the presence of acetosyringone and 2,2′-azinobis (3-ethylbenzthiazoline-6-sulfonate)—ABTS. Overall, the laccase mediator system consisting of TP-Lac2 and the natural mediator acetosyringone has potential as an environmentally friendly alternative for wastewater treatment in the textile industry.

Capillary action-driven surface-enhanced Raman spectroscopy (SERS) for the identification of phthalocyanine blue in modern paintings based on the BPG spot test.

A method for the extraction and accumulation of Ag nanoparticles utilizing capillary action through a piece of triangular-shaped cotton paper is reported. This method allowed the integration of SERS and the BPG spot test, which are typically employed for examining pigments on paper or in books. Malachite green oxalate was used as the model material for investigating the extent of enhancement when SERS was applied. The dynamic behavior of the Ag nanoparticles was also studied. When the cotton paper was pre-treated with malachite green oxalate, Ag nanoparticles could be extracted and accumulated on the triangular top, resulting in a dramatic SERS improvement. When malachite green oxalate (at a concentration of 10-6 M) was applied using this method, a dramatic analytical enhancement factor of approximately 3000% was obtained. Finally, the method developed in this study was successfully applied to the analysis of pigments in paintings from a university collection. The findings revealed that phthalocyanine blue was a popular pigment used in numerous paintings during the 1950s.

Effective removal of malachite green oxalate from aqueous solution using Newbouldia laevis husk/MWCNTs nanocomposite: equilibrium, kinetics, and thermodynamics

The discharge of colored effluent into water bodies is a big concern; hence, the current work was designed to fabricate a superior nanocomposite (NBM) using the Newbouldia laevis husk (NB) and functionalized multiwalled carbon nanotubes (f-MWCNTs) for the adsorption of malachite green oxalate (MGO). Brunauer–Emmett–Teller (BET) surface analysis was used to assess the specific surface area of NB (0.7699 m2 g−1) and NBM (94.006 m2 g−1). Fourier transform infrared spectroscopy (FTIR) was employed to determine the chemical moieties on the surface of the adsorbent. Field emission scanning electron microscopy (FESEM) and thermogravimetric analysis (TGA) were used to analyze the surface morphology and the thermal behavior of the adsorbents. Essential factors of the adsorption process were investigated, and it was revealed that pH 6.0, adsorbent dose of 0.05 g, contact time 80 min, concentration of 100 mg dm−3 and maximum adsorption capacity of 35.78 mg g−1 (NB) and 69.97 mg g−1 (NBM) were the optimal parameters. The NB and NBM adsorption processes followed a pseudo-first-order kinetic model. The exothermic and endothermic adsorptive processes were noticed to be the best descriptions of MGO elimination by NB and NBM, respectively. The uptake of MGO by NB and NBM was best described by models of Freundlich and Langmuir isotherms. Besides, NBM demonstrated uptake efficiency that is >80% after the fourth adsorption/desorption cycle. As a result, NBM has a wide range of possible uses in environmental remediation.

Cellulose- supported sulfated-magnetic biocomposite produced from hemp biomass: Effective removal of cationic dyes from aqueous solution

In present study, eco-friendly sulfated cellulose-magnetic biocomposite was successfully synthesized with a simple method from hemp biomass. ATR-FTIR was used to determine chemical changes, while FE-SEM-EDS, STEM, XRD, TG/DTA, and BET techniques were employed to identify changes in morphology, elemental composition, crystal structure, and thermal degradation. Moreover, the saturation magnetization and pHpzc values of the MSHB were also determined. The effectiveness of magnetic sulfated hemp biomass (MSHB) was tested in the removal of cationic dyes from wastewater, including methylene blue (MB), crystal violet (CV), and malachite green oxalate (MGO). The adsorption all three dyes to MSHB, the pseudo-second-order kinetic model and the Langmuir model were determined to be more appropriate, and was endothermic and spontaneous from thermodynamic parameters, too. The maximum MSHB adsorption capacities were found to be 457.6, 509.3, and 1300 mg/g for MB, CV, and MGO at 298 K. With increasing temperature, it also drastically increased in capacity. The outstanding property of the MSHB is that it shows high removal performance wide pH range, even after ten cycles its high removal efficiency is still over 96 % for all three dyes and almost unaffected from dense matrix medium. These results demonstrate that MSHB is remarkable adsorbent for removing cationic dyes.

