Study of competitive adsorption of malachite green and sunset yellow dyes on cadmium hydroxide nanowires loaded on activated carbon

Synthesis & fabrication of O-linked polymeric hybrids for recovery of textile dyes: Closed loop economy

Dyes are an important resource employed for the production systems in textile, paper, paint and leather industry. An estimate of 200,000 tons of dyes are discharged as textile effluent each year worldwide. It becomes imperative to recover these dyes by treating the effluents using economically viable routes. The present research was undertaken with the objective to attain zero emission and zero waste through development of novel polymeric hybrids as adsorbents. For this purpose, metal moieties (Al3+, Si4+, Ti4+ and Zr4+) were hybridized with polyacrylic acid, and cellulose acetate for the uptake of selected dyes under optimized parameters. The structural elucidation of four synthesized hybrids (MP-Al, MP-Si, MP-Ti and MP-Zr) by FTIR, EDX and TGA confirmed O-linked grafting of metal moieties with polymers and thermally stable porous materials. SEM micrographic images displayed void spaces providing channels for effective adsorption. The batch experiments demonstrated removal of malachite green (77-96%) and congo red (70-82%) upon contact of initial 45 min on polymeric hybrids On the other hand, pristine polyacrylic acid and cellulose acetate showed remarkably low removal of dyes. The adsorption mechanism is proposed as physical in nature following type II isotherm. Further, Langmuir and Ho's pseudo second order fitness was evaluated. In order to determine the economic viability of the present research, the real textile dyes were recovered in three consecutive cycles of adsorption and chemical treatment of hybrids. The results propose a system with positive impact on economy by maximum utilization of hybrids as adsorbents and recovery of textile dyes for reuse in textile processing.

Magnetic Activated Carbon from ZnCl2 and FeCl3 Coactivation of Lotus Seedpod: One-Pot Preparation, Characterization, and Catalytic Activity towards Robust Degradation of Acid Orange 10

Lotus seedpods (LSPs) are an abundant and underutilized agricultural residue discarded from lotus seed production. In this study, ZnCl₂ and FeCl₃ coactivation of LSP for one-pot preparation of magnetic activated carbon (MAC) was explored for the first time. X-ray diffraction (XRD) results showed that Fe₃O₄, Fe⁰, and ZnO crystals were formed in the LSP-derived carbon matrix. Notably, transmission electron microscopy (TEM) images showed that the shapes of these components consisted of not only nanoparticles but also nanowires. Fe and Zn contents in MAC determined by atomic absorption spectroscopy (AAS) were 6.89 and 3.94 wt%, respectively. Moreover, S_BET and V_total of MAC prepared by coactivation with ZnCl₂ and FeCl₃ were 1080 m²/g and 0.51 cm³/g, which were much higher than those prepared by single activation with FeCl₃ (274 m²/g and 0.14 cm³/g) or ZnCl₂ (369 m²/g and 0.21 cm³/g). MAC was subsequently applied as an oxidation catalyst for Fenton-like degradation of acid orange 10 (AO10). As a result, 0.20 g/L MAC could partially remove AO10 (100 ppm) with an adsorption capacity of 78.4 mg/g at pH 3.0. When 350 ppm H₂O₂ was further added, AO10 was decolorized rapidly, nearly complete within 30 min, and 66% of the COD was removed in 120 min. The potent catalytic performance of MAC might come from the synergistic effect of Fe⁰ and Fe₃O₄ nanocrystals in the porous carbon support. MAC also demonstrated effective stability and reusability after five consecutive cycles, when total AO10 removal at 20 min of H₂O₂ addition slightly decreased from 93.9 ± 0.9% to 86.3 ± 0.8% and minimal iron leaching of 1.14 to 1.19 mg/L was detected. Interestingly, the MAC catalyst with a saturation magnetization of 3.6 emu/g was easily separated from the treated mixture for the next cycle. Overall, these findings demonstrate that magnetic activated carbon prepared from ZnCl₂ and FeCl₃ coactivation of lotus seedpod waste can be a low-cost catalyst for rapid degradation of acid orange 10.

