Insights into remediation technology for malachite green wastewater treatment

Malachite green (MG) dye is a common industrial dye and organic contaminant that can be found in (waste)water. Textile and food industries make use of MG as dyeing and food coloring agents, respectively. However, MG is both genotoxic and mutagenic. Hence, the elimination of MG from MG-laden-wastewater is germane. This review summarizes up-to-date researches that have been reported in literature as regards the decontamination of toxic MG wastewater. Various removal methods (adsorption, membrane, Fenton system, and heterogenous and homogeneous photodegradation) were discussed. Of the two basic technologies that are comprehensively explored and reviewed, chemical treatment methods are not as viable as physical removal methods, such as the adsorption technology, due to the lack of secondary pollutant production, simple design, low operation costs, and resource availability. This review also presents various practical knowledge gaps needed for large-scale applications of adsorptive removal methods for MG. It concludes by recommending further research on the techniques of cheap and simple decontamination of MG to get clean water.

Malachite Green Adsorption Using Carbon-Based and Non-Conventional Adsorbent Made from Biowaste and Biomass:A Review

Dyes are pervasive contaminants in wastewater,posing significant health risks to both humans and animals.Among the various methods employed for effective dye removal,adsorption has emerged as a highly promising approach due to its notable advantages,including high efficiency,cost-effectiveness,low energy consumption,and operational simplicity compared to alternative treatments.This comprehensive review focuses on investigating adsorbents derived from biowastes and biomass,specifically carbon-based and non-conventional adsorbents,for the removal of malachite green,a widely used dye known for its toxic and carcinogenic properties.Carbon-based adsorbents encompass two main types:activated carbon and biochar,while non-conventional adsorbents refer to powder sorbents without carbonaceous treatments.Extensive studies have reported remarkable findings,with achieved maximum removal percentages exceeding 98%and capacities reaching 250 mg/g.These results highlight the exceptional efficacy of the reviewed adsorbents in eliminating malachite green from wastewater.By exploring the potential of bio-based adsorbents,this review sheds light on sustainable and environmentally friendly solutions for mitigating dye pollution.

Degradation of malachite green dye by Tenacibaculum sp. HMG1isolated from Pacific deep-sea sediments

A deep-sea bacterium from the Pacific Ocean identified as Tenacibaculum sp. HMG1 was found to have strong malachite green（MG） degradation activity. The MG tolerance and decolorizing activities of strain HMG1 were confirmed by bacterial growth and high-performance liquid chromatography（HPLC） analyses. Strain HMG1 was capable of removing 98.8% of the MG in cultures within 12 h and was able to grow vigorously at 20 mg/L MG. A peroxidase gene detected in the genome of strain HMG1 was found to be involved in the MG biodegradation process. The corresponding recombinant peroxidase（r POD） demonstrated high degradative activity at 1 000 mg/L MG. Based on the common candidate intermediates, strain HMG1 was inferred to have one primary MG degradation pathway containing r POD. In addition, five other candidate intermediates of the r POD-MG degradative process were detected. The optimal conditions for MG degradation were determined and showed that strain HMG1 and the r POD enzyme could maintain high bioactivity at a low temperature（20℃）, variable p H values（6.0–9.0）, higher salinities（100 mmol/L） and other factors, such as multiple metal ions, H2O2 and EDTA.MG-tolerant strain Tenacibaculum sp. HMG1 and its peroxidase have prospective applications as environmental amendments for MG degradation during coastal remediation.

Fe Nanoparticles Synthesized by Pomegranate Leaves for Treatment of Malachite Green

A green and convenient pathway of preparing iron nanoparticles(FeNPs)with pomegranate leaf(PG)extract for highly effective removal of malachite green(MG)was proposed under ambient conditions.The materials were characterized by scanning electron microscope(SEM),X-ray energy-dispersive spectrometer(EDS),Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)techniques.The results show that their surfaces are capped and stabilized by PG extract with amorphous nature and without any detection of zero-valent iron.The size and surface valence state of FeNPs are the key factors that affect the MG removal efficiency.As the reagent volume ratio of PG extract to FeCl_(3) increases greater than 1,the cross-linked FeNPs become more obvious,having a homogeneous distribution with the size range from 30 to 40 nm,and show an increasing ratio ofFe(Ⅱ)/Fe(Ⅲ),which is in proportion to the degradation efficiency of MG,reaching higher than 95%in only 2 min by using 50 mg Fe/L FeNPs and 200 mg/L MG.

