Initial Malachite Green Concentration Research Articles

Synergistic degradation of refractory organic pollutant by underwater bubbling plasma combined with heterogeneous Fenton process

Excessive discharge of the refractory organic pollutants endangers the development of the society and economy, thus seeking an efficient wastewater abatement method is an urgent need. Herein, Iron (Ⅱ) sulfide (FeS) was employed as the heterogeneous catalyst and coupled with underwater bubbling plasma (UBP) for the elimination of the refractory organic pollutant, malachite green (MG). FeS catalyst was synthesized using the solvothermal method and subsequently characterized comprehensively, focusing on its microstructure, specific surface area, chemical bonds and elements valence states. The UBP system combined with FeS (UBP/FeS) exhibited the robust synergism with a maximum synergistic factor of 1.89. The MG degradation percentage and rate constant were up to 94.7% and 0.237 min−1 within 12 min. The parameter experiments revealed that FeS dosage, pulse frequency, initial MG concentration and solution conductivity of 150 mg/L, 56 Hz, 5 mg/L and 21.8 μS/cm, respective, were more conducive for MG elimination. The MG removal efficiency reached 86.2% after five consecutive applications of FeS. Reactive substances including ·OH, ·O2−, eaq, O3 and H2O2 were confirmed to contribute to MG elimination. Additionally, the conversion circle between ≡ Fe(Ⅱ) and ≡ Fe(Ⅲ) promoted the catalytic conversion of H2O2 and O3 into ∙OH. The comparison of UV–vis spectra and total organic carbon of MG solution before and after reaction revealed the superior degradation of MG in the UBP/FeS system. Hypotheses regarding to the decomposition pathways of MG were formulated based on the identified intermediates. The toxicity level of MG solution was lightened after reaction. The above results indicate that UBP/FeS has the advantages of quick degradation and high efficiency, representing a promising approach for refractory pollutants treatment.

Enhanced Removal of Malachite Green from Wastewater Using Nonthermal Plasma Gliding Arc Discharge Combined with Ferrate Oxidation

The rapid and complete removal of Malachite Green (MG) dye was effectively achieved by combining potassium ferrate (Fe(VI)) treatment with nonthermal plasma discharge in both deionized water (DIW) and tap water (TW). This study evaluated the decolorization and mineralization efficiencies under varying MG concentrations, Fe(VI) dosages, and pH levels, as well as the impact of radical scavengers on the process. Fe(VI) alone resulted in moderate decolorization (35.01%) and low mineralization (21.46%) at an MG concentration of 50mg/L in DIW. Plasma discharge alone achieved mineralization rates of 20.6% in TW and 24.16% in DIW. While complete decolorization was observed for all initial MG concentrations, it required significantly longer treatment times (>30min). However, the combination of Fe(VI) with plasma (Fe(VI)-Plasma) demonstrated significant synergistic effects, achieving total decolorization and high mineralization rates -up to 92.5% in DIW and 88.7% in TW for 20mg/L MG- at much shorter treatment times. Radical scavenger tests revealed that hydroxyl radicals (OH) were the primary oxidants in MG degradation, followed by superoxide radicals and electrons. These findings suggest that the combined Fe(VI)-Plasma technology is a promising and efficient solution for dye removal, reducing both chemical usage and treatment time.

The modified pomegranate peel as an economical and highly effective adsorbent for malachite green dye removal from wastewater

This research investigated the ability of acid-modified pomegranate peel to remove malachite green (MG) dye from aqueous solutions. Pomegranate peel, an abundant agricultural byproduct, was modified using hydrochloric acid to enhance its adsorption capacity. The effects of parameters like particle size, pH, initial MG concentration, contact time, temperature and adsorbent dosage on the dye removal efficiency were studied. Under optimized conditions of pH 8, 40 min contact time, 25°C temperature and 0.01 g/ml adsorbent dose with 5 mg/L MG solution, about 96.8 % dye removal was achieved. Kinetic data fitted well to the pseudo-second order model, indicating chemisorption with electrostatic interactions governing the adsorption. Equilibrium data were best described by the Temkin isotherm model, suggesting a heterogeneous binding energy distribution. Thermodynamic calculations revealed the exothermic and spontaneous nature of MG adsorption. FTIR analysis confirmed introduction of functional groups like carboxyl, amine and alkyl groups on the adsorbent surface after acid modification, enabling interactions with dye cations. SEM images displayed increased surface roughness and porosity for the modified biosorbent relative to the raw form. The acid-modified pomegranate peel proved to be an economical, eco-friendly and effective adsorbent for removing the hazardous cationic dye MG from wastewater. The findings support agricultural waste valorization for environmental remediation applications.