Zinc Oxide Nanoparticles and Their Application in Adsorption of Toxic Dye from Aqueous Solution

Dye waste is one of the most serious types of pollution in natural water bodies, since its presence can be easily detected by the naked eye, and it is not easily biodegradable. In this study, zinc oxide nanoparticles (ZnO-NPs) were generated using a chemical reduction approach involving the zinc nitrate procedure. Fourier transform infrared (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), and UV-vis techniques were used to analyse the surface of ZnO-NPs. The results indicate the creation of ZnO-NPs with a surface area of 95.83 m2 g−1 and a pore volume of 0.058 cm3 g−1, as well as an average pore size of 1.22 nm. In addition, the ZnO-NPs were used as an adsorbent for the removal of Ismate violet 2R (IV2R) dye from aqueous solutions under various conditions (dye concentration, pH, contact time, temperature, and adsorbent dosage) using a batch adsorption technique. Furthermore, FTIR and SEM examinations performed before and after the adsorption process indicated that the surface functionalisation and shape of the ZnO-NP nanocomposites changed significantly. A batch adsorption analysis was used to examine the extent to which operating parameters, the equilibrium isotherm, adsorption kinetics, and thermodynamics affected the results. The results of the batch technique revealed that the best results were obtained in the treatment with 0.04 g of ZnO-NP nanoparticles at 30 °C and pH 2 with an initial dye concentration of 10 mg L−1, which removed 91.5% and 65.6% of dye from synthetic and textile industry effluents, respectively. Additionally, six adsorption isotherm models were investigated by mathematical modelling and were validated for the adsorption process, and error function equations were applied to the isotherm model results in order to find the best-fit isotherm model. Likewise, the pseudo-second-order kinetic model fit well. A thermodynamic study revealed that IV2R adsorption on ZnO-NPs is a spontaneous, endothermic, and feasible sorption process. Finally, the synthesised nanocomposites prove to be excellent candidates for IV2R removal from water and real wastewater systems.

Biochars and activated carbons as adsorbents of inorganic and organic compounds from multicomponent systems - A review

Biochars are obtained by biomass pyrolysis, whereas activated carbon is a biochar that has undergone chemical or physical activation. Owing to the large surface area and easy surface modification both solids are widely applied as adsorbents. They are low-costs materials, they could be regenerated and their disposal is not troublesome. Adsorption of heavy metals, dyes, pharmaceuticals on the surface of biochars and activated carbons, from simple systems of adsorbate containing only one compound, are described extensively in the literature. The present paper provides an overview of reports on adsorption of inorganic and organic compounds onto these two types of adsorbents from the mixed adsorbate systems. The described adsorbate systems have been divided into those consisting of: two or more inorganic ions, two or more organic compounds and both of them (inorganic and organic ones). The research of this type is carried out much less frequently due to the more complicated description of interactions in the mixed adsorbate systems.

Synthesis and characterization of solid-state Fe-exchanged nano-bentonite and evaluation of methyl orange adsorption

A new adsorbent was synthesized using ion-exchange between iron salts and bentonite modified with acetyl trimethylammonium bromide (CTAB) in the solid phase. Ion-exchange was performed in the solid state at a temperature of 100 °C for 2 min. Various analyses such as X-ray diffraction (XRD), scanning electron microscopy (SEM), porosity measurement (BET), infrared Fourier transform (FT-IR), transmission electron microscopy (TEM), X-ray energy diffraction (EDX), and thermal weighing (TGA) were used to characterize the synthesized nano-adsorbents. Under optimal conditions (pH = 7, time 60 min, concentration of dye solution 150 ppm, and amount of nano-adsorbent 0.75 g/l), the modified nano-adsorbent absorbed 73% of the methyl orange (MO) dye. Adsorption isotherm studies and kinetic model showed that the pseudo-second-order model and Langmuir equation agree with the obtained results. After three reductions of the modified nano-adsorbent in the photo-Fenton process, the dye absorption percentage was 69.50%.

