Adsorption of malachite green from aqueous solution onto carbon prepared from Arundo donax root

Linear and nonlinear regression modelling of industrial dye adsorption using nanocellulose@chitosan nanocomposite beads

Nanocellulose@chitosan (nc@ch) composite beads were prepared via coagulation technique for the elimination of malachite green dye from aqueous solution. As malachite green dye is highly used in textile industries for dyeing purpose which after usage shows fatal effects to the ecosystems and human beings also. In this study the formulated nanocellulose@chitosan composite beads were characterized by Particle size analysis (PSA), Field emission scanning electron microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis were done to evaluate nanoparticles size distribution, morphological behaviour, functional group entities and degree of crystallinity of prepared beads. The nanocomposite beads adsorption performance was investigated for malachite green (MG) dye and BET analysis were also recorded to know about porous behaviour of the nanocomposite beads. Maximum removal of malachite green (MG) dye was found to be 72.0 mg/g for 100 ppm initial dye concentration. For accurate observations linear and non-linear modelling was done to know about the best-fitted adsorption model during the removal mechanism of dye molecules, on evaluating it has been observed that Langmuir isotherm and Freundlich isotherm show best-fitted observation in the case of linear and non-linear isotherm respectively (R2 = 0.96 & R2 = 0.957). In the case of kinetic linear models, the data was well fitted with pseudo-second-order showing chemosorption mechanism (R2 = 0.999), and in the case of non-linear kinetic model pseudo first order showed good fit showing physisorption mechanism during adsorption (R2 = 0.999). The thermodynamic study showed positive values for ΔH° and ΔS° throughout the adsorption process respectively, implying an endothermic behaviour. In view of cost effectiveness, desorption or regeneration study was done and it was showed that after the 5th cycle, the removal tendency had decreased from 48 to 38 % for 20-100 ppm dye solution accordingly. Thus, nanocomposite beads prepared by the coagulation method seem to be a suitable candidate for dye removal from synthetic wastewater and may have potential to be used in small scale textile industries for real wastewater treatment.

Kinetic and adsorption isotherm studies of Malachite Green dye onto surfactant-tailored alginate hydrogel beads: An influence of surfactant hydrophobicity

This study details the synthesis and characterization of surfactant-modified sodium alginate hydrogel beads crosslinked with Ba2+ ions through ionotropic gelation. Cationic surfactants such as, dodecyltrimethylammonium bromide (DTAB), didodecyldimethylammonium bromide (DDAB), and butanediyl-α,ω-bis-(dimethyldodecylammonium bromide) (GEM), were employed in the modification process. The surfactant-modified ALG-DTAB, ALG-DDAB, and ALG-GEM beads were investigated for the removal of cationic dye Malachite Green (MG) to elucidate the impact of hydrophobicity of amphiphiles on the adsorption process. The characterizations were carried out using Rheometry, Field Emission Scanning Electron Microscopy (FESEM), Infrared Spectroscopy (IR), and Energy Dispersive X-ray Spectroscopy (EDX). Under optimized conditions, ALG-GEM and ALG-DDAB demonstrated highest maximum adsorption capacity (Qmax > 700 mgg-1). The adsorption data fitted well to pseudo-second order kinetic and Langmuir adsorption models, suggesting the involvement of chemisorption phenomena with notable contributions from pore diffusion. The effects of pH, initial dye concentration, adsorbent dose, temperature, and competing ions on the removal of MG were investigated. Interestingly, ALG-GEM beads exhibited an increase in adsorption capacity with rising pH and a subsequent decrease with increasing temperature, showcasing optimal adsorption at pH 7.0 and 25 °C. The study proposes that ALG beads modified with cationic surfactants with higher hydrophobicity could offer a promising avenue in wastewater treatment processes.

A new and highly efficient CuMOF-based nanoenzyme and its application to the aptamer SERS/FL/RRS/Abs quadruple-mode analysis of ultratrace malachite green

Malachite green (MG) is highly toxic, persistent, and carcinogenic, and its widespread use is a danger to the ecosystem and a threat to public health and food safety, making it necessary to develop new sensitive multimode molecular spectroscopy methods. In this work, a new copper-based nanomaterial (CuNM) was prepared by a high-temperature roasting using a copper metal-organic framework (CuMOF) as precursor. The as-prepared CuNM was characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy, transmission electron microscopy (TEM), and BET surface area analysis. CuNM was found to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to produce the oxidation product TMBOX; however, subsequently, the MG aptamer (Apt) could be adsorbed on the CuNM surface by intermolecular interaction, which would inhibit the catalytic performance. After the addition of MG to be tested, the CuNM previously adsorbed by the Apt was transformed into its free state, thus restoring its catalytic activity. This new nanocatalytic indicator reaction could be monitored by surface-enhanced Raman scattering (SERS)/resonance Rayleigh scattering (RRS)/fluorescence (FL)/absorption (Abs) quadruple-mode methods. The SERS determination range was 0.004-0.4 nmol L-1 MG, with a limit of detection of 0.0032 nM. In this way, a rapid, stable, and sensitive method for the determination of MG residues in the environment was established.