Hollow ZIF-8 nanomaterial prepared via core-shell etching exhibits exceptional adsorption performance for malachite green

Metal-organic frameworks (MOFs) have attracted widespread attention due to their distinctive structural attributes, such as expansive surface areas and the ease of chemical modification. These characteristics endow MOFs with a high degree of versatility, making them suitable for a broad array of applications. Core-shell MOF@MOF structures have emerged as a notable research area, offering a strategy to enhance MOF functionality by depositing one MOF layer over another. In this study, hollow ZIF-8 nanocomposites were successfully synthesized via the etching process of ZIF-67@ZIF-8 structures. It is noteworthy that the nanomaterial exhibits exceptional adsorption capacity, with a maximum adsorption capacity of 7746 mg/g for malachite green (MG), surpassing that of many previously reported adsorbents. Moreover, the recyclability of these nanocomposites is also excellent, demonstrating sustained effectiveness over five adsorption-desorption cycles. The study systematically investigated key factors that influence MG adsorption, such as the amount of adsorbent used and the initial concentration of MG. Additionally, a comprehensive analysis of adsorption kinetics was conducted to gain insights into the adsorption behavior of the nanocomposites. In conclusion, the hollow ZIF-8 nanomaterial prepared via core-shell etching offers a promising platform for the efficient removal of MG, meeting the urgent demand for high adsorption capacity of MG in water treatment.

Modeling competitive biosorption for methylene blue removal on rape straw powders using response surface methodology in a ternary dye aqueous solution

The improvement of biosorption efficiency for selective dye removal in a multi-dye aqueous system has become an increasingly significant research topic. However, the competitive effects of coexisting dyes and the target dye in such systems remain uncertain due to complex interactions between adsorbent and coexisting dyes. Therefore, in this research, response surface methodology (RSM) model was effectively employed to investigate the competitive effects of allura red (AR) and malachite green (MG) on methylene blue (MB) removal in a ternary dye aqueous system using three different parts of rape straw powders. In the current design of RSM, the initial concentrations of AR and MG dyes ranging from 0 mg·L−1 to 500 mg·L−1 were considered as influencing factors, while the removal rates of MB on adsorbents at an initial concentration of 500 mg·L−1 were established as response values. The RSM models exhibited high correlation coefficients with adjusted R 2 values of 0.9908 (pith core), 0.9870 (seedpods), and 0.9902 (shells), respectively, indicating a close fitted between predicted and actual values. The proposed models indicated that the perturbation effects of initial AR and MG concentrations were observed on the removal rates of MB by three types of rape straw powders in a ternary dye aqueous system, resulting in a decrease in MB removal rates, particularly at higher initial AR concentration due to stronger competitive effects compared to initial MG concentration. The structures of rape straw powders, including pith core, seedpods and shell, were analyzed using scanning eletron microscoe (SEM), energy dispersive spectroscopy (EDS), N2 physisorption isotherm, frourier transform infared spectroscopy (FTIR), Zeta potential classes and fluorescence spectrum before and after adsorption of MB in various dye aqueous systems. The characteristics of rape straw powders suggested that similar adsorption mechanisms, such as electrostatic attraction, pore diffusion, and group complex formation for MB, AR, and MG, respectively, occurred on the surfaces of adsorbents during their respective adsorption processes. This leads to significant competitive effects on the removal rates of MB in a ternary dye aqueous system, which are particularly influenced by initial AR concentrations as confirmed through fluorescence spectrum analysis.

A comparative study on the malachite green dye adsorption of chemically synthesized and green MgFe2O4 nanoparticles using gerbera floral waste extract.