In Situ Synthesis of Bi2S3/BiFeO3 Nanoflower Hybrid Photocatalyst for Enhanced Photocatalytic Degradation of Organic Pollutants.

Photocatalytic degradation of Malachite Green oxalate (MG) in a water body is of significant importance to our health protection, as it could cause various serious diseases. However the photocatalytic activity of most catalysts is still unsatisfactory, due to the poor reactive oxygen species production as a result of sluggish charge separation. Here, innovative nanoflower-shaped Bi2S3/BiFeO3 heterojunctions are prepared via a facile sol-gel method, exhibiting an enhanced reactive oxygen species generation, which leads to the excellent photocatalytic performance toward MG degradation. We verify that interfacing BiFeO3 with Bi2S3 could form a fine junction and offers a built-in field to speed up charge separation at the junction area; as a result, this shows much higher charge separation efficiency. By virtue of the aforementioned advantages, the as-prepared Bi2S3/BiFeO3 heterojunctions exhibit excellent photocatalytic performance toward MG degradation, where more than 99% of MG is removed within 2 h of photocatalysis. The innovative design of nanoflower-like Bi2S3/BiFeO3 heterojunctions may offer new viewpoints in designing highly efficient photocatalysts for environmentally related applications.

Hierarchical MnO2-ZnO functionalized SiO2 nanofibrous membranes with enhanced Fenton-like catalytic performance for dye removal

In this work, flexible and hierarchical structured MnO2-ZnO/SiO2 nanofibrous membranes (NFMs) as easily recyclable Fenton-like catalysts have been developed utilizing the combination of electrospinning and a hydrothermal growth method. By capitalizing the advantages of the high specific surface area and synergism effects of bimetallic oxides, the optimal membranes exhibited prominent catalytic activity in the degradation of malachite green oxalate (MGO). Specifically, within a mere 15 min at an initial pH, 98.1% of MGO was degraded, demonstrating a remarkable degradation rate of 0.2744 min−1. Free radical scavenging experiments and Electron Paramagnetic Resonance studies conclusively identified superoxide radical species (O2•–) as the main reactive species for the degradation of MGO. Furthermore, the resultant flexible membranes displayed excellent stability and could be effortlessly recycled after catalytic process, surpassing the performance of conventional powdery Fenton-like catalysts. Notably, the resultant membranes could be used for dynamic catalyst for MGO removal and could efficiently treat 418 mL MGO with a flux of 5650.5 L m−2 h−1. The successful fabrication of these MnO2-ZnO/SiO2 membranes paves the way for the development of more efficient and applicable Fenton-like catalytic materials for water treatments and offers more inspirations for innovative designs of fiber-based or membrane-based catalysts.

Adsorption of Malachite Green Oxalate Dye by CuCo<sub>2</sub>O<sub>4</sub>/MgO Spinel Oxide Nanocomposite

The current study involves a synthesis of a composite of copper oxide and cobalt oxide as a spinel oxide load over magnesium oxide. This synthesis of nanocomposite material was from nitrate salts of the corresponding metals by co-precipitation method, while it was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction techniques (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and the activity of these materials was estimated by appreciated adsorption of malachite green oxalate (MGO) dye from its aqueous solution. Adsorption isotherm was investigated using both Freundlich and Langmuir adsorption isotherms. While the results of the spectrophotometric studies showed that the composition of synthesized supported oxides at 450 °C was spinel type with nanoparticle size, and the optimum removal efficiency was around 98% for the adsorption of MGO dye over spinel nanocomposite surface achieved by using a dye concentration of 5 ppm, a mass of adsorbent surface of 5 mg, in terms of the adsorption model's isotherms the obtained results showed that the removal of MGO dye by the surface of this material was more fitted with the Freundlich models' adsorption.

A novel Ce-Ni@biochar nanocomposite withenhanced photocatalytic activity towards organicdyesdegradation: impact of process variables and water matrices.