Fabrication of calix[4]arene/polyurethane for the adsorptive removal of cationic dye from aqueous solutions

Calix[4]arene/polyurethane (C4PU) has been synthesized and characterized as an alternative adsorbent for the adsorption of methylene blue (MB) and malachite green (MG) dyes from the aqueous solution. C4PU was synthesized by reacting p-tert-butyl calix[4]arene with hexamethylene diisocyanate (HMDI) as the cross-linking agent. Different polymer ratios were synthesized, and C4PU-4 shows better adsorption than other ratios. The polymer was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) analysis, and point of zero charges (pHPZC). The isotherms and kinetics of the adsorption of MB and MG were studied under a range of experimental conditions, including pH, adsorbent dosage, initial dye concentration, and contact time. The adsorption was determined by the adsorption percentage of MB and MG dyes from the solution. The Langmuir isotherm model best describes the adsorption process for both dyes, and it follows a pseudo-second-order kinetic model, with the maximum adsorption capacity (qmax) of MB and MG, respectively, was found to be 1.991 mg·g-1 and 2.240 mg·g-1.

Versatile flexible SERS substrate for in situ detection of contaminants in water and fruits based on Ag NPs decorated wrinkled PDMS film

Flexible surface-enhanced Raman spectroscopy (SERS) substrate has attracted great attention due to its convenient sampling and on-site monitoring capability. However, it is still challenging to fabricate a versatile flexible SERS substrate, which can be used for in situ detection of analytes either in water or on irregular solid surfaces. Here, we report a flexible and transparent SERS substrate based on a wrinkled polydimethylsiloxane (PDMS) film obtained by transferring corrugated structures on the aluminium/polystyrene bilayer film, onto which silver nanoparticles (Ag NPs) are deposited by thermal evaporation. The as-fabricated SERS substrate exhibits a high enhancement factor (∼1.19×10⁵), good signal uniformity (RSD of 6.27%), and excellent batch-to-batch reproducibility (RSD of 7.3%) for rhodamine 6 G. In addition, the Ag NPs@W-PDMS film can maintain high detection sensitivity even after mechanical deformations of bending or torsion for 100 cycles. More importantly, being flexible, transparent, and light, the Ag NPs@W-PDMS film can both float on the water surface and conformally contact with the curved surface for in situ detection. The malachite green in aqueous environment and on apple peel can be easily detected down to 10^-6 M with a portable Raman spectrometer. Therefore, it is expected that such a versatile flexible SERS substrate has great potential in on-site, in situ contaminant monitoring for realistic applications.

Amazon raw clay as a precursor of a clay-based adsorbent: experimental study and DFT analysis for the adsorption of Basic Yellow 2 dye

A clay-based adsorbent (CBA) was purified from a sustainable precursor (raw clay, RC), which was obtained from the Amazon region in Brazil. The CBA was characterized using X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Brunauer-Emmet-Teller surface area (S_BET, RC = 23.386 m².g^-1, CBA = 33.020 m².g^-1), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), thermogravimetric analysis (TGA), cation exchange capacity (CEC, CBA = 44.75 cmol/kg), and point of zero charge analyses (pH_PZC, CBA = 2.20). Subsequently, CBA was used to adsorb basic yellow 2 (BY2) dye from aqueous solutions. A CBA dosage (1 g/L), initial concentration of dye (C₀ = 15 mg/L), and pH (5.6) were ideal conditions for the BY2 dye removal of ~ 98%. The BY2 kinetics was better represented by the pseudo-first-order (PFO) model while the BY2 equilibrium was well represented by the Sips model, with a maximum adsorption capacity of q_ms = 18.04 mg/g at 28 °C. The negative values of ΔG° and ΔH° showed that the studied process is spontaneous and exothermic, while the values of isosteric heat (∆H_st, -16 to -20 kJ/mol) suggest a predominance of physical interactions. The molecular chemical reactivity of BY2 was investigated using quantum chemical descriptors calculated based on Density Functional Theory (DFT) optimization of the dye molecule, and the results revealed a large energy gap value (4.3900 eV) and considerable chemical hardness (η = 2.1950 eV). Therefore, the correlation between DFT and experimental results consistently sustains that BY2 dye tends to be adsorbed on the CBA surface by electrostatic interactions, thus, this is the possible adsorption mechanism of this process.