Reactive species in resin supported heterogeneous Fenton-like oxidation of Malachite green solution

During the oxidative degradation of nonbiodegradable Malachite green (MG) by means of H2O2 /FeIIIR (iron supported on ion-exchage resin) in a dynamic column,the binding energy of the Fe(2p3/2) region for XPS spectra was found to be different between the top layer and the bottom layer in this column. Based on the data from XPS spectra and DMPO-OH·signal by EPR spectra,it is shown that the formation of ferryl (IV) is the key step for the oxidation of MG. The ferryl (IV) species can oxidize MG,and its redox potential is about 0. 739 - 0. 803 V measured by cyclic voltammograms (CV) . The catalytic capability of ferryl (IV) species was also evaluated,and it is found that it can promote the decomposition of H2O2 more efficiently than ferric iron. The removal rate of MG mainly depends on the adsorption of catalyst. Both ferryl (IV) and HO·radicals are the reactive species in the system. The oxidation of HO·is only a small part of the overall removal rate. Based on the obtained results,a possible mechanism for a resin-supported Fenton-like oxidation reaction is proposed.

Persistence of malachite green and leucomalachite green in perch (Lateolabrax japonicus)

The persistence of malachite green (MG), and its metabolite leucomalachite green (LMG), in fish tissues is still unclear, leading to many trade disputes. In this research, we established and evaluated an HPLC method that could detect MG and LMG simultaneously, and then investigated the persistence of these two toxins in the tissues of juvenile perch (Lateolabrax japonicus) post sub-chronic MG exposure at 1.0 mg/L. Exposure lasted for 2 h everyday and was repeated six times. The perch were then placed in MG-free seawater for 100 d to eliminate the toxins. Results show that MG accumulated in the tissues, including the gills, liver, muscle, blood and viscera, and then was metabolized rapidly to LMG. The concentrations of these two toxins increased significantly with the accumulation process. In general, the highest concentrations of MG and LMG in all tissue exceeded 1 000 μg/kg, except for MG in the muscle. The order of accumulation levels (highest to lowest) of MG was gill>blood>liver>viscera>muscle, while that of LMG was liver>blood>gill>viscera>muscle. High levels of MG or LMG could persist for several hours but decreased rapidly during the elimination process. The concentration of LMG was much higher than that of MG during the experiment, especially in the gill, liver and blood. Therefore, the three tissues play important roles in toxin accumulation, biotransformation, and elimination. Although the MG and LMG concentrations in muscle were much lower than in other tissues, the content still exceeded the European minimum required performance limit (MRPL), even after 2 400 h (100 d) of elimination. This demonstrates that it is extremely difficult to eliminate MG and LMG from tissues of perch, and therefore use of these toxins is of concern to public health.

Development of a Fast ELISA for the Specific Detection of both Leucomalachite Green and Malachite Green

Malachite green(MG), a dye, is an antifungal agent that has been used to treat and prevent fish diseases. It is metabolized into reduced leucomalachite green forms(LMG) that may reside in fish muscles for a long period, thus being harmful to human health. The aim of this study was to develop a competitive and direct enzyme-linked immunosorbent assay(ELISA) to detect MG and LMG specifically. The monoclonal antibody(m Ab) to LMG was generated using a hybridoma technique. The obtained m Ab showed good cross-reactivity(CR) to malachite green(MG), but not to crystal violet(CV) and Brilliant Green(BG). The m Ab was used to develop a fast detecting ELISA of MG and LMG in fish. By introducing the conjugation LMG-HRP, the detection capability was 0.37 ng m L-1 for MG and LMG. The mean recovery from spiked grass carp tissues ranged from 76.2% to 82.9% and the coefficients of variation varied between 1.8% and 7.5%. The stable and efficient monoclonal cell line obtained is a sustainable source of sensitive and specific antibody to MG and LMG.