The intent of this research work is to implement a biogenic, affordable, and highly effective Ce-Ni@biochar catalyst in order to study its photoactivity in the removal of crystal violet and malachite green oxalate. The catalyst was synthesized using liquid phase reduction method where cerium and nickel nanoparticles are embedded on the rice husk biochar for photocatalytic degradation of organic dyes in the presence of sunshine. Various characterization techniques were conducted on fabricated catalyst for adequate evaluation of the chemical composition as well as morphological and topographical properties of the formed compound. The nanoparticles embedded on biochar persuade increased charge separation that resulted in a substantial decrease in electron-hole recombination rate. The synergistic actions of the catalyst resulted in a high level of photocatalytic activity. The fabricated nanocatalyst showed excellent photoactivity that caused 96 and 99% degradation of crystal violet and malachite green oxalate, a growing industrial pollutant, within 35 and 25 min, respectively. A persuasive mechanism and kinetics are well presented. A series of investigations were done on other factors, such as contact duration, catalyst dosage, starting concentration, interfering ions, and pH, to know its degradation pursuance. The impacts of different water matrices were also investigated. The removal effectiveness of the synthesized catalyst persisted after five consecutive cycles. Marking the burgeoning industrial effluents as a result of rapid industrialization and also focusing on easy availability and low-cost source as well as high efficiency, reusability of the catalyst imparts its novelty and need of this research work.

Preparation of highly effective bio-adsorbent from hemp fiber for removal of malachite green oxalate (MGO)

Preparation of highly effective bio-adsorbent from hemp fiber for removal of malachite green oxalate (MGO)

Highly effective Fe-doped TiO2 nanoparticles for removal of toxic organic dyes under visible light illumination

This article addresses the synthesis of Fe3+ doped TiO2 nanoparticles with variations of molar concentrations of Fe3+ and their adequate use as potential photocatalysts for Photocatalysis applications. Synthesized photocatalysts were characterized thoroughly by different analytical techniques in terms of morphological, chemical, structural, crystalline, optical, electronic structure, surface area etc properties. The occurrence of red shift phenomenon of the energy band gap attributes to the transfer of charges and transition between the d electrons of dopant and conduction band (CB) or valence band (VB) of TiO2. The doping of Fe3+ ions generates more trap sites for charge carriers with the surface trap sites. Thorough experimental conclusions revealed that the Fe3+ ions necessarily regulate the catalytic property of TiO2 nanomaterial. The obtained total degradation efficiency rate of Methylene Blue (MB) was 93.3% in the presence of 0.1 M Fe3+ in the host material and for Malachite Green Oxalate the efficiency was 100% in the presence of 0.05 M and 0.1 M Fe3+in the host material. In both the cases the total visible light irradiation time was 90 min. The adsorption properties of the photocatalysts have been also performed in a dark for 90 min in the presence of MB dye. However, till now there are hardly reported photocatalysts which shows complete degradation of these toxic organic dyes by visible light driven photocatalysis. of potential values of valence and conduction band shows the production of active oxidizing species for hydrogen yield and the possible mechanism of the Schottky barrier has been proposed. A schematic diagram of visible light driven Photocatalysis has been pictured showing degradation activity of Fe3+-TiO2 catalysts sample.

Scale-up factors, kinetics, passivation and sludge analysis for electrochemical removal of malachite green oxalate dye

ABSTRACT A new approach has been proposed to predict the effectiveness of electrocoagulation (EC) process to treat synthetic dye solution containing malachite green oxalate or Basic Green-4 (BG 4). Process intensification was used to optimise the EC operational parameters. Constant current batch galvanostatic studies were carried out under a single-pair Al electrode system at spacing (0.3–2 cm), dipped area (12–31 cm2), current (0.1–0.5 A), time (0–70 min) and dye concentration (10–1000 mg/L). Maximum dye removal efficiency >96 was attained within 10 min of the EC process with dye concentrations ranging from 100 to 1000 mg/L at optimal parameters of 6.98 pH, 0.5 cm spacing, 8 cm dipped length and 17.86 mA/cm2 current density. The dye removal and functional groups were verified by Fourier transform infrared spectroscopy (FTIR) and UV/Vis measurements. The field emission scanning electron microscope (FESEM) results revealed that the sludge containing dye particles included more carbon and small amounts of Na and Cl. According to the atomic force microscopy (AFM) findings, there was evidence of polynuclear aluminium floc production and pitting corrosion. Furthermore, PI values of 0.769 to 1 and 0.328 to 0.443 show that the particles in both EC supernatants are linear polynuclear groups with varying sizes. A linear association with R2 of 0.96 was found in the kinetic analysis between the loading concentration (Ci) and the optimal removal time (ORT). Based on ORT estimates, operating costs (OC) were calculated, and for Ci >806.33 mg/L, EC was determined to be cost-effective.