Biosorption of Triphenyl Methane Dyes (Malachite Green and Crystal Violet) from Aqueous Media by Alfa (Stipa tenacissima L.) Leaf Powder

This study includes the characterization and exploitation of an abundant agricultural waste in Algeria, Alfa (Stipa tenacissima L.) leaf powder (ALP) as a biosorbent for the removal of hazardous triphenylmethane dyes, malachite green (basic green 4) and crystal violet (basic violet 3), from aqueous media under various operating conditions in batch mode. The effect of experimental parameters such as initial dye concentration (10-40 mg/L), contact time (0-300 min), biosorbent dose (2.5-5.5 g/L), initial pH (2-8), temperature (298-328 K), and ionic strength on dye sorption was investigated. The results of both dyes show that the increase in initial concentration, contact time, temperature, and initial pH of solution leads to an increase in biosorbed quantity, unlike the effect of ionic strength. The biosorption kinetics for triphenylmethane dyes on ALP was analyzed by pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models proposed by the Weber-Morris equation. Equilibrium sorption data were analyzed by six isotherms, namely the Langmuir, Freundlich, Harkins-Jura, Flory-Huggins, Elovich, and Kiselev isotherms. The thermodynamic parameters were evaluated for both dyes. The thermodynamic results suggest that both dyes' biosorption is a typical physical process, spontaneous and endothermic in nature.

Olive oil-based quercetin nanoemulsion (QuNE)'s interactions with human serum proteins (HSA and HTF) and its anticancer activity

The current study produced Quercetin nanoemulsions (QuNEs) for the purpose of improving Quercetin solubility in an aqueous polar condition and to analyze QuNE-protein formation (QuNE-human serum albumin (HSA) and QuNE-holo-transferrin (HTF)).QuNE was produced by utilizing an ultrasound-based emulsification method and was characterized by DLS, TEM, and SEM. Its interaction with HSA and HTF proteins was studied by analyzing the results of FRET and RLS spectroscopy, Stern-Volmer plotting, the Van't Hoff equation, CD spectroscopy, and molecular docking methods. Finally, QuNE's cytotoxic impact, cell death type induction, and antioxidant properties were evaluated by applying an MTT assay on a human hepatocyte cancer cell (HepG2), measuring Cas-3 gene expression, and conducting a DPPH antioxidant test, respectively. Compared to the non-entrapped Quercetin, Quercetin-entrapped nano-emulsions formed stable complexes with HSA and HTF by improving hydrophilic-hydrophobic interactions. The binding constant (BC), ΔH⁰, and ΔS⁰ indices for both the QuNE-HSA and QuNE-HTF complexes were measured at (4.92 × 105 and 11.99 × 104 M^-1), (170.96 and -131.19 KJ.mol^-1), and (-464.86 and 342.83J.mol^-1K^-1), respectively.QuNE lowered the HepG2 viability by up-regulating Cas-3 gene expression and thus inducing apoptosis. Moreover, a notable antioxidant impact on the QuNE was detected. Due to its ability in delivering Quercetin to HSA and HTF proteins and stabilizing their protein complexes, QuNE can be used as a suitable primary transporting agent whose formation of stable bio-accessible QuNE-HSA and -HTF protein complexes creates a safe and natural secondary delivery system, which has potential to be used as an efficient anticancer compound.Communicated by Ramaswamy H. Sarma.

Reduced Graphene Oxide-Zinc Sulfide Nanocomposite Decorated with Silver Nanoparticles for Wastewater Treatment by Adsorption, Photocatalysis and Antimicrobial Action

Reduced graphene oxide nanosheets decorated with ZnS and ZnS-Ag nanoparticles are successfully prepared via a facile one-step chemical approach consisting of reducing the metal precursors on a rGO surface. Prepared rGO-ZnS nanocomposite is employed as an adsorbent material against two model dyes: malachite green (MG) and ethyl violet (EV). The adsorptive behavior of the nanocomposite was tuned by monitoring some parameters, such as the time of contact between the dye and the adsorbent, and the adsorbent dose. Experimental data were also simulated with kinetic models to evaluate the adsorption behavior, and the results confirmed that the adsorption of both dyes followed a pseudo 2nd order kinetic mode. Moreover, the adsorbent was also regenerated in a suitable media for both dyes (HCl for MG and ethanol for EV), without any significant loss in removal efficiency. Ag doped rGO-ZnS nanocomposite was also utilized as a photocatalyst for the degradation of the selected organic contaminant, resorcinol. The complete degradation of the phenolic compound was achieved after 60 min with 200 mg of rGO-ZnS-Ag nanocomposite under natural sunlight irradiation. The photocatalytic activity was studied considering some parameters, such as the initial phenol concentration, the photocatalyst loading, and the pH of the solution. The degradation kinetics of resorcinol was carefully studied and found to follow a linear Langmuir-Hinshelwood model. An additional advantage of rGO-ZnS and rGO-ZnS-Ag nanocomposites was antibacterial activity against Gram-negative bacterium, E. coli, and the results confirmed the significant performance of the nanocomposites in destroying harmful pathogens.