Adsorption Characteristics of Activated Carbon Derived from Scrap Tires for Malachite Green:Influence of Small Organics

The influence of small organics on the adsorption characteristics of activated carbon produced from industrial pyrolytic tire char(APTC)for malachite green(MG) was investigated by a batch method. Phenol was chosen as the representative of small organics. The effects of phenol on adsorption equilibrium, kinetics and thermodynamics were studied systematically. The results indicate that APTC is a potential adsorbent for MG. The presence of phenol decreases the adsorption capacity of APTC for MG, but improves the rate of adsorption, while the adsorption characteristics, such as equilibrium, kinetics and thermodynamics are not affected by phenol. The adsorption equilibrium data follow Langmuir isotherm and the kinetic data are well described by the pseudo-second-order kinetic model. The adsorption process follows intra-particle diffusion model and the adsorption rate is determined by more than one process. Thermodynamic study shows that the adsorption is an endothermic and spontaneous physisorption process.

Flow-injection spectrophotometric determination of vanadium with malachite green oxalate by bromate in acidic and micellar medium

A flow injection method is proposed for determining vanadium（V）. The method is based on its catalytic effect on the oxidation of malachite green oxalate by bromate. The reaction was monitored spectrophotometrically by measuring malachite green oxalate absorbance at λmax = 625 nm. The reagents and manifold variables, which have influences on the sensitivity, were investigated and the optimum conditions were established. The optimized conditions made it possible to determine vanadium in the ranges of 10-140 ng/mL with a detection limit of 5.2 ng/mL and a sample rate of 20 ± 5 samples/h.

Adsorption of Malachite Green from Aqueous Solutions onto Rice Husks: Kinetic and Equilibrium Studies

A study was done to evaluate the removal of a cationic dye from simulated waste water onto rice husks (RH). Spectroscopic methods such as FTIR and SEM/EDX were used for adsorbent characterization. Experimental dependency on solution pH, initial dye concentration, agitation speed, adsorbentparticle size, temperature of the solution and contact time was evaluated. The adsorption data was tested using both Langmuir and Freundlich isotherms. The data fitted well into Langmuir isotherm model with a monolayer adsorption capacity of 6.5 mg/g. Further, the separation factor (RL) value was less than unity indicating a favorable adsorption process. Adsorption kinetics was determined using pseudo-first-order, pseudo-second-order and intra-particle diffusion models. The results showed that the adsorption of malachite green onto rice husks followed pseudo-second-order model with a determination coefficient of 0.986. This work has revealed that rice husks have a great potential to sequester cationic dyes from aqueous solutions and therefore it can be utilized to clean contaminated effluents.

Extraordinary adsorption of acidic fuchsine and malachite green onto cheap nano-adsorbent derived from eggshell

Removal of dyestuffs such as Acidic Fuchsine(AF)and Malachite Green(MG)being present in many forms in industries is vital to protect water reservoirs from their catastrophic effects on the ecosystem.This study attempts to effectively eliminate these dyes using a low-cost and eco-friendly material.Eggshell,as a biocompatible by-product,was initially characterized,then some modifications were conducted,and its morphology and chemical structure were then examined through(Atomic force microscopy)AFM,(Fourier-Transform Infrared Spectroscopy)FTIR,(Energy-Dispersive X-ray Spectroscopy)EDS and(Brunauer–Emmett–Teller)BET analyses.They revealed that the modifications on raw material gave rise to a natural nano-adsorbent presenting porous medium appropriate for targeted adsorbate molecules with the average particle size and average pore diameter of 54 and^2 nm,respectively.Functional groups on the adsorbent surface were also of importance to assist the adsorption of AF and MG.The effect of contact time,adsorbent dose,solution p H and initial concentration was evaluated.Pseudo-second order model accurately correlated the experimental kinetic data for both dyes.Moreover,the participation of intra-particle diffusion along with film diffusion in controlling the process was suggested.Langmuir isotherm model fitted very well to the equilibrium data for both dyes and maximum monolayer adsorption capacity of AF and MG was accordingly calculated to be 5000 and 3333.33 mg·g-1 respectively.The inherent characteristics of eggshell make it a potential material to remove contaminants from wastewater in future applications.

