Synthesis of nickel sulfide nanoparticles loaded on activated carbon as a novel adsorbent for the competitive removal of Methylene blue and Safranin-O

Sustainable synthesis of magnetic Sargassum siliquastrum activated carbon loaded with NiS nanorods for adsorption of 2,4-D herbicide

The upgrade of sustainable resource waste into a valuable and beneficial material is an urgent task. The current paper outlines the development of an economical, sustainable, and prolonged adsorbent derived from Sargassum siliquastrum biomass and its use for potent 2,4-dichlorophenoxyacetic acid (2,4-D) removal. A simple carbonization approach was applied to obtain the highly functionalized carbon structure, which was subsequently transformed into a novel magnetic nanoadsorbent. The magnetic nanoadsorbent was characterized using Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), Brunauer Emmett Teller (BET)-specific surface area, and vibrating sample magnetometer (VSM). The characterization results confirm the successful formation of a high specific surface area and a uniform distribution of Fe3O4/NiS NPs grafted activated carbon. The adsorption kinetics was more accurately described via the pseudo-second order model; nevertheless, the isothermal data showed that the Langmuir model was most suitable. The monolayer adsorption capacity for 2,4-D was 208.26 ± 15.75 mg/g at 328 K. The favourability and spontaneity of the adsorption process were demonstrated by thermodynamic studies. The adsorbent displayed exceptional selectivity for 2,4-D and high stability in multi-cycle use. Electrostatic attraction, π-π stacking, and hydrogen bonding were all believed to have an impact on the sorbent's robust 2,4-D adsorption. Analyses of real tap and Nile River water samples showed little effect of the sample matrix on 2,4-D adsorption. This study presents an innovative approach for developing highly efficient adsorbent from natural biomass and offers an affordable way to recycle algal waste into beneficial materials.

UiO-66-NH2/guanidine-functionalized chitosan: A new bio-based reusable bifunctional adsorbent for removal of methylene blue from aqueous media

Methylene Blue (MB) is a common pollutant found in industrial wastewater, and its removal is crucial to ensure environmental sustainability. Due to MOFs have high surface area, tunable pore size distribution, and excellent adsorption capacity, in the current study, Uio-66-NH2@Cs-ISo-Gu nanohybrid was prepared through soluthermal method and then was used to remove MB dye. The results displayed that dye optimal adsorption by Uio-66-NH2@Cs-ISo-Gu nanohybrid occurred in the first 40 min, pH = 8, and low dye concentrations. Also, with increasing temperature, the amount of adsorption has decreased, which indicated the adsorption process would be exothermic. Based on the results, the Uio-66-NH2@Cs-ISo-Gu nanohybrid has a surface area of 120.9 m2.g-1 and a type IV isotherm. Also, the Freundlich isotherm and pseudo-second order models had the best agreement with the experimental data. The maximum adsorption capacity for this nanohybrid was 178.571, 153.846, and 135.135 mg.g-1 at 25 °C, 45 °C, and 65 °C temperatures, respectively, which could be successfully used as an excellent adsorbent in treatment of wastewater. However, further research is needed to understand the underlying adsorption mechanism and optimize the process for efficient removal of MB from contaminated water sources.

A Comprehensive Insight on Adsorption of Polyaromatic Hydrocarbons, Chemical Oxygen Demand, Pharmaceuticals, and Chemical Dyes in Wastewaters Using Biowaste Carbonaceous Adsorbents