Removal of Malachite Green Dye from Aqueous Solution by Catalytic Wet Oxidation Technique Using Ni/Kaolin as Catalyst

In this study, natural Algerian kaolin was used as a support and impregnated with nickel at different loading amounts (2 wt.%, 5 wt.%, and 7 wt.%) in order to prepare a supported catalyst. The wet impregnation technique was used in this preparation; nickel oxide (NiO) was the active phase precursor of the catalyst, and the catalysts were designated as follows: 2%, 5%, and 7% Ni/kaolin. These catalysts were put to the test in catalytic wet peroxide oxidation (CWPO) for degrading the organic contaminant malachite green dye (MG). Analytical techniques such as FTIR spectroscopy, X-ray diffraction, BET, and X-fluorescence were used to examine the structure, morphology, and chemical composition of the support and the produced catalysts. Several parameters, including temperature, catalytic dose, metal loading, hydrogen peroxide volume, and kinetic model were systematically investigated. The combination of improved parameters resulted in a significant increase in the catalytic activity, achieving a high removal rate of MG dye of 98.87%.

Characterization and adsorption of malachite green dye from aqueous solution onto Salix alba L. (Willow tree) leaves powder and its respective biochar

In the present study, the use of low-cost, highly efficient, eco-friendly, and abundantly available (in Kashmir region, J&K India) willow leaves from which adsorbents like willow leaves powder (WLP) and willow leaves biochar (WLB) were prepared, have been found to be efficient for malachite green (MG) dye removal and can be used as an alternative to the current expensive methods of removing the same dye from an aqueous solution. The techniques like Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and carbon, hydrogen, nitrogen, sulphur (CHNS) analyser were used to characterize the samples without any chemical treatment. SEM of the adsorbents shows the presence of different sized pores, cracks, and crevices. FTIR and CHNS show functional groups and elemental concentration, respectively. The effects of various experimental parameters such as contact time, adsorbent dosage, initial dye concentration, salt treatment, and pH were investigated and optimal experimental conditions were obtained. It has been found that Langmuir, Freundlich, and Temkin isotherms were useful for describing the equilibrium of adsorption system. The equilibrium adsorption data in this research work was found to follow both Langmuir and Freundlich isotherm models and maximum monolayer capacity of WLP and WLB were found to be 10.014 and 21.244 mg/g, respectively. The experimental data for both WLP and WLB followed pseudo-second-order kinetic model with R²= 0.999. Intraparticle diffusion model reveals that more than one mechanism influenced the adsorption process. Thermodynamic study concluded that the adsorption is spontaneous for both adsorbents but exothermic for WLP and is endothermic in nature for WLB. Present exploration and comparison with other reported adsorbents concluded that, WLP and WLB may be useful as low-cost attractive option for the removal of MG dye from aqueous solution and therefore, also from wastewater containing MG dye.

Integrated experimental and theoretical insights for Malachite Green Dye adsorption from wastewater using low cost adsorbent

Water pollution is one of the problems that threaten humanity, and to confront it with only experimental procedures is not enough. It is necessary to integrate both practical methods and theoretical calculations to achieve decontamination with the most accurate interpretation. Hence, discussing the experimental mechanism study of Malachite Green (MG) dye adsorption with the help of the application of density functional theory (DFT) calculations is the main goal of this article. The experimental results affirmed that the preparation of γ-Al₂O₃ by precipitation method using (NH₄)₂CO₃ improved the porosity, the surface capability, and the adsorbent capacities (q_max = 210 mg/g) at optimum condition compared with the previous studies. Kinetic and equilibrium studies showed that the adsorption follows the pseudo-second-order model and Freundlich isotherm model, respectively. Also, the calculated and observed thermodynamic parameters exerted positive values of ΔH° and ΔS°, which translates into an endothermic process with increasing disorder of the system. Theoretical calculations at DFT- B3LYP/6-31G (d,P) level of theory were calculated to show the selectivity of using the cationic form of MG in the experimental measurements to find the interaction mechanism. The electronic structure and intramolecular charge transfer of MG, its cationic form and the complex of MG-Al were investigated theoretically at the B3LYP/6-31 G (d,p) level of theory. The equilibrium geometries of MG, its cationic form and the complex of MG-Al were determined, and it was found that these geometries are non-planar. The E_HOMO and E_LUMO energies can be used to calculate the global properties; chemical hardness (η), softness (S) and electronegativity (χ). The calculated non-linear optical parameters (NLO) of the studied compounds, the electronic dipole moment (μ), first-order hyperpolarizability (β), the hyper-Rayleigh scattering (β_HRS) and the depolarization ratio (DR), showed promising optical properties. Finally, the computational and the experimental results indicated that the adsorption efficiency of MG from wastewater was directly associated with the dye electrophilicity power.