Ultrasonic Functionalized Egg Shell Powder for the Adsorption of Cationic Dye: Equilibrium and Kinetic Studies

The present research focuses on synthesizing surface-modified egg shell powders using ultrasonic modification method for the effective adsorption of malachite green dye (MG). The presence of functional groups and surface morphology of ultrasonic-assisted egg shell powder (UAESP) was characterized using Fourier transform infrared spectrophotometer (FTIR) and scanning electron microscopy (SEM) analysis, respectively. A batch adsorption study was performed to predict the optimum conditions, and the results showed that maximum adsorption rate at the solution pH of 8.0 within the interaction time of 90 min, dosage of 1.5 g/L for MG dye concentration of 25 mg/L, and temperature 30°C. The isotherm and kinetics modeling of the present adsorption system can be well described by Freundlich and pseudosecond-order kinetics, respectively. The monolayer adsorption capacity of UAESP for MG dye was originated to be 64.58 mg/g. The results of the thermodynamic study reported that adsorption removal of MG dye onto UAESP was exothermic and spontaneous. This study accredited that UAESP has higher efficiency, cost-effective, and sustainable adsorbent for the removal of hazardous dyes on an industrial level.

Comparative studies on adsorptive and photocatalytic potential of differently synthesized ferric oxide nanoparticles for malachite green

In the present work, effect of different fuels on the structural, morphological, magnetic, adsorptive and photocatalytic properties of ferric oxide nanoparticles (Fe₂O₃ NPs) was evaluated. Fe₂O₃ NPs were synthesized via combustion method by using oxalyl dihydrazide (ODH), polyethylene glycol (PEG) and urea as fuels. The indigenously synthesized NPs were characterized by different analytical tools. XRD patterns confirmed the presence of α- and γ-Fe₂O₃ phases. TEM micrographs displayed average particle size was less than 30 nm. Saturation magnetization amplified with increase in the γ-Fe₂O₃ content, which was correlated to the fuel used for synthesis. Adsorptive and photocatalytic activity of synthesized NPs was studied using malachite green (MG) dye as a model compound. The uptake behavior for MG dye was influenced by the solution pH, contact time, adsorbent dose, temperature and dye concentration. Thermodynamic studies indicated the endothermic nature of the adsorption phenomenon. The adsorption was well defined with Langmuir and Freundlich isotherms in comparison to Dubinin-Radushkevitch adsorption isotherm model. The trend for percentage removal of MG dye using NPs synthesized by different fuels was: urea > PEG > ODH. Fe₂O₃ NPs facilitated photo degradation of dye solution in ultra-violet and visible light irradiations.

Graphene oxide decorated with cellulose and copper nanoparticle as an efficient adsorbent for the removal of malachite green

In this study, the graphene oxide surface was modified by grafting of nanocellulose and copper nanoparticles to promote the surface charge and adsorption efficiency for malachite green (MG). The structural and configurational properties of GO-CEL-Cu were verified by UV/Vis, SEM, TEM, EDX and FTIR spectroscopy and confirmed the electrostatic interaction and hydrogen bonding between GO, CEL and Cu-NPs. TEM images confirmed the deposition of Cu-NPs size between 24 and 37 nm on the GO surface. The uniform fine particles size makes strong interfacial interaction with GO sheets result in efficient load transfer from the matrix to the hybrid. The variable parameters such as adsorbent amount, MG concentration, pH, time and temperature were investigated to achieve optimum experimental condition. The experimental data was justified by Langmuir isotherm model with adsorption capacity for GO, GO-Cu, GO-CEL, GO-CEL-Cu as 127.3, 149.2, 156.8 and 207.1 mg/g, respectively. The spontaneity and endothermic nature of the process were confirmed by negative Gibbs free energy and followed the pseudo-second-order rate equation. Additionally, positive values of enthalpy and entropy suggesting endothermic process and increase randomness during process, respectively. In conclusion, nanocomposite is capable to adsorb the toxic dye due to its well economic, eco-friendly, well adsorption rate and regeneration ability.