Eco-Friendly Gelatin–Cerium–Copper Sulphide Nanoparticles for Enhanced Sunlight Photocatalytic Activity

Using a semiconductor catalyst with sunlight can make the photodegradation of pollutants an economically viable process since solar energy is an abundant natural energy source. Solar photocatalysis can provide clean and green eco-friendly technology for the analysis of industrial effluents. Photocatalytic deterioration of the aqueous solution of malachite green oxalate dye (MGO dye) was studied using gelatin–cerium–copper sulphide (Ge-Ce-CuS) nanoparticles under the sunlight source. The nanoparticles were synthesised by a hydrothermal process. The structural properties of the nanoparticles have been characterised by XRD, SEM, EDS, HR-TEM, and XPS. The effects of the initial concentration of dye, dosage of photocatalyst, reaction time, and pH on dye removal efficiency were studied. The mineralisation of MGO dye has been confirmed by chemical oxygen demand (COD) measurements. The reusability of the catalyst was proved. The antibacterial activity has been studied for the synthesised nanoparticles. The higher photocatalytic degradation efficiency of Ge-Ce-CuS is explained by its reduced electron-hole recombination and sunlight activity.

Immobilization of biogenic silver–copper nanoparticles over arylated biochar from sugarcane bagasse: Method and catalytic performance

There is an ever‐growing demand for biochar production and its chemical transformation into specialty materials. Herein, we suggest a versatile method to elaborate Ag/Cu nanoparticles, by phytochemical process, on aryl‐sulfonated sugarcane bagasse pulp‐derived biochar. A binary nanocomposite has been fabricated through a four‐step strategy. The raw substrate biochar was first prepared by a slow pyrolysis of the biomass at 500°C under N2:H2 95%:5% inert atmosphere. Thereafter, in situ arylation of the biochar surface has been performed to obtain SO3H‐Biochar. The loading of silver and copper ions on SO3H‐Biochar has been achieved via a wet impregnation using a hydroalcoholic medium. Finally, the natural extract obtained from sugarcane bagasse has been employed to ensure the reduction of the adsorbed metal ions and obtain SO3H‐Biochar@Ag/Cu. Interestingly, the structural analysis of SO3H‐Biochar@Ag/Cu and the study of the evolution of D to G band intensity and area ratios have revealed that the metal phase deposition has altered the SO3H‐Biochar surface properties. It finally provided a more graphitized nanocomposite compared with the bare biochar and the intermediate substrate (SO3H‐Biochar). Such a result suggests that the phytochemical reduction has catalyzed the substrate graphitization. The catalytic performance of SO3H‐Biochar@Ag/Cu has been investigated in the oxidative degradation of malachite green oxalate. A total mineralization of the dye has been registered, and the experimental data were found to give a best fitting to the pseudo‐first‐order model. The fitting was relatively good with a mineralization apparent constant rate equals to 65 10−3 min−1. It is worth mentioning that all experiments used a relatively low amount of the composite catalyst (2.5 mg). So to recap, this route takes advantage of the two phases of sugarcane bagasse to generate a robust biochar‐based catalyst, its solid phase to derive biochar substrate with particular properties, and its liquid extract to be used as natural reducing preparation.

A new type of calcium-rich biochars derived from spent mushroom substrates and their efficient adsorption properties for cationic dyes.

Adsorption is commonly accepted as a most promising strategy in dye wastewater treatment, and the widespread use of adsorption emphasizes the need to explore low-cost but excellent adsorbents. Herein, a low-cost adsorbent (calcium-rich biochar) was developed, which was directly pyrolyzed from spent mushroom substate without any modification. This study evaluated the potential application of two calcium-rich biochars (GSBC and LSBC) derived from spent substrates of Ganoderma lucidum and Lentinus edodes, respectively. The effects of pyrolysis temperature on the calcium-rich biochars characteristics and their adsorption mechanism for cationic dyes (Malachite Green oxalate (MG) and Safranine T (ST)) were studied systematically. The increase in pyrolysis temperature from 350 to 750 °C led to an increase in both biochar ash, Ca content, and specific surface area, which made high-temperature biochars (GS750 and LS750) the superior adsorbents for cationic dyes. Batch adsorption results showed LS750 was more efficient to adsorb dyes than GS750 attributed to its higher Ca content and larger specific surface area. According to the Langmuir model, LS750 had high adsorption capacities of 9,388.04 and 3,871.48 mg g−1 for Malachite green and ST, respectively. The adsorption mechanism of dye MG could be attributed to pore filling, hydrogen bonding, electrostatic interaction, ion exchange, and π-π stacking, while ST adsorption mainly involved pore filling, electrostatic interaction, ion exchange, and π-π stacking. Attributed to their excellent adsorption performance, cheap source, and good reusability, biochars obtained from SMSs were very promising in dyeing wastewater treatment.