Facile and scalable preparation of ZIF-67 decorated cotton fibers as recoverable and efficient adsorbents for removal of malachite green

Recently, metal–organic frameworks (MOFs) have received considerable attention as highly efficient adsorbents for dye wastewater remediation. However, the immobilization of MOFs on the substrate surfaces to fabricate easy recyclable adsorbents via a facile route is still a challenge. In this work, ZIF-67/cotton fibers as adsorbents for dye removal were prepared in a large-scale using a simple coordination replication method. The successful fabrication of the ZIF-67/cotton fibers was confirmed by FTIR, XRD, XPS, SEM and BET analysis, respectively. As expected, the as-prepared ZIF-67/cotton fibers exhibited high adsorption capacity of 3787 mg/g towards malachite green (MG). Meanwhile, the adsorption kinetics and isotherm obeyed the pseudo-second-order kinetics and Langmuir model, respectively. Moreover, its removal efficiency towards MG was not significantly influenced by the pH and ionic strength of aqueous solution. Most importantly, the ZIF-67/cotton fibers can remove MG from synthetic effluents, and it can be easily regenerated without filtration or centrifugation processes, with the regeneration efficiency remaining over 90% even after 10 cycles. Additionally, the ZIF-67/cotton fibers presented excellent antimicrobial performance against E. coli and S. aureus. Hence, the distinctive features of the as-prepared ZIF-67/cotton fibers make it promisingly applicable for the colored wastewater treatment.

Utilization of a Novel Low-Cost Gibto (Lupinus Albus) Seed Peel Waste for the Removal of Malachite Green Dye: Equilibrium, Kinetic, and Thermodynamic Studies

The aim of this study was to investigate the adsorption characteristics of malachite green (MG) dye onto the raw (RLAPW) and activated (ALAPW) surface of Lupinus albus seed peel waste prepared via physicochemical activation under alkaline condition as a dye adsorbent. Proximate analysis, surface area (Sears’ method), point of zero charge (pHzpc), and FTIR analysis were used to characterize the adsorbents. The effects of operational parameters such as pH (4) for ALAPW and pH (6) for RLAPW, adsorbent dose (0.2 g), initial dye concentration (30 mg/L), contact time (60 min), and temperature (298 K) were optimized. The experimental data well fitted with the Freundlich adsorption isotherm with the adsorption capacity of 7.3 mg/g for activated Lupinus albus seed peel waste (ALAPW) and Sips isotherm for raw Lupinus albus seed peel waste (RLAPW) with the adsorption capacity of 6.6 mg/g. The kinetics data well fitted to pseudo-second-order kinetic model for both adsorbents. Thermodynamic study revealed that the bioadsorption process using bioadsorbents was spontaneous and exothermic in nature. Desorption experiment was conducted and showed desorption efficiency at an acidic pH of 2. The results showed that the prepared adsorbents exhibited good adsorption capacity and can be used as an alternative adsorbent for the adsorptive removal of malachite green dyes.

Production of activated carbon from Elaeagnus angustifolia seeds using H3PO4 activator and methylene blue and malachite green adsorption

In this study, activated carbon was obtained from Elaeagnus angustifolia seeds and its usability in the adsorption of methylene blue (MB) and malachite green (MG) from aqueous solution was investigated. Activated carbon was synthesized by chemical activation method using H₃PO₄ as an activator. In the synthesis of the activated carbon, the effects of various parameters such as the rate of impregnation, duration of activation, temperature of activation and duration of activation were investigated. The characterization of the synthesized activated carbons was carried out by FTIR, SEM and BET analyses and the surface area of the produced activated carbon was determined to be 1,194 m² g^-1. The effects of solution initial pH, solution initial concentration and amount of activated carbon on MB and MG adsorption were investigated. The adsorption capacity was found to be higher when the pH of the solution was 8 for MB and 4 for MG. The adsorption kinetics of MB and MG were found to fit the Elovich kinetic model and pseudo-first-order kinetic model, respectively. Adsorption equilibrium data were found to be compatible with Langmuir isotherm for both dyes. According to the Langmuir isotherm, q_max adsorption capacity was found to be 72 mg/g and 115 mg/g for MB and MG, respectively. Novelty Activated carbon was obtained from Elaeagnus angustifolia seeds and its usability in the adsorption of methylene blue (MB) and malachite green (MG) from aqueous solution was investigated. A high surface area activated carbon was synthesized. The surface area of the produced activated carbon was determined to be 1,194 m² g^-1. According to the Langmuir isotherm, q_max adsorption capacity was found to be 72 mg/g and 115 mg/g for MB and MG, respectively. It has been determined that the adsorption capacity of synthesized activated carbon is high.