Thermally reduced graphene oxide as green and easily available adsorbent for Sunset yellow decontamination

The release of synthetic food dyes, like Sunset yellow, into industrial effluents can cause serious environmental and health problems. Due to its aromatic structure, it is recalcitrant towards degradation into non-toxic intermediates and its removal by efficient adsorption represents a cheap and efficient method. Herein we propose the use of thermally reduced graphene oxide (TRGO) as effective Sunset yellow dye adsorbent with an adsorption maximum capacity comparable with other sophisticated, chemically synthesized carbon-based nanomaterials. The reduced graphene oxide and the Sunset yellow adsorbed one were characterized by FT-IR, XPS and XRD spectroscopy, N₂ adsorption-desorption isotherm and TGA analysis. BET surface area reduced from 274.1 m²/g (for TRGO) to 39.9 m²/g (for TRGO-SY) showing that Sunset Yellow molecules occupied the corresponding active sites while the number of sheets resulted from the XRD spectra - from 3 to 8 in TRGO to 5 in TRGO-SY indicates the ordered intercalations in the graphene structure. The adsorption isotherm experimental data were better fitted with the Langmuir model than the Freundlich model, with the maximum adsorption capacity of the SY dye monolayer of 243.3 mg/g at pH = 6.0 and 189.0 mg/g from synthetic wastewater. The kinetic study revealed a perfect fit following the Pseudo-second order model with an equilibrium achieved within 30 min. The lack of adsorption on the starting graphene oxide is indicative for π-π interactions between the adsorbate and adsorbent.

Gamma radiation as a green method to enhance the dielectric behaviour, magnetization, antibacterial activity and dye removal capacity of Co–Fe LDH nanosheets

Nowadays, improving the physico-chemical properties of nanomaterials to enhance their performance towards various applications is urgent. Accordingly, gamma irradiation (GI) has evolved and attracted wide attention as a promising green technique to meet this need. In the current study, a Co–Fe LDH was used as a model 2D nanomaterial and was irradiated by GI (dose = 100 kGy). The sample was characterized via XRD, FTIR, FESEM, HRTEM, hydrodynamic size, zeta potential, and BET surface area measurements. The results showed that after irradiation, the surface area of the sample increased from 83 to 89 m² g⁻¹. Moreover, irradiation increased its dielectric constant, dielectric loss and AC conductivity. In addition, the sample showed superparamagnetic behavior, where its saturation magnetization increased from 1.28 to 52.04 emu g⁻¹ after irradiation. Furthermore, the adsorption capacity of the irradiated LDH towards malachite green (MG) and methylene blue (MB) as model wastewater pollutants was also studied. The exposure of LDH to GI enhanced its adsorption capacity for MG from 44.73 to 54.43 mg g⁻¹. The Langmuir–Freundlich, Sips, and Baudu models were well suited for both MG and MB adsorption among the six fitted isotherm models. The pseudo-first and second order models fit the adsorption kinetics better than the intraparticle diffusion model for both dyes. The interaction of MB and MG with the LDH surface was further investigated in dry and aqueous solution using Grand canonical Monte Carlo and molecular dynamics simulations. These two techniques provided insight into the adsorption mechanism, which is vital to understand the adsorption process by the LDH nanosheets and their possible use in practical applications. Moreover, the Co–Fe LDH showed good antibacterial activity against both Gram-positive and Gram-negative bacteria strains. Furthermore, due to its magnetic property, the Co–Fe LDH could be simply recovered from water by magnetic separation at a low magnetic field after the adsorption process.

Nowadays, improving the physico-chemical properties of nanomaterials to enhance their performance towards various applications is urgent.

Facile synthesis of carbon-coated layered double hydroxide and its comparative characterisation with Zn-Al LDH: application on crystal violet and malachite green dye adsorption-isotherm, kinetics and Box-Behnken design

The adsorption of crystal violet (CV) and malachite green (MG) dyes using carbon-coated Zn-Al-layered double hydroxide (C-Zn-Al LDH) was investigated in this work. The characterisation of both Zn-Al LDH and C-Zn-Al LDH was performed using XRD, SEM, TEM, EDX, XPS, FTIR, BET and TGA. The results indicated that carbon particles were effectively coated on Zn-Al LDH surface. The average total pore volume and pore diameter of C-Zn-Al LDH were observed as 0.007 cc/g and 3.115 nm. The impact of parameters like initial dye concentration, pH and adsorbent dosage on the dye removal efficiency was confirmed by carrying out Box-Behnken design experiments. Langmuir isotherm was well suited for both CV and MG adsorption among other isotherm models. The adsorption capacity was maximally obtained as 129.87 and 126.58 mg/g for CV and MG respectively. Pseudo-second order fits the adsorption kinetics than any other kinetic models for both the dyes. The thermodynamic study indicates that the adsorption process of CV was exothermic, whereas for MG was endothermic. Electrostatic attraction, H-bonding, n-π and π- π interactions were mainly influenced in the adsorption process. This study concludes that C-Zn-Al LDH is an efficient adsorbent for the CV and MG dye removal from aqueous solutions. Graphical abstract ᅟ Graphical abstract contains text below the minimum required font size of 6pts inside the artwork, and there is no sufficient space available for the text to be enlarged. Please provide replacement figure file.Graphical abstract contains text is rewritten with the maximum required font size inside the artwork and provided sufficient space between the text which is enlarged.The new Graphical abstract is attached as an image in the attachment file for your further usage.