The situation of discharging a large amount of dyes from the textile industries has caused many adverse effects on human health and the ecosystems. Emerging bio-nanomaterials represent a new trend in efficient dye removal in aqueous media. Herein, we mention that MgFe2O4 bioprepared using gerbera extract has been successfully used to adsorb malachite green (MG) in water. A comparison was made to determine the dye removal efficiency between biogenic MgFe2O4 (MFOB) and chemical MgFe2O4 (MFOC). The spherical MFOB material exhibited a large surface area of 85.0 m2 g-1 and high crystallinity. The obtained outcomes showed that the highest adsorption capacity of MG dye was 584.49 mg g-1 at a MFOB dose of 0.05 g L-1 and MG concentration of 10 mg L-1. Higher correlation coefficients in the Langmuir isotherm suggested monolayer adsorption of MG. The Box-Behnken design and response surface method were established to optimize MG removal percentage under the conditions, i.e., initial MG concentration (10-30 mg L-1), adsorbent dose (0.02-0.08 g L-1), and pH of dye solution (6-8). MFOB had good reusability with high removal efficiencies after three continuous cycles. Post reuse, this adsorbent still showed excellent stability through the verification of their structural properties in comparison with fresh MFOB, showing potential for practical applications.

Effective removal of malachite green from local dyeing wastewater using zinc-tungstate based materials

The frequent use of an industrial dye such as malachite green (MG) has caused major water body deterioration and is one of the most pressing global challenges, demanding effective treatment techniques. To solve these issues, a simplistic method was developed to synthesize zinc-tungstate (ZnWO4) nanoparticles and also dope the surface matrix of the ZnWO4 nanoparticles using nonmetals of boron (B), carbon (C), and nitrogen (N) at different ratios for enhanced MG removal from wastewater. The prepared nanomaterials were characterized by different methods for crystal structure composition, surface properties, surface morphology, microstructures, functional groups, and elemental oxidation states. The BET analysis revealed a mesoporous structure with surface areas of 30.740 m2/g for ZnWO4, 38.513 m2/g for ZnWO4@BCN, 37.368 m2/g for ZnWO4@BCN/B, 39.325 m2/g for ZnWO4@BCN/C, and 45.436 m2/g for ZnWO4@BCN/N nanocomposites. The best removal of MG was accomplished at pH (8), contact period (50 min), nanoadsorbent dose (0.8 g/L), initial MG concentration (20 mg/L), and temperature (303 K). The maximum adsorption capacities of ZnWO4 and ZnWO4@BCN/N towards MG were 218.645 and 251.758 mg/g, respectively. At equilibrium, the Freundlich isotherm and pseudo-second-order kinetic models were the best fits for the experimental data of MG adsorption on both nanoadsorbents. After eight cycles of adsorption and desorption, both ZnWO4 and ZnWO4@BCN/N were found to be good at removing MG, with efficiencies of 71.00 and 74.20%, respectively. Thermodynamic investigations further validated the spontaneity and endothermic nature of the adsorption process. All study findings confirm the nanoadsorbents exceptional capability and economic feasibility for removing MG dye.

Utilization of Synthesized Copper Ferrite/Calcium Alginate Nanocomposite for Adsorption and Photocatalytic Degradation of Malachite Green

In this article, the effectiveness of two different application methods (photocatalytic degradation and adsorption) onto the created solid nanomaterials for the removal of malachite green (MG) was investigated. Copper ferrite nanoparticles (CF) and copper ferrite/calcium alginate composite (CG) were synthesized as two studied solid samples. By using XRD, TGA, FTIR, DRS, nitrogen adsorption/desorption isotherm, pHPZC, SEM, and TEM, the physicochemical and morphological properties of the solid samples were tested. Sample dose, pH, initial MG concentration, shaking time, ionic strength, UV light power, and temperature were the key experimental parameters that were established. The obtained results demonstrated that at 40 °C, CG reached a greater adsorption capacity (297.62 mg/g). The spontaneous, endothermic, and advantageous adsorption process of MG was proved by the best fitting of pseudo-second order, Elovich, intra-particle diffusion, Langmuir, Dubinin-Radushkevich, and Temkin models onto all the produced materials. The maximum percentage of MG degradation by CG (89.9%) was accomplished by utilizing 1.0 g/L of catalyst mass, an initial MG concentration of 10 mg/L, and 33 W. Arrhenius and Eyring–Polanyi models well applied the MG photodegradation onto the catalyst surface.