Bioprocessing strategies for cost-effective simultaneous removal of chromium and malachite green by marine alga Enteromorpha intestinalis

A large number of industries use heavy metal cations to fix dyes in fabrication processes. Malachite green (MG) is used in many factories and in aquaculture production to treat parasites, and it has genotoxic and carcinogenic effects. Chromium is used to fix the dyes and it is a global toxic heavy metal. Face centered central composite design (FCCCD) has been used to determine the most significant factors for enhanced simultaneous removal of MG and chromium ions from aqueous solutions using marine green alga Enteromorpha intestinalis biomass collected from Jeddah beach. The dry biomass of E. intestinalis samples were also examined using SEM and FTIR before and after MG and chromium biosoptions. The predicted results indicated that 4.3 g/L E. intestinalis biomass was simultaneously removed 99.63% of MG and 93.38% of chromium from aqueous solution using a MG concentration of 7.97 mg/L, the chromium concentration of 192.45 mg/L, pH 9.92, the contact time was 38.5 min with an agitation of 200 rpm. FTIR and SEM proved the change in characteristics of algal biomass after treatments. The dry biomass of E. intestinalis has the capacity to remove MG and chromium from aquatic effluents in a feasible and efficient manner.

Microbial degradation, spectral analysis and toxicological assessment of malachite green by Streptomyces chrestomyceticus S20

Malachite green (MG), a triphenylmethane dye is extensively used for coloring silk, aquaculture and textile industries, it has also has been reported toxic to life forms. This study aimed to investigate the biodegradation potential of MG by actinobacteria. The potent actinobacterial strain S20 used in this study was isolated from forest soil (Sabarimala, Kerala, India) and identified as Streptomyces chrestomyceticus based on phenotype and molecular features. Strain S20 degraded MG up to 59.65 ± 0.68% was studied in MSM medium and MG (300 mg l^-1) and degradation was increased (90-99%) by additions of 1% glucose and yeast extract into the medium at pH 7. The treated metabolites from MG by S20 characterized by FT-IR and GC-MS. The results showed MG has been degraded into nontoxic compounds evaluated by (1) phytotoxic assay on Vigna radiata, (2) microbial toxicity on Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus, Streptococcus sp. and Escherichia coli, (3) cytotoxicity assay in a human cell line (MCF 7). The toxicity studies demonstrated that the byproducts from MG degradation by S. chrestomyceticus S20 were no toxic to plants and microbes and less toxic to human cells as compared to the parent MG. Perhaps this is the first work reported on biodegradation of MG by S. chrestomyceticus which could be a potential candidate for the removal of MG from various environments.

A Novel Nanocomposite of Activated Serpentine Mineral Decorated with Magnetic Nanoparticles for Rapid and Effective Adsorption of Hazardous Cationic Dyes: Kinetics and Equilibrium Studies

A widely distributed mineral, serpentine, obtained from Wadi Ghadir (Eastern Desert in Egypt) was studied as a potential naturally and abundantly available source for the synthesis of an efficient adsorbent for aquatic remediation applications. A novel nanocomposite was synthesized after the exfoliation of the layered structure of serpentine by hydrogen peroxide treatment (serpentine (SP)), followed by decoration with magnetic Fe3O4 nanoparticles (MNP). The goal behind the utilization of the latter phase was to increase the environmental remediation capability and to incorporate magnetic properties at the final adsorbent, toward a better separation after the use. The fabricated composite (MNP/SP) was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The composite's potential adsorption application toward the removal of two cationic dyes, methylene blue (MB) and malachite green (MG), was investigated. The observed adsorption kinetics was fast, and the highest uptake was observed at pH = 8, with the capacities to reach 162 and 176 mg g-1 for MB and MG, respectively, values significantly higher than various other materials tested against these two cationic dyes. Compared to hydrogen peroxide-treated serpentine, the removal efficiency of the composite was higher by 157 and 127% for MB and MG, respectively. The MB and MG were adsorbed because of the favorable electrostatic interactions between MNP/SP active sites and the cationic dyes. The close value capacities suggest that the difference in chemistry of the two dyes does not affect the interactions, with the later occurring via the dyes' amine functionalities. With increasing ionic strength, the adsorption of the studied basic dyes was slightly decreased, suggesting only partial antagonistic ion effect. The sorbent can be easily regenerated and reused without significant deterioration of its adsorption efficiency, which makes MNP/SP a promising adsorbent for the removal of hazardous pollutants from aquatic environments.