Isotherms and kinetic study of ultrasound-assisted adsorption of malachite green and Pb2+ ions from aqueous samples by copper sulfide nanorods loaded on activated carbon: Experimental design optimization

Copper sulfide nanorods loaded on activated carbon (CuS-NRs-AC) was synthesized and used for simultaneous ultrasound-assisted adsorption of malachite green (MG) and Pb²⁺ ions from aqueous solution. Following characterization of CuS-NRs-AC were investigated by SEM, EDX, TEM and XRD, the effects of pH (2.0-10), amount of adsorbent (0.003-0.011g), MG concentration (5-25mgL^-1), Pb²⁺ concentration (3-15mgL^-1) and sonication time (1.5-7.5min) and their interactions on responses were investigated by central composite design (CCD) and response surface methodology. According to desirability function on the Design Expert optimum removal (99.4%±1.0 for MG and 68.3±1.8 for Pb²⁺ions) was obtained at pH 6.0, 0.009g CuS-NRs-AC, 6.0min mixing by sonication and 15 and 6mgL^-1 for MG and Pb²⁺ ions, respectively. High determination coefficient (R²>0.995), Pred-R²-value (>0.920) and Adju-R²-value (>0.985) all are good indication of best agreement between the experimental and design modelling. The adsorption kinetics follows the pseudo-second order model and adsorption isotherm follows the Langmuir model with maximum adsorption capacity of 145.98 and 47.892mgg^-1 for MG and Pb²⁺ ions, respectively. This adsorbent over short contact time is good choice for simultaneous removal of large content of both MG and Pb²⁺ ions from wastewater sample.

Improved adsorption performance of nanostructured composite by ultrasonic wave: Optimization through response surface methodology, isotherm and kinetic studies

In this work, ultrasound-assisted adsorption of an anionic dye, sunset yellow (SY) and cationic dyes, malachite green (MG), methylene blue (MB) and their ternary dye solutions onto Cu@ Mn-ZnS-NPs-AC from water aqueous was optimized by response surface methodology (RSM) using the central composite design (CCD). The adsorbent was characterized using Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX) and EDX mapping images. The effects of various parameters such as pH, sonication time, adsorbent mass and initial concentrations of SY, MG and MB were examined. A total 33 experiments were conducted to establish a quadratic model. Cu@ Mn-ZnS-NPs-AC has the maximum adsorption efficiency (>99.5%) when the pH, sonication time, adsorbent mass and initial concentrations of SY, MG and MB were optimally set as 6.0, 5min, 0.02g, 9, 12 and 12mgL^-1, respectively. Sonication time has a statistically significant effect on the selected responses. Langmuir isotherm model was found to be best fitted to adsorption and adsorption capacities were 67.5mgg^-1 for SY, 74.6mgg^-1 for MG and 72.9mgg^-1 for MB. Four kinetic models (pseudo-first order, pseudo-second order, Weber-Morris intraparticle diffusion rate and Elovich) were tested to correlate the experimental data and the sorption was fitted well with the pseudo-second order kinetic model.