Recent trends in adsorption of hazardous organic pollutants including Polyaromatic Hydrocarbons (PAHs), Chemical Oxygen Demand (COD), Pharmaceuticals, and Chemical Dyes in wastewater using carbonaceous materials such as activated carbon (AC) and biochar (BC) have been discussed in this paper. Utilization of biomass waste in the preparation of AC and BC has gained a lot of attention recently. This review outlines the techniques used for preparation, modification, characterization, and application of the above-mentioned materials in batch studies. The approaches towards understanding the adsorption mechanisms have also been discussed. It is observed that in the majority of the studies, high removal efficiencies were reported using biowaste adsorbents. Regarding the full potential of adsorption, varying values were obtained that are strongly influenced by the adsorbent preparation technique and adsorption method. In addition, most of the studies were concentrated on the kinetic, isotherm equilibrium, and thermodynamic aspects of adsorption, suggesting the dominant isotherm and kinetic models as Langmuir or Freundlich and pseudo-second-order models. Due to development in biosorbents, adsorption has been found to be increasingly economical. However, application of these adsorbents at commercial scale has not been adequately investigated and needs to be studied. Most of the studies have been conducted on synthetic solutions that do not completely represent the discharged effluents. This also needs attention in future studies.

Metal Sulfide Nanoparticles: Precursor Chemistry

Fascination with and the need for evermore increasing efficiency, power, or strength have been the cornerstones for developing new materials and methods for their creation. Higher solar cell conversion efficiencies, increased battery storage power, and lightweight strong materials are some that have been at the forefront of attention for these efforts. Materials created for most applications start as simple chemical compounds. A study of how these chemicals have been used in the past can be used to create new materials and new methods of production. Herein, a class of materials that are valuable in a multitude of applications, metal sulfide nanoparticles, are examined, along with how they are being produced and how new methods can be established that will help to standardize and increase production capabilities. Precursor–solvent combinations that can be used to create metal sulfide nanoparticles in the gas phase are also explored.

Synthesis and characterization of Cu(OH)2-NWs-PVA-AC Nano-composite and its use as an efficient adsorbent for removal of methylene blue

The present study focused on the synthesis of copper hydroxide nanowires decorated on activated carbon (Cu(OH)2-NWs-PVA-AC). The obtained Cu(OH)2-NWs-PVA-AC Nano-composite was distinguished by XRD, SEM, EDX, BET, FTIR and XPS respectively. Besides, different variables such as solution pH, and initial dye concentration, contact time, and temperature were performed on the adsorption efficiency of MB in a small batch reactor. Further, the experimental results are analyzed by various kinetic models via PFO, PSO, intra-particle diffusion and Elovich models, and the results revealed that among the kinetic models, PSO shows more suitability. In addition, different adsorption isotherms were applied to the obtained experimental data and found that Langmuir-Freundlich and Langmuir isotherm were best fits with the maximum adsorption capacity of 139.9 and 107.6 mg/g, respectively. The Nano-composite has outstanding MB removal efficiency of 94-98.5% with a span of 10 min. and decent adsorption of about 98.5% at a pH of 10. Thermodynamic constants like Gibbs free energy, entropy, and enthalpy were analyzed from the temperature reliance. The results reveal the adsorption processes are spontaneous and exothermic in nature. The high negative value of ΔG° (- 44.11 to - 48.86 kJ/mol) and a low negative value of ΔH° (- 28.96 kJ/mol) show the feasibility and exothermic nature of the adsorption process. The synthesized dye was found to be an efficient adsorbent for the potential removal of cationic dye (methylene blue) from wastewater within a short time.

Simultaneous removal of pollutants from water using nanoparticles: A shift from single pollutant control to multiple pollutant control