Equilibrium, Kinetics, and Thermodynamic Studies of Malachite Green Adsorption onto Fig (Ficus cartia) Leaves

The release of dyes from dying industries such as leather, paper, and textiles is an important cause of environmental pollution. In the present study, the batch adsorption measurements were carried out using stimulated aqueous solutions and the effect of operating variables such as initial malachite green concentration, amount of adsorbent, solution pH, contact time, and solution temperature, were investigated. The experimental result showed that the percentage removal decreased with an increase in initial dye concentration but increased as pH of the solution, contact time, and adsorbent dose increased. The equilibrium data were analyzed using Langmuir adsorption isotherm, Freundlich adsorption isotherm, and Tempkin isotherm models, and it was observed that the Langmuir adsorption isotherm better described the adsorption process. The monolayer adsorption capacity of activated carbon prepared from fig leaves for malachite green adsorption was found to be 51.79 mg/g at 298 K. Furthermore, the adsorption kinetics of the dye was investigated, and the rate of adsorption was found to follow the pseudo-first-order kinetic model with intraparticle diffusion as one of the rate-determining steps. The negative value of ΔG ⁰ and the positive values of ΔH ⁰ indicate the spontaneous and endothermic nature of the adsorption process, respectively. The experimental result obtained in the present study and comparison with other reported adsorbents indicate that activated carbon prepared from fig leaves could be used as a low-cost alternative adsorbent for the removal of malachite green from aqueous solution.

Experimental investigation of activated carbon prepared from apricot stones material (ASM) adsorbent for removal of malachite green (MG) from aqueous solution

The adsorption of malachite green onto activated carbon prepared from apricot stones material has been investigated at batch conditions. The effects of contact time (0–60 min), initial pH (3–11), agitation speed (100–700 r/min), temperature (298–343 K), adsorbent dose (1–10 g/L), and malachite green concentration (4.45–17.6 mg/L) on the malachite green adsorption by apricot stones material have been studied. Malachite green removal increases over the contact time until equilibrium. The batch adsorption experiments were carried out to optimize the physical parameters on the malachite green removal efficiency. It has been found that 23.80 mg/g at 25°C and 88.05 mg/g at 70°C were removed. The kinetic parameters, rate constants and equilibrium adsorption capacities, were calculated and discussed for each kinetic model. The adsorption of malachite green onto apricot stones material is well described by the pseudo second-order equation. The experimental isotherm data were analyzed by different models; the adsorption follows the Langmuir model, providing a better fit of the equilibrium data. The thermodynamics parameters such as the negative free energy Δ G° (−0.191 to −4.447 kJ/mol) and positive enthalpy Δ H° (50.86 kJ/mol) indicated the spontaneous and endothermic nature of the malachite green adsorption with a chemisorption process.

A novel hierarchical stiff carbon foam with graphene-like nanosheet surface as the desired adsorbent for malachite green removal from wastewater

A novel hierarchical stiff carbon foam (HSCF) was successfully prepared via a carbothermal reduction between the carbon foam with two-level pore structure and the Al₂O₃ from aluminum sulfate, and used as a bulk adsorbent for removing malachite green (MG) dye. The structures of the HSCF were characterized using SEM, XRD, FTIR, BET, and XPS, and the effects of adsorption condition on the MG removal were studied through batch adsorption experiments. Results show that large-sized and complex-shaped HSCF can be easily fabricated with a high compression strength of 1.58 MPa at a low bulk density (0.10 g cm^-3). The HSCF possesses a fluffy graphene-like nanosheet surface with a mesoporous structure and meanwhile exhibits good hydrophilicity loaded with aluminum hydroxide. The experimental maximum adsorption capacity for MG reaches 425.2 mg g^-1 with a relatively high partition coefficient of 9.38 mg g^-1 μM^-1 at the optimal condition. The experimental data are in good agreement with Langmuir isotherm and pseudo-second-order kinetic model, and meanwhile, the adsorption of MG onto the HSCF is a spontaneous and endothermic process. Also, the HSCF still exhibits good adsorption ability and stability after seven regeneration cycles.

Application of immobilized ZnO nanoparticles for the photocatalytic regeneration of ultrasound pretreated-granular activated carbon

In this study, the photocatalytic regeneration by ZnO was employed for the regeneration of the granular activated carbon (GAC) which was saturated with the reactive red 43. The ultrasound was applied as a pretreatment step due to the cleanup of the adsorbent surface and providing a higher surface area and adsorption capacity. According to the nitrogen gas adsorption-desorption results, the ultrasound pretreated-GAC had the highest surface area and the total pore volume. The SEM and XRD analyses confirmed the immobilization of ZnO nanoparticles on the GAC. Response surface methodology (RSM) was used to model and optimize the preparation of the granular activated carbon/ZnO nanocomposite. The sonication time, pH, GAC/ZnO ratio, and calcination temperature were used as four effective parameters on nanocomposite preparation. Optimum amounts of pH, GAC/ZnO ratio, calcination temperature, and sonication time were found to be equal to 4, 5, 300 °C, 210 min, respectively; in these conditions, 83.98% of the capacity of the exhausted granular activated carbon was regenerated. ANOVA results, high R², R²-adj values, and also normal and random distribution of residuals showed that application of RSM for the modeling and optimizing the preparation step of GAC/ZnO nanocomposite was successful.