TiO₂Nanoparticles for Removal of Malachite Green Dye from Waste Water

In this research, we present a simple and successful route for synthesis titania nanoparticles by controlled solgel progress. Chitosan as bio-template is involved in the progress of preparation to increase the surface area and manipulate defined particle and pore structure. The crystalline behavior and the nanostructure of the prepared nanoparticles were investigated using X-ray diffraction [XRD] and transmission electron microscope [TEM]. The crystalline results have pointed out the predominant existence of anatase phase that reveals the successful role of chitosan in stabilizing titania nanoparticles and preventing the growth of these particles into rutile phase. It is obvious to notice that a change in sample crystallography from anatase to completely amorphous nanoparticles upon adsorption of malachite green dye indicates a strong adsorption of this dye that destroys the crystalline feature of titania sample. TEM analysis reveals the existence of spherical nanoparticles with size about 25 nm. The adsorption isotherm indicates the adsorption capacity 6.3 mg.g-1 TiO2. The value of enthalpy change (ΔH°) for malachite green dye adsorption is 19 kJ/mol, which indicates that the removal process is endothermic. The adsorption process follows pseudo-second order rate equation and the negative values of standard free energy (ΔG°) suggest that the adsorption process is spontaneous.

Visible Light Photocatalytic Degradation of Methylene Blue and Malachite Green Dyes with CuWO₄-GO Nano Composite

Copper Tungstate-Graphene Oxide nano composites have been successfully applied as excellent catalysts for the photocatalytic degradation with Methylene blue and Malachite green dyes under visible light irradiation. A facile?solid state metathesis synthesis of copper tungstate (CuWO4) followed by ball milling and subsequent preparation of copper tungstate-graphene oxide?(CuWO4-GO) nano composite using a colloidal blending process and its application as a visible light photocatalyst for the degradation of Malachite green and Methylene blue dyes. The morphology and composition of copper tungstate (CuWO4) nano composite have been characterized using X-Ray Diffraction (XRD), UV-Visible Diffuse Reflectance Spectra (UV-DRS), Raman Spectra, Field Emission Scanning Electron Microscopy (FESEM)-EDS and UV Visible Spectroscopy. It shows a band gap value of 2.13 eV, an increase in range and intensity of light absorption and the reduction of electron-hole pair recombination in CuWO4 with the introducing of GO on to it.

Mn/Mg/Ce-FA基催化剂制备及印染废水处理研究

针对目前印染废水中存在大量的染料颗粒,对生态系统中水资源质量以及生态环境造成了严重影响。本研究采用共沉淀法制备了锰/镁/铈(Mn/Mg/Ce)-粉煤灰(FA)基催化剂,并研究了其在孔雀石绿(MG)和甲基紫(MV)染料降解过程中的性能和作用机理。利用XRD、FT-IR、SEM、EDS对催化剂的结构、形貌及组成进行了表征,研究了催化剂与染料溶液的接触时间、催化剂用量和染料溶液的pH值对催化剂降解率的影响。结果表明,Mn/Mg/Ce-FA基催化剂颗粒表面金属氧化物附着均匀、催化效果较好。当接触时间为40min、催化剂用量为12g/L、染料溶液pH值为8时,催化剂对MG的降解效果最好;当接触时间为20min、催化剂用量为15g/L、染料溶液pH值为6时,催化剂对MV的降解效果最好,降解率能达到95%以上。Mn/Mg/Ce-FA基催化剂是一种性能良好的染料降解催化剂,在印染废水及其他的工业染料应用回收领域,具有广阔应用前景。

Effect of Back Diffusion of Mg Dopants on Optoelectronic Properties of InGaN-Based Green Light-Emitting Diodes

The effect of back-diffusion of Mg dopants on optoelectronic characteristics of InGaN-based green light-emitting diodes （LEDs） is investigated. The LEDs with less Mg back-diffusion show blue shifts of longer wavelengths and larger wavelengths with the increasing current, which results from the Mg-dopant-related polarization screening. The LEDs show enhanced efficiency with the decreasing Mg back-diffusion in the lower current region. Light outputs follow the power law L α I^m, with smaller parameter m in the LEDs with less Mg back-diffusion, indicating a lower density of trap states. The trap-assisted tunneling current is also suppressed by reducing Mg- defect-related nonradiative centers in the active region. Furthermore, the forward current-voltage characteristics are improved.