The steady increase in population, coupled with the rapid utilization of resources and continuous development of industry and agriculture has led to excess amounts of wastewater with changes in its composition, texture, complexity and toxicity due to the diverse range of pollutants being present in wastewater. The challenges faced by wastewater treatment today are mainly with the complexity of the wastewater as it complicates treatment processes by requiring a combination of technologies, thus resulting in longer treatment times and higher operational costs. Nanotechnology opens up a novel platform that is free from secondary pollution, inexpensive and an effective way to simultaneously remove multiple pollutants from wastewater. Currently, there are a number of studies that have presented a myriad of multi-purpose/multifunctional nanoparticles that simultaneously remove multiple pollutants in water. However, these studies have not been collated to review the direction that nanoparticle assisted wastewater treatment is heading towards. Hence, this critical review explores the feasibility and efficiency of simultaneous removal of co-existing/multiple pollutants in water using nanomaterials. The discussion begins with an introduction of different classes of pollutants and their toxicity followed by an overview and highlights of current research on multipollutant control in water using different nanomaterials as adsorbents, photocatalysts, disinfectants and microbicides. The analysis is concluded with a look at the current attempts being made towards commercialization of multipollutant control/multifunctional nanotechnology inventions. The review presents evidence of simultaneous removal of pathogenic microorganisms, inorganic and organic compound chemical pollutants using nanoparticles. Accordingly, not only is nanotechnology showcased as a promising and an environmentally-friendly way to solve the limitations of current and conventional centralised water and wastewater treatment facilities but is also presented as a good substitute or supplement in areas without those facilities.

Synthesis of biosurfactant‐coated magnesium oxide nanoparticles for methylene blue removal and selective Pb2+ sensing

Dyes and lead (Pb2+) are toxic compounds that can contaminant water. In this study, magnesium oxide (MgO) nanoparticles (NPs) prepared using clove, i.e. Syzygium aromaticum extract [clove extract (CE)] were used for methylene blue (MB) removal and Pb2+ ion sensing in aqueous solution. Maximum 90% MB removal was achieved using MgO NPs. The MB adsorption on MgO NPs surface followed second‐order kinetics and Langmuir isotherm. MB dye was adsorbed as a monolayer on the surface of MgO NPs with maximum adsorption capacity, 5555 mg g−1. MgO NPs were also able to selectively detect lead (Pb2+) in 1 nM–200 µM range with 24 µM (3σ) limit of detection. So, CE prepared MgO NPs are useful for MB dye adsorption and metal ion sensing applications.

Optimization of simultaneous ultrasound assisted toxic dyes adsorption conditions from single and multi-components using central composite design: Application of derivative spectrophotometry and evaluation of the kinetics and isotherms

Present study is devoted on the efficient application of Sn (O, S)-NPs -AC for simultaneous sonicated accelerated adsorption of some dyes from single and multi-components systems. Sn (O, S) nanoparticles characterization by FESEM, EDX, EDX mapping and XRD revel its nano size structure with high purity of good crystallinity. Present adsorbent due to its nano spherical shape particles with approximate diameter of 40-60nm seems to be highly effective in this regard. The effects of five variables viz. pH (3.5-9.5), 0.010-0.028g of adsorbent and 0.5-6.5min mixing by sonication is good and practical conditions for well and expected adsorption of MB and CV over concentration range of 3-15mgL^-1. Combination of response surface methodology (RSM) based on central composite design (CCD) and subsequent of analysis of variance (ANOVA) and t-test statistics were used to test the significance of the independent variables and their interactions. Regression analysis reveal that experimental data with high repeatability and efficiency well represented by second-order polynomial model with coefficient of determination value of 0.9988 and 0.9976 for MB and CV, respectively following conditions like pH 8.0, 0.016g adsorbent, 15mgL^-1 of both dyes 4min sonication time is proportional with achievement of experimental removal percentage of 99.80% of MB and 99.87% of CV in batch experiment. Evaluation and estimation of adsorption data with Langmuir and Freundlich isotherm well justify the results based on their correlation coefficient and error analysis confirm that Langmuir model is good model with adsorption capacity of 109.17 and 115.34mgg^-1 in single system and 95.69 and 102.99mgg^-1 in binary system for MB and CV, respectively. MB and CV kinetic and rate of adsorption well fitted by pseudo-second order equation both in single and binary systems and experimental results denote more and favorable adsorption of CV than respective value in single system. The pseudo-second-order rate constant k₂ in binary system larger than single system.

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.

Monocrystalline NiS nanowire arrays supported by Ni foam as binder-free electrodes with outstanding performances

Monocrystalline NiS nanowire arrays can achieve a higher areal capacitance of 8.7 F cm⁻² and excellent capacitance retention (78.7% after 8000 cycles).