Fabrication of titania/calcium alginate nanocomposite matrix for efficient adsorption and photocatalytic degradation of malachite green

This work aims to examine the two techniques' efficiency for the elimination of malachite green (MG) by photocatalytic degradation and adsorption onto synthesized solid nanomaterials. Three solid samples were prepared as calcium alginate (AG), nanotitania (NT), and nanotitania/calcium alginate composite (TG). The morphological and physicochemical characteristics of the solid nanomaterials were investigated by XRD, TGA, DRS, FTIR, pHPZC, nitrogen adsorption/desorption isotherm, SEM, and TEM. The main experimental conditions were determined for sample dose, shaking time, pH, initial malachite green concentration, temperature, ionic strength, and UV lamp power. The resulting data proved that TG attained the higher adsorption capacity (252.52 mg/g) at 40 °C. The adsorption of MG was well fitted by Langmuir, Temkin, Dubinin-Radushkevich, pseudo-second order, intra-particle diffusion, and Elovich models onto all the prepared samples, confirming the endothermic, spontaneous, and favorable adsorption process. The maximum degradation percent (99.6 %) of MG was achieved by using 1.0 g/L as a catalyst dose, 10 mg/L of initial MG concentration, and 33 W for TG. The photodegradation of MG was well fitted by Eyring–Polanyi and Arrhenius models onto the surface of catalyst. The TG reusability resulted in a decrease in the degradation efficiency by 9.8 %, indicating its great capacity as the first nanotitania/calcium alginate nanocomposite used in removing MG from wastewater by two technologies in the same article.

Adsorption of malachite green from aqueous phase by tea stalk powder: Parameters, kinetic, isothermal, and thermodynamic studies

Decolorization of malachite green (MG) from the aqueous phase was investigated using tea stalk powder. The adsorption efficiency decreased with the initial MG concentration, ionic strength of the solution, and heavy metal content. A suitable initial MG concentration of up to 200 mg/L can be accepted because adsorption efficiency of more than 95% is achieved. Various adsorption kinetic models were used to fit the experimental data, and the data obtained was best explained by the pseudo second-order model. The adsorption capacities calculated with the pseudo second-order model at different initial MG concentrations ranging from 24.27 to 158.7 mg/g were very close to the experimental data. The Langmuir isotherm fitted well, and the thermodynamic investigation showed that the adsorption of MG by tea stalk powder was feasible, endothermic, and spontaneous. The regeneration/adsorption experiments indicated that the tea stalk powder remained more than 95% of efficiency after six cycles using NaOH as desorbent and thus could be used many times. In conclusion, tea stalk has considerable potential as a cost-effective adsorbent for the removal of MG.

Nonlinear kinetic modeling of malachite green adsorption onto green waste bio-adsorbents using CCF- RSM

Malachite Green (MG) adsorption by four different bio-adsorbents: Populus Nigra (PN), Pinus Strobus (PS), Fraxinus Excelsior (FE), and Phragmites Australis (PA) have been investigated. Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) analyses were conducted to identify the bio-adsorbents' characterization and study their adsorptive properties. The impact of essential factors, such as adsorbent dosage, initial solution pH, initial MG concentration, and interaction of factors were studied on removal efficiency by face centered design (CCF) as a feature of response surface methodology (RSM). Nonlinear kinetic models including pseudo-first, and pseudo-second order, Elovich, film diffusion, and intra-particle diffusion were evaluated using error functions in order to find the best fitted model. Comparing the obtained results revealed that PA is more effective in decolorization and has an uptake of about 90% in the optimum operating condition. For further investigation, its ashes have been used for MG removal, and as a result, 99.3% dye uptake by PA ash was obtained.

Design and development of a high-performance 3D graphene system for adsorptive removal of organic toxins from wastewater: Mechanisms and process optimization