Single and multi-component adsorption of psychiatric pharmaceuticals onto alternative and commercial carbons

This work describes the adsorptive removal of three widely consumed psychiatric pharmaceuticals (carbamazepine, paroxetine and oxazepam) from ultrapure water. Two different adsorbents were used: a commercial activated carbon and a non-activated waste-based carbon (PS800-150-HCl), produced by pyrolysis of primary paper mill sludge. These adsorbents were used in single, binary and ternary batch experiments in order to determine the adsorption kinetics and equilibrium isotherms of the considered pharmaceuticals. For the three drugs and both carbons, the equilibrium was quickly attained (with maximum equilibrium times of 15 and 120 min for the waste-based and the commercial carbons, respectively) even in binary and ternary systems. Single component equilibrium data were adequately described by the Langmuir model, with the commercial carbon registering higher maximum adsorption capacities (between 272 ± 10 and 493 ± 12 μmol g^-1) than PS800-150-HCl (between 64 ± 2 and 74 ± 1 μmol g^-1). Multi-component equilibrium data were also best fitted by the single component Langmuir isotherm, followed by the Langmuir competitive model. Overall, competitive effects did not largely affect the performance of both adsorbents. Binary and ternary systems maintained fast kinetics, the individual maximum adsorption capacities were not lower than half of the single component systems and both carbons presented improved total adsorption capacities for multi-component solutions.

Removal of synthetic dyes from multicomponent industrial wastewaters

Colored effluents containing dyes from various industries pollute the environment and pose problems in municipal wastewater treatment systems. Industrial effluents consist of a mixture of dyes and require study of the simultaneous removal of dyes. Simultaneous quantification of dyes in the solution is a common problem while using a spectrophotometric method due to overlapping of their absorption spectra. Derivative spectroscopy and chemometric methods in spectrophotometric analysis facilitate simultaneous quantification of dyes. Adsorption is a widely used treatment method for the removal of a mixture of recalcitrant dyes in industrial wastewaters. Confirming the assertion, this paper presents a state-of-the-art review on methods used for simultaneous quantification of dyes and the effects of various parameters on their adsorptive removal. This paper also reviews the adsorption equilibrium, modeling, mechanisms of dyes adsorption, and adsorbent regeneration techniques in multicomponent dye systems. It has been observed that chemometric techniques provide accuracy, repeatability, and high speed in processing and helps in better operability in real wastewater treatment plants. The conclusions include the need for the development of thermodynamic models that can predict simultaneous physisorption and chemisorption exhibited by different dyes and to develop isotherm models that can describe chemisorption of a mixture of dyes. The paper delves into inadequately researched gray areas of adsorption of a mixture of dyes which require the development of modified adsorption methods that serves process intensification for complete degradation/mineralization.

Computation of adsorption parameters for the removal of dye from wastewater by microwave assisted sawdust: Theoretical and experimental analysis

In this research, the microwave assistance has been employed for the preparation of novel material from agro/natural bio-waste i.e. sawdust, for the effective removal of methylene blue (MB) dye from aqueous solution. The characterization of the newly prepared microwave assisted sawdust (MASD) material was performed by using FTIR, SEM and XRD analyses. In order to obtain the maximum removal of MB dye from wastewater, the adsorption experimental parameters such as initial dye concentration, contact time, solution pH and adsorbent dosage were optimized by trial and error approach. The obtained experimental results were applied to the different theoretical models to predict the system behaviour. The optimum conditions for the maximum removal MB dye from aqueous solution for an initial MB dye concentration of 25mg/L was calculated as: adsorbent dose of 3g/L, contact time of 90min, solution pH of 7.0 and at the temperature of 30°C. Freundlich and pseudo-second order models was best obeyed with the studied experimental data. Langmuir maximum monolayer adsorption capacity of MASD for MB dye removal was calculated as 58.14mg of MB dye/g of MASD. Adsorption diffusion model stated that the present adsorption system was controlled by intraparticle diffusion model. The obtained results proposed that, novel MASD was considered to be an effective and low-cost adsorbent material for the removal of dye from wastewater.

Screening and optimization of highly effective ultrasound-assisted simultaneous adsorption of cationic dyes onto Mn-doped Fe3O4-nanoparticle-loaded activated carbon