Kinetics and thermodynamic studies for removal of methylene blue dye by biosynthesize copper oxide nanoparticles and its antibacterial activity

The present study deals with the green approach for the biosynthesis of copper oxide-Aloe vera (CuO-A) based nanoparticles using leaf extract of Aloe barbadensis miller. Synthesized nanoparticles were characterized through different techniques like TEM and FTIR. As the size decreases and surface area increases, these are prominently used as a very good adsorbent. The effects of different parameters like adsorbent dosage, pH, contact time, initial dye concentration and temperature are optimised to get the maximum removal of methylene blue dye from the solution. The maximum dye removal was found to be 98.89% with initial concentration of 100 mg/L at alkaline pH in 210 min., with shaking speed of 150 rpm. The Langmuir result reveals a better consistency than the Freundlich model with 95.5 mg/g. Lagergren's model was used to study the kinetics of the system. Mechanistic behaviour was study through intra-particle diffusion study and Boyd plot. Thermodynamic study showed spontaneous and endothermic nature of the adsorption. Furthermore, synthesized CuO-A nanoparticles showed good antibacterial activity against different strains of bacteria. The zone of inhibition was found to be 11 mm, 12 mm, 8 mm and 9 mm in Pseudomonas, Klebsiella, Staphylococcus and E.coli, respectively.

Resolution of mixed dyes by in situ near infrared (NIR) spectroelectrochemistry

NIR spectroelectrochemistry has scarcely been used for deconvolving aqueous mixtures due to the water restriction in this spectral range. However, this work offers an interesting approach for the study of mixtures of molecules with similar electrochemical and spectroscopic behaviour by overcoming the limitations of this hybrid technique. As a proof of concept, the resolution of mixtures of two dyes with similar chemical structures demonstrates the usefulness of NIR spectroelectrochemistry.

Adsorption of Malachite Green Dye from Liquid Phase Using Hydrophilic Thiourea-Modified Poly(acrylonitrile-co-acrylic acid): Kinetic and Isotherm Studies

Thiourea-modified poly(acrylonitrile-co-acrylic acid) (TU-poly(AN-co-AA)) adsorbent was a surface modification of poly(acrylonitrile-co-acrylic acid) synthesized by facile redox polymerization. Surface functionalization with thiourea was carried out to provide hydrophilicity on the surface of a polymeric adsorbent. Fourier transform infrared (FTIR) spectrometer, scanning electron microscope (SEM), and Zetasizer characterized the morphology and structures of TU-poly(AN-co-AA). Copolymerization of poly(acrylonitrile-co-acrylic acid) and its successful incorporation of the thioamide group was confirmed by the FTIR spectra. The SEM micrographs depicted uniform and porous surface morphologies of polymeric particles. The average diameter of modified and unmodified poly(acrylonitrile-co-acrylic acid) was 289 nm and 279 nm, respectively. Zeta potentials of TU-poly(AN-co-AA) revealed the negatively charged surface of the prepared polymer. Adsorption capacities of hydrophilic TU-poly(AN-co-AA) were investigated using malachite green (MG) as an adsorbate by varying experimental conditions (pH, initial concentration, and temperature). Results showed that the pseudo-second-order reaction model best described the adsorption process with chemisorption being the rate-limiting step. Furthermore, Elovich and intraparticle diffusions play a significant role in adsorption kinetics. The equilibrium isotherm has its fitness in the following order: Freundlich model > Temkin model > Langmuir model. Thermodynamic analysis indicates that the sorption process is spontaneous and exothermic in nature. The reusability results suggested potential applications of the TU-poly(AN-co-AA) polymer in adsorption and separation of cationic malachite green dye from wastewater.

Rhizofiltration system consists of chitosan and natural Arundo donax L. for removal of basic red dye

Arundo donax L. (A. donax) plant, which are naturally grown, is capable of removing heavy metals, toxins and dyes from the environment. In addition the cell structure A. donax enable the whole to make phytoremdation for the most of environmental pollutions. For that reasons, the A. donax cells were obtained and dispersed in polymer compost to form what is called bio-chemical/dye removing system. In details; Polymeric beads were fabricated from natural low cost materials of chitosan (Cs), A. donax (cells), gelatin (GP) and poly vinyl pyrrolidone (PVP) to be applied as a powerful sorbent for CI Basic Red 14 dye. The morphological structure of the fabricated beads was investigated by Scanning Electron Microscope (SEM) and the results revealed that most immobilized A. donax cells into beads and micro-clusters are formed inside the beads. The effect of experimental variables such as sorbent dose, initial dye concentration, pH, and contact time were investigated. Freundlich and Langmuir isotherm models were applied to describe sorbent-dye sorption system. Equilibrium isotherms of CI Basic Red 14 dye on the fabricated beads were obtained, where the first-order rate model is more appropriate.