Degradation of water quality caused by organic dyes discharge is a great concern owing to their high toxicity and bioaccumulative nature. A new three-dimensional cellulose/titanium/graphene oxide (3D-CTG) system was fabricated via an ecofriendly ice-segregation method for sequestrating malachite green (MG) and crystal violet (CV) dyes in polluted water. The designed graphene oxide-based system was validated by several analytical techniques, with the results indicating the formation of lamellar porous networks and abundant chemical functional groups. The adsorption of the dyes was modeled by response surface methodology whereby 4 parameters (dosage, initial concentration, temperature and contact time) were optimized to achieve the highest CV removal (94.29%) at 10 mg of adsorbent dosage, 70 mg/L of initial CV concentration, 30 °C and 45 min, and the highest MG removal (81.07%) at 12.5 mg of dosage, 40 mg/L of initial MG concentration, 40 °C and 31 min. The saturated 3D-CTG adsorbent was recyclable as supported by 41.1 – 71.7% regeneration efficiencies after the fourth cycle of usage. The Langmuir maximum adsorption capacities of CV (583.6 mg/g) and MG (334.8 mg/g) dyes were comparable to the literature data which reflected the superior adsorption performance and high applicability of the new 3D-CTG system in the decontamination of organic dyes wastewater.

Valorization of microwave-assisted H3PO4-activated plantain (Musa paradisiacal L) leaf biochar for malachite green sequestration: models and mechanism of adsorption

Utilization of synthetic dyes in different sectors has been identified as one of the major sources of environmental degradation; as a result, removal of their remnants from the industrial effluent is highly encouraged for conserving our environment. In this study, the synthesized plantain leaf biochar (PLB) was used for adsorbing synthetic malachite green (MG). The synthesized PLB was characterized through pHpzc, BET, XRD, SEM and FTIR spectrometry. The sequestration of MG onto PLB confirmed by FTIR and SEM was optimized by varying the adsorption parameters. The BET surface area (986.35 m2/g) and average pore diameter (44.13 Å) showcased PLB as an efficient mesoporous biochar capable of adsorbing MG (>99%) at optimum conditions of pH (8.0), initial MG concentration (50 mg/L), adsorbent dosage (0.2 g/L), contact time (80 min) and temperature of 301 K. Redlich-Peterson and Avrami fractional model best fitted the adsorption isotherm and kinetic model, respectively. ΔGo and ΔHo being negative confirmed the feasibility and exothermic nature of the adsorption process. The outstanding regeneration (>97%) of PLB after the fifth regeneration cycle established PLB as a potential sustainable green adsorbent for future industrial wastewater treatment.

Contribution of zeolite to remove malachite green in aqueous solution by adsorption processes: Kinetics, isotherms and thermodynamic studies

The textile industry produces huge amounts of wastewaters containing synthetic dyes. In the textile industry, acid, basic, reactive, dispersed chemicals are widely used for dyeing. The aim of this study was to evaluate the adsorption of malachite green onto zeolite from aqueous solutions was realized in batch system. The adsorbent was characterized by the Fourier transform infrared spectroscopy, X-ray analysis, and zero point charge (pHzpc = 10.42). However, some examined factors were found to have significant impacts on the adsorption capacity of zeolite such as the initial malachite green concentration (Co), solution pH, adsorbent dose, agitation speed, particles size, and temperature. The best capacity was found at pH 8 with an adsorbent dose 0.2 g/l, an agitation speed 200 rpm and a contact time of 40 min. The kinetic adsorptions were found to follow rather a pseudo-second order kinetic model with a determination coefficient (R2) of 0.999. The equilibrium adsorption data for the malachite green adsorption onto the zeolite were analyzed by the Langmuir, Freundlich, Elovich, and Temkin models. The results indicate that the Langmuir model provides the best correlation with a capacity qmax of 83.33 mg/g at 25°C. The adsorption isotherms at different temperatures have been used for the determination of thermodynamic parameters, namely the free energy (ΔG°); enthalpy (ΔH°) and entropy (ΔS°) to predict the nature of adsorption. The positive values of ΔG° and ΔH° indicate that the overall adsorption is not spontaneous and endothermic with a physisorption process. The adsorbent elaborated from the zeolite was found to be efficient and suitable for the elimination of reactive dyes from aqueous solutions, due to its availability of adsorption sites, low cost preparation, and good uptake capacity.