Copper loaded on activated carbon as an efficient adsorbent for removal of methylene blue

Copper loaded activated carbon (Cu-AC) was prepared by impregnating it with cupric nitrate followed by microwave heating and then used for removing dyes in wastewater.

Adsorption of methylene blue from aqueous solution onto activated carbons developed from eucalyptus bark and Crataegus oxyacantha core

In this study, eucalyptus bark and Crataegus oxyacantha core-based activated carbon were synthesized and their morphological features characterized by scanning electron microscopy and Fourier transform infrared spectroscopy techniques. The efficiency of synthesized adsorbents in removal of methylene blue (MB) from aqueous solution was investigated in a series of batch experiments. Furthermore, the influences of various experimental factors involving the contact time, the initial dye concentration, the adsorbent dosage, and the pH of the dye solution were investigated. The point of zero charge (pH_pzc) of the applied adsorbents was also determined. In addition, the experimental data were expressed by Langmuir, Freundlich and Tempkin isotherms and pseudo-first order and pseudo-second order kinetic models. Adsorption equilibrium of the two adsorbents was reached within 1 h for MB concentrations of 20 to 100 mg/L. The equilibrium data obtained at optimum conditions of MB sorption by eucalyptus bark activated carbon and Crataegus oxyacantha core activated carbon were best fitted to Tempkin and Langmuir isotherm models, respectively. Besides, it was revealed that the adsorption rate follows a pseudo-second order kinetic model. From the findings of this study, it can be postulated that these adsorbents could be of great potential as a new class of adsorbents for organic dye removal from polluted water.

Synthesis of magnetic γ-Fe2O3-based nanomaterial for ultrasonic assisted dyes adsorption: Modeling and optimization

γ-Fe2O3 nanoparticles were synthesized and loaded on activated carbon. The prepared nanomaterial was characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The γ-Fe2O3 nanoparticle-loaded activated carbon (γ-Fe2O3-NPs-AC) was used as novel adsorbent for the ultrasonic-assisted removal of methylene blue (MB) and malachite green (MG). Response surface methodology and artificial neural network were applied to model and optimize the adsorption of the MB and MG in their individual and binary solutions followed by the investigation on adsorption isotherm and kinetics. The individual effects of parameters such as pH, mass of adsorbent, ultrasonication time as well as MB and MG concentrations in addition to the effects of their possible interactions on the adsorption process were investigated. The numerical optimization revealed that the optimum adsorption (>99.5% for each dye) is obtained at 0.02g, 15mgL(-1), 4min and 7.0 corresponding to the adsorbent mass, each dye concentration, sonication time and pH, respectively. The Freundlich, Langmuir, Temkin and Dubinin-Radushkevich isotherms were studied. The Langmuir was found to be most applicable isotherm which predicted maximum monolayer adsorption capacities of 195.55 and 207.04mgg(-1) for the adsorption of MB and MG, respectively. The pseudo-second order model was found to be applicable for the adsorption kinetics. Blank experiments (without any adsorbent) were run to investigate the possible degradation of the dyes studied in presence of ultrasonication. No dyes degradation was observed.

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.

Competitive removal of hazardous dyes from aqueous solution by MIL-68(Al): Derivative spectrophotometric method and response surface methodology approach