Effective sorptive removal of five cationic dyes from aqueous solutions by using magnetic multi-walled carbon nanotubes

Abstract The excellent properties of micro-nano materials and structures have attracted extensive attention especially in wastewater treatment. Based on this, magnetic multi-walled carbon nanotubes (MMWCNTs) have been prepared and used for the sorptive removal of five typical cationic dyes from aqueous solutions in the present study. Effects of several operational and environmental factors were investigated carefully, including initial pH values, common ions, contact time and temperature. The kinetics processes were well fitted by the pseudo-second-order kinetic model. The maximum adsorption capacities on MMWCNTs at 298.15 K for malachite green oxalate, auramine O, neutral red, crystal violet and rhodamine B were 442.2, 295.2, 183.4, 165.3 and 143.0 mg g−1, respectively. Differences in the size, structure and properties of these dyes led to the difference of adsorption amounts. ΔG0 were all negative within the temperature range tested, which meant the adsorption processes were spontaneous in nature. Moreover, the adsorption processes of targeted dyes, except auramine O, were exothermic and entropy decreasing. The regeneration studies indicated that the MMWCNTs showed high reusability and removal efficiencies above 75% can be achieved after four consecutive cycles. For the adsorption mechanism, electrostatic interaction, hydrogen bonds, π-π interaction together with hydrophobic interaction could coexist during the adsorption process.

Selection and Application of ssDNA Aptamers for Fluorescence Biosensing Detection of Malachite Green.

Malachite green oxalate (MG) is a kind of veterinary drug, which is freely soluble in water and hazardous to aquatic products, resulting in food toxicity and human health problems. The demand for effective and sensitive detection of MG residues is increasing in food safety. In this work, three DNA aptamers MG-36-12/16/17 targeting MG with good affinity (Kd values were 169.78, 71.94, and 102.46 μM, respectively) were obtained by Capture-SELEX. Furthermore, MG-36-12, MG-76-16-6A, and MG-36-17 were found to perform sensitively and specifically to detect MG as a sensing probe in a FRET fluorescent aptasensor, where the FAM-labeled aptamer and GO were employed as efficient energy donor–acceptor pair. The linear range of this aptasensor using aptamer MG-36-12 was from 1.71 to 514.29 ng/mL and the LOD was as low as 0.79 ng/mL. Additionally, the fluorescent assay using aptamer MG-36-17 to detect MG exhibited a linear relationship from 1.71 to 857.14 ng/mL and a LOD of 2.13 ng/mL. Meanwhile, the aptasensor showed high specificity to MG with no cross-reactivity to other veterinary drugs and had a mean recovery of 81.54% to 100.96% in actual water samples from the aquatic product market.

Malachite Green, the hazardous materials that can bind to Apo-transferrin and change the iron transfer

Different groups of synthetic dyes might lead to environmental pollution. The binding affinity among hazardous materials with biomolecules necessitates a detailed understanding of their binding properties. Malachite Green might induce a change in the iron transfer by Apo-transferrin. Spectroscopic studies showed malachite green oxalate (MGO) could form the apo-transferrin-MGO complex and change the Accessible Surface Area (ASA) of the key amino acids for iron transfer. According to the ASA results the accessible surface area of Tyrosine, Aspartate, and Histidine of apo-transferrin significantly were changed, which can be considered as a convincing reason for changing the iron transfer. Moreover, based on the fluorescence data MGO could quench the fluorescence intensity of apo-transferrin in a static quenching mechanism. The experimental and Molecular Dynamic simulation results represented that the binding process led to micro environmental changes, around tryptophan residues and altered the tertiary structure of apo-transferrin. The Circular Dichroism (CD) spectra result represented a decrease in the amount of the α-Helix, as well as, increase in the β-sheet volumes of the apo-transferrin structure. Moreover, FTIR spectroscopy results showed a hypochromic shift in the peaks of amide I and II. Molecular docking and MD simulation confirmed all the computational findings.