Preparation and characterization of low-cost adsorbents for the efficient removal of malachite green using response surface modeling and reusability studies

Malachite green used in textile and dyeing industries is a common persistent pollutant in wastewater and the environment causing major hazards to human health and aquatic organisms. In this study, the response surface methodology was applied to optimize the adsorptive removal of malachite green using nano-bentonite, MgO-impregnated clay, and Mucor sp. composites. The nano materials and Mucor sp. composite were characterized by FTIR, SEM and X-ray diffractometry. According to the obtained results, nano-bentonite exhibits a maximum MG adsorption efficiency of 98.6% at 35 °C, pH 7.0, 60 min contact time, 1.0 g/L adsorbent dosage, and 50 mg/L initial MG concentration. On the other hand, the maximum efficiency for MG adsorption on MgO-impregnated clay of 97.04% is observed at pH 9.0, 60 min contact time, 0.7 g/L adsorbent dosage, and 50 mg/L initial MG concentration. The Malachite green (MG) adsorption isotherm on MgO-impregnated clay corresponded with the Freundlich isotherm, with a correlation coefficient (R2) of 0.982. However, the Langmuir adsorption isotherm was a superior fit for nano-bentonite (R2 = 0.992). The adsorption activities of nano-bentonite and MgO-impregnated clay were fitted into a pseudo-second-order kinetic model with R2 of 0.996 and 0.995, respectively. Additionally, despite being recycled numerous times, the adsorbent maintained its high structural stability and removal effectiveness for nano-bentonite (94.5–86%) and MgO-impregnated clay (92–83%).

Optimization of the Fabrication of Sustainable Ceramsite Adsorbent from Coal Fly Ash/Waterworks Sludge/Waste Glass for Decolorization of Malachite Green

As a traditional dye, malachite green (MG) poses a threat to our environment and health. To decolorize MG, a composite ceramsite adsorbent composed of coal fly ash (CFA), sewage treatment sludge (STS), and waste glass (WG) with a quality ratio of 3 : 3 : 4, respectively, was prepared. The optimal preparation parameters were determined as follows: preheating [Formula: see text], sintering [Formula: see text], and sintering [Formula: see text]. Under optimal conditions, scanning electron microscopy (SEM) images show that the X-Com-ceramsite sample exhibits rough features and a porous structure. The obtained X-Com-ceramsite has a good MG decolorization effect (92% decolorization rate with an initial MG concentration of 56.876 mg/L). The [Formula: see text] value of MG can reach up to 37.6 mg/g. The retention degree of MG in the X-Com-ceramsite with a relatively higher pH is stronger, and the adsorption process is spontaneous and endothermic. Synchronous fluorescence, two-dimensional correlation spectroscopy (2D-COS), and Fourier transform infrared spectroscopy (FT-IR) proved that the sensitivity of the C-O/C-O-O functional groups of the carbohydrates on the surface of the X-Com-ceramsite has a higher binding affinity toward MG as the initial concentration of MG changes.

Equilibrium Studies for Dye Adsorption onto Red Clay

In this study, it was aimed to remove malachite green, a cationic dye, from aqueous solutions by the adsorption method under various experimental conditions by using red clay. Red clay was used because it is abundant in nature and easily accessible in our region. In addition, it has been preferred as an adsorbent because it is used economically without any pre-treatment. The effects of initial malachite green concentration, temperature, adsorbent amount, and contact time on the adsorption process were evaluated. To examine the percent dye removal effect of the initial malachite green concentration, five different amounts of 25-150 ppm were examined. In order to examine the effect of the amount of red clay on the percentage of dye removal, five different amounts, in the range of 0.5-2 grams, were examined. In order to find the optimum time for the adsorption process, studies were carried out at four different values, 30-120 minutes. In the adsorption process of red clay and malachite green, experiments were carried out at three different degrees as 298, 313 and 333 K. After reaching equilibrium in the adsorption process, the data obtained were analyzed and studies were carried out by applying them to isotherm models. The results obtained from the adsorption process were compared with Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. It has been determined that the experimental studies are more compatible with the Dubinin-Radushkevich model. According to the results, it is incompatible with the Langmuir model. Accordingly, it can be said that the adsorption takes place in a multilayer and heterogeneous form.