The ultrasound-assisted simultaneous adsorption of brilliant green (BG) and malachite green (MG) onto Mn-doped Fe₃O₄ nanoparticle-loaded activated carbon (Mn-Fe₃O₄-NP-AC) as a novel adsorbent was investigated and analyzed using first derivative spectrophotometry. The adsorbent was characterized using FT-IR, FE-SEM, EDX and XRD. Plackett-Burman design was applied to reduce the total number of experiments and to optimize the ultrasound-assisted simultaneous adsorption procedure, where pH, adsorbent mass and sonication time (among six tested variables) were identified as the most significant factors. The effects of significant variables were further evaluated by a central composite design under response surface methodology. The significance of independent variables and their interactions was investigated by means of the analysis of variance (ANOVA) within 95% confidence level together with Pareto chart. Using this statistical tool, the optimized ultrasound-assisted simultaneous removal of basic dyes was obtained at 7.0, 0.02g, 3min for pH, adsorbent mass, and ultrasonication time, respectively. The maximum values of BG and MG uptake under these experimental conditions were found to be 99.50 and 99.00%, respectively. The adsorption process was found to be followed by the Langmuir isotherm and pseudo-second order model using equilibrium and kinetic studies, respectively. According to Langmuir isotherm model, the maximum adsorption capacities of the adsorbent were obtained to be 101.215 and 87.566mgg^-1 for MG and BG, respectively. The value of apparent energy of adsorption obtained from non-linear Dubinin-Radushkevich model (4.348 and 4.337kJmol^-1 for MG and BG, respectively) suggested the physical adsorption of the dyes. The studies on the well regenerability of the adsorbent in addition to its high adsorption capacity make it promising for such adsorption applications.

Comparative study on ultrasonic assisted adsorption of dyes from single system onto Fe3O4 magnetite nanoparticles loaded on activated carbon: Experimental design methodology

The present study the ultrasound assisted adsorption of dyes in single system onto Fe₃O₄ magnetite nanoparticles loaded on activated carbon (Fe₃O₄-MNPs-AC) was described following characterization and identification of this adsorbent by conventional techniques likes field emission scanning electron microscopy, transmission electron microscopy, particle-size distribution, X-ray diffraction and Fourier transform infrared spectroscopy. A central composite design in conjunction with a response surface methodology according to f-test and t-test for recognition and judgment about significant term led to construction of quadratic model which represent relation among responses and effective terms. This model has unique ability to predict adsorption data behavior over a large space around central and optimum point. Accordingly Optimum conditions for well and quantitative removal of present dyes was obtained best operation and conditions: initial SY, MB and EB dyes concentration of 15, 15 and 25mgL^-1, 4.0, 6.0 and 5.0 of pH, 360, 360 and 240s sonication time and 0.04, 0.03 and 0.032g of Fe₃O₄-MNPs-AC. Replication of similar experiment (N=5) guide that average removal percentage of SY, MB and EB were found to be 96.63±2.86%, 98.12±1.67% and 99.65±1.21% respectively. Good agreement and closeness of Predicted and experimental result and high adsorption capacity of dyes in short time strongly confirm high suitability of present method for waste water treatment, while easy separation of present nanoparticle and its good regeneration all support good applicability of Fe₃O₄-MNPs-AC for waste water treatment. The kinetic study can be represented by combination of pseudo second-order and intraparticle diffusion. The obtained maximum adsorption capacities correspond to Langmuir as best model for representation of experimental data correspond to dyes adsorption onto Fe₃O₄-MNPs-AC were 76.37, 78.76 and 102.00mgg^-1 for SY, MB and EB, respectively. In addition, the performance comparison of ultrasound-assisted, magnetic stirrer assisted and vortex assisted adsorption methods demonstrates that ultrasound is an effective and good choice for facilitation of adsorption process via. Compromise of simple and facile diffusion.

Superior adsorption performance for triphenylmethane dyes on 3D architectures assembled by ZnO nanosheets as thin as ∼1.5nm

The 3-dimensional hierarchical ZnO flower-like architectures have been synthesized in a Zn(Ac)2·2H2O-Na2SeO3-KBH4-pyridine solvothermal system at 100°C for 24h. The flower-like architecture is assembled from ZnO nanosheets with a thickness of ∼1.5nm, and the flower-like architecture specific surface area is 132m(2)/g. When the ZnO flower-like architecture is used as the adsorbent for acid fuschin (AF), malachite green (MG), basic fuchsin (BF), congo red (CR) and acid red (AR) in water, the adsorption capacities for AF, MG, BF, CR and AR are 7154.9, 2587.0, 1377.9, 85.0 and 38.0mg/g, respectively. Evidently, the as-obtained ZnO flower-like architectures show excellent adsorption performances for triphenylmethane dyes, and the adsorption capacity of 7154.9mg/g for AF is the highest of all adsorbents for dyes. The adsorption mechanism can be attributed to the electrostatic attraction and the formation of ion-association complex between triphenylmethane dyes and ZnO hierarchical flower-like architectures.