Preparation of K-doped g-C_(3)N_(4) composite loaded on magnetic attapulgite and its degradation performance for malachite green

Visible-light-driven photocatalysis is a promising technology for the treatment of dye wastewater.In this work,a novel photocatalyst of K-doped g-C_(3)N_(4) loaded on magnetic attapulgite(ATP)(Kω-g-C_(3)N_(4)@ATP-Fe_(3)O_(4))with excellent visible light photocatalytic properties and stability were successfully prepared and characterized.The removal efficiency of Kω-g-C_(3)N_(4)@ATP-Fe_(3)O_(4) for malachite green(MG)was studied,and the degradation mechanism was analyzed and proposed.It was found that the K_(5)-g-C_(3)N_(4)@ATP-Fe_(3)O_(4) photocatalyst possessed excellent degradation efficiency of over 98.0%for the MG dye wastewater under optimal conditions.Moreover,the K_(5)-g-C_(3)N_(4)@ATP-Fe_(3)O_(4) materials possessed good recyclability with a removal rate over 82%after 4 cycles.Under visible light condition,the K_(5)-g-C_(3)N_(4)@ATP-Fe_(3)O_(4) photocatalyst produce radicals of·OH and O_(2)^(-)to degrade the MG dyes,which was supported by electron paramagnetic resonance(EPR)and radical trapping experiments.In addition,the LC-MS analysis interpreted the degradation pathways and intermediates of MG in the solution.The findings in this work indicate that the prepared photocatalytic material has excellent degradation efficiency for MG and can be applied in dye wastewater treatment.

ZIF-67/CS对阳离子染料孔雀石绿的吸附性能研究

针对传统吸附剂与水相分离困难的问题,设计并制备了一种环境友好、成本低廉的壳聚糖复合材料ZIF-67/CS。针对吸附剂对孔雀石绿(MG)污染物的吸附性能,考察了污染物浓度、接触时间、吸附剂用量、pH和离子强度对其吸附性能的影响。利用XRD、SEM、FT-IR、TG等对其结构、形貌及热稳定性进行了表征。结果表明,在吸附实验中,303.15 K时ZIF-67/CS对MG的吸附等温线符合Temkin等温吸附模型;吸附动力学拟合结果表明,ZIF-67/CS对MG的吸附行为符合拟二级吸附动力学模型;吸附热力学结果表明吸附过程是自发的、吸热的。ZIF-67/CS对MG的吸附是一个复杂的化学吸附过程,主要由速率决定。

用于高效去除水中孔雀石绿的三层结构磁性复合材料Fe_(3)O_(4)@聚丙烯酸@ZiF-8的制备

设计并合成了一种以磁性纳米粒子为核,聚合物为中间层,金属有机骨架材料为外层的三层结构磁性复合材料(Fe_(3)O_(4)@PAA@ZIF-8)。首先利用溶剂热法制备Fe_(3)O_(4)纳米粒子,然后通过蒸馏沉淀聚合法在Fe_(3)O_(4)纳米粒子表面包覆聚丙烯酸(PAA)层,最后通过原位沉积法在PAA外部包覆ZIF-8。在对Fe_(3)O_(4)@PAA@ZIF-8的组成和结构进行表征的基础上,深入研究其对孔雀石绿(MG)的吸附性能。透射电子显微镜(TEM)显示Fe_(3)O_(4)@PAA@ZIF-8具有明显的三层结构,Fe_(3)O_(4)的平均粒径为117nm,PAA层厚度约为17 nm,ZIF-8层的厚度约为14 nm。Fe_(3)O_(4)@PAA@ZIF-8对MG的吸附量随着p H的升高而增大,吸附过程符合准二阶动力学模型和Langmuir等温吸附模型。此外,Fe_(3)O_(4)@PAA@ZIF-8还表现出良好的重复利用性能,8次循环利用后对MG(500 mg·L^(-1))的最大吸附量仍可达982 mg·g^(-1)。

Mg掺杂TiO_2光催化降解孔雀绿染料的研究

采用溶胶-凝胶法制备的Mg掺杂TiO2光催化剂降解孔雀石绿(MG)染料废水,考察了MG初始浓度、催化剂加入量等因素对其降解的影响。结果表明,Mg的掺杂显著提高了TiO2光催化降解孔雀石绿的活性,当催化剂用量为1.0 g/L,经120 min紫外光照射后,可使30 mg/L孔雀石绿溶液降解率达到84%,同时讨论了光催化机制。