Synthesis of Iron-containing Nanoparticles from Iron-Steel Industrial Waste for Adsorption of Malachite Green

For the synthesis of iron-containing nanoparticles (FeNPs), the iron ions were recovered from iron-steel industrial waste by leaching method followed by the chemical precipitation of ferric hydroxide with NH3. The ferric hydroxide was reduced pyrometallurgical to iron-containing nanoparticles by the reducing agent of CO generated from charcoal. FeNPs were characterized by XRD and SEM analysis. XRD results showed that FeNPs had predominantly face-centered cubic Fe3O4 structure, besides, the peaks of Fe2O3 and Fe0 structures were also observed. The particle size of FeNPs was calculated as 57.75 nm using Williamson–Hall equation. According to SEM images, FeNPs had homogeneous and spherical-like structures; also, the structures partially decomposed and the particle size increased due to the agglomeration of the particles after adsorption. FeNPs were used as an adsorbent for the removal of Malachite Green (MG). The experimental design and the optimization of experimental conditions were investigated by using response surface methodology (RSM) according to central composite design (CCD). The optimum experimental conditions were determined as 180 min contact time, 75 °C temperature, and 300 mg/L initial MG concentration. The agreement between the adsorbed MG concentrations at the equilibrium (qe) calculated from the model (148.43 mg/g) and determined experimentally (146.63 mg/g) under the optimum conditions showed that the selected model was suitable for MG adsorption by FeNPs. Langmuir isotherm model had higher R2 and lower ARE values than Freundlich isotherm model, showing that the equilibrium data of MG adsorption with FeNPs was the best agreement to Langmuir isotherm model with the maximum monolayer coverage capacity of 175.44 mg dye/g FeNPs. The thermodynamic studies suggested that the adsorption process was endothermic, spontaneous at the optimum conditions, and the positive ΔS value indicated the increased disorder at the solid-solution interface during the adsorption.

Adsorption of malachite green by calcined kaolin as adsorbent: optimization, thermodynamic and kinetics studies

The calcined kaolin was used as adsorbent, and the adsorption effect on malachite green (MG) was studied by changing the oscillation time, pH value, calcined kaolin dosage and temperature, respectively. The results show that calcined kaolin has good adsorption effect on MG. Under the conditions of oscillation time of 180 min, calcined kaolin dosage of 16 g/L, initial MG concentration of 100 mg/L and neutral pH, the MG adsorption rate could reach 98.9%. The adsorption equilibrium data of MG on calcined kaolin conformed to Langmuir and Freundlich isotherms. According to the results of adsorption thermodynamics, MG adsorption on calcined kaolin is endothermic and a spontaneous process. MG adsorption on calcined kaolin could be described by quasi-first-order better.

Efficient photocatalytic degradation of methyl orange and malachite green by Ag3PO4 decorated BiOBr nanoflower under visible light: Performance evaluation, mechanism insights and toxicology of the by-products

The development of an efficient and robust photocatalyst is of great importance for the effective treatment of toxic pollutants. In this study, novel Ag 3 PO 4 microspheres were decorated on the nanorod embedded flower-like BiOBr designed for the effective photodegradation of methyl orange (MO) and malachite green (MG) dyes. The synthesized particle was characterized to understand the structural and morphological features using HR-TEM, XRD, SEM, PL, ESR, FT-IR, XPS, EIS and N 2 adsorption and desorption. The degradation rate constants for MG (0.0132 min −1 ) were 3.47 and 3.14 times greater than BiOBr and Ag 3 PO 4 . Similarly, the rate constants for MO degradation (0.0151 min −1 ) are 3.87 and 3.97 times greater than BiOBr and Ag 3 PO 4 . The effect of initial MG and MO dye concentration, reaction pH, nanocomposite (NC) concentration was investigated. The NC exhibited excellent visible light photodegradation of 99.8% for MO and 93.4% for MG dyes at 180 min and 200 min respectively. A S-scheme heterojunction were proposed as the possible mechanism for the photodegradation of the dyes. The prepared photocatalyst exhibits excellent structural stability and reusability. The toxicity of the intermediates were predicted by the ecotoxicity analysis using ECOSAR software where the end products were less toxic than parent MG and MO. The degradation pathway were elucidated to predict the possible intermediates and to confirm the complete mineralization of the compound using GC-MS analysis. The proposed study can be implemented for practical application for the degradation of organic pollutants present in the water bodies. • Ag 3 PO 4 microspheres were decorated on the flower-like BiOBr. • BiOBr/30%Ag 3 PO 4 exhibited superior photodegradation of MO and MG dyes. • BiOBr/Ag 3 PO 4 shown excellent stability and recyclable properties. • Heterojunction of semiconductor accelerated separation of photoelectron-hole pairs.