Ultrasonic enhancement of the simultaneous removal of quaternary toxic organic dyes by CuO nanoparticles loaded on activated carbon: Central composite design, kinetic and isotherm study

Copper oxide nanoparticles loaded on activated carbon (CuO-NPs-AC) were prepared and fully analyzed and characterized with FE-SEM, XRD and FT-IR. Subsequently, this novel material was used for simultaneous ultrasound-assisted adsorption of brilliant green (BG), auramine O (AO), methylene blue (MB) and eosin yellow (EY) dyes. Problems regard to dyes spectra overlap in quaternary solution of this dyes were omitted by derivative spectrophotometric method. The best pH in quaternary system was studied by using one at a time method to achieved maximum dyes removal percentage. Subsequently, sonication time, adsorbent dosage and initial dyes concentrations influence on dyes removal was optimized by central composite design (CCD) combined with desirability function approach (DFA). Desirability score of 0.978 show optimum conditions set at sonication time (4.2 min), adsorbent mass (0.029 g), initial dyes concentration (4.5 mg L(-1)). Under this optimum condition the removal percentage for MB, AO, EY and BG dyes 97.58, 94.66, 96.22 and 94.93, respectively. The adsorption rate well fitted by pseudo second-order while adsorption capacity according to the Langmuir model as best equilibrium isotherm model for BG, MB, AO and EY was 20.48, 21.26, 22.34 and 21.29 mg g(-1), respectively.

Flowerlike Cu2Te architectures constructed from ultrathin nanoflakes as superior dye adsorbents for wastewater treatment

Flowerlike architectures assembled from Cu₂Te nanoflakes have been synthesized using a hydrothermal reaction of Te, Cu foils, and KBH₄with H₂O in the presence of ethanol amine (EA) at 200 °C for 12 h.

Electron beam-induced formation of crystalline nanoparticle chains from amorphous cadmium hydroxide nanofibers

Quantum dots (QDs) and especially quantum dot arrays have been attracting tremendous attention due to their potential applications in various high-tech devices, including QD lasers, solar cells, single photon emitters, QD memories, etc. Here, a dendrimer-based approach for the controlled synthesis of ultra-thin amorphous cadmium hydroxide nanofibers was developed. The fragmentation of the obtained nanofibers in crystalline nanoparticle chains under the irradiation with electron beam was observed in both ambient and cryo-conditions. Based on the experimental results, a model for the formation of amorphous nanofibers, as well as their transformation in crystalline nanoparticle chains is proposed. We foresee that these properties of the nanofibers, combined with the possibility to convert cadmium hydroxide into CdX (X=O, S, Se, Te), could result in a new method for the preparation of 2D and 3D QDs-arrays with numerous potential applications in high performance devices.

Synthesis of ultralong NiSe nanobelts and their excellent adsorption properties towards malachite green in water

NiSe ultralong nanobelts were synthesized by a solvothermal reaction of Ni with Se and KBH₄ in ethylenediamine and subsequent annealing in Ar, ​and employed as adsorbent for the removal of malachite green in wastewater.

Kinetic and isotherm study of Sudan black B removal

In this research, the removal of Sudan black B (SBB) by cadmium hydroxide nanowires loaded on activated carbon is described. After optimizing the variables involved, Langmuir, Freundlich, Tempkin, and Dubinin-Radushkevich models were applied to fit the experimental data. The adsorbent correlation coefficient and error analysis indicated the applicability of Langmuir model for the interpretation of equilibrium data. Different kinetic models were applied to analyze the time evolution of removal data. It was found that low quantity of adsorbent (<0.03 g) is capable of removal of large amount of SBB in reasonably short time (<40 min). The adsorption process was found to be described by both pseudo-second-order kinetics and interparticle diffusion mechanism. The effects of variables such as pH, amount of adsorbent, and contact time on batch adsorption process were investigated and optimized.