MIL-68(Al) as a metal-organic framework (MOF) was synthesized and characterized by different techniques such as SEM, BET, FTIR, and XRD analysis. This material was then applied for simulations removal of malachite green (MG) and methylene blue (MB) dyes from aqueous solutions using second order derivative spectrophotometric method (SODS) which was applied to resolve the overlap between the spectra of these dyes. The dependency of dyes removal efficiency in binary solutions was examined and optimized toward various parameters including initial dye concentration, pH of the solution, adsorbent dosage and ultrasonic contact time using central composite design (CCD) under response surface methodology (RSM) approach. The optimized experimental conditions were set as pH7.78, contact time 5min, initial MB concentration 22mgL(-1), initial MG concentration 12mgL(-1) and adsorbent dosage 0.0055g. The equilibrium data was fitted to isotherm models such as Langmuir, Freundlich and Tempkin and the results revealed the suitability of the Langmuir model. The maximum adsorption capacity of 666.67 and 153.85mgg(-1) was obtained for MB and MG removal respectively. Kinetics data fitting to pseudo-first order, pseudo-second order and Elovich models confirmed the applicability of pseudo-second order kinetic model for description of the mechanism and adsorption rate. Dye-loaded MIL-68(Al) can be easily regenerated using methanol and applied for three frequent sorption/desorption cycles with high performance. The impact of ionic strength on removal percentage of both dyes in binary mixture was studied by using NaCl and KCl soluble salts at different concentrations. According to our findings, only small dosage of the proposed MOF is considerably capable to remove large amounts of dyes at room temperature and in very short time that is a big advantage of MIL-68(Al) as a promising adsorbent for adsorptive removal processes.

Simultaneous and rapid dye removal in the presence of ultrasound waves and a nano structured material: experimental design methodology, equilibrium and kinetics

Tin sulfide nanoparticles loaded on activated carbon (SnS-AC) were prepared and characterized by FE-SEM, XRD, FT-IR and EDX.

Highly efficient simultaneous ultrasonic-assisted adsorption of methylene blue and rhodamine B onto metal organic framework MIL-68(Al): central composite design optimization

In this work, metal organic framework (MIL-68(Al)), was synthesized by a simple, fast and low-cost process for simultaneous removal of methylene blue and Rhodamine B, regarded to be toxic and even carcinogenic, from aqueous solution.

Synthesis, characterization and application of cyclam-modified magnetic SBA-15 as a novel sorbent and its optimization by central composite design for adsorption and determination of trace amounts of lead ions

A new, efficient, selective and relatively low cost adsorbent was developed based on Fe₃O₄@cyclam-SBA-15 for adsorption and determination of lead ions.

Statistical experimental design, least squares-support vector machine (LS-SVM) and artificial neural network (ANN) methods for modeling the facilitated adsorption of methylene blue dye

This study is based on the usage of a composite of zinc sulfide nanoparticles with activated carbon (ZnS-NPs-AC) for the adsorption of methylene blue (MB) from aqueous solutions.

SnO2 nanoparticle-loaded activated carbon for simultaneous removal of Acid Yellow 41 and Sunset Yellow; derivative spectrophotometric, artificial neural network and optimization approach

The simultaneous adsorption of Acid Yellow 41 (AY41) and Sunset Yellow (SY) onto SnO2 nanoparticle-loaded activated carbon (SnO2-NP-AC with very high BET surface area of 1278.71 m(2) g(-1)) was investigated. To overcome the severe dyes spectral overlapping, derivative spectrophotometric method and principal component analysis-artificial neural network (PCA-ANN) were successfully applied for the simultaneous determination of AY41 and SY in their binary solutions. By using central composite design (CCD) under response surface methodology, the effects of variables such as contact time, adsorbent dosage, pH, AY41 concentration and SY concentration on responses such as binary dyes removal percentages were examined. Optimal values were found to be 17.9 min, 0.024 g, 3.1, and 15.9 mg L(-1) and 18.7 mg L(-1), respectively. In binary solutions, the best fit to modified-extended Langmuir isotherm was obtained for the whole concentration range. In binary solutions, a synergism was observed for the AY41 and SY dyes adsorption onto SnO2-NP-AC. The adsorption rates at various times were analyzed. It indicated a pseudo-second-order kinetic model for the adsorption of both dyes.

EDTA-Cross-Linked β-Cyclodextrin: An Environmentally Friendly Bifunctional Adsorbent for Simultaneous Adsorption of Metals and Cationic Dyes

The discharge of metals and dyes poses a serious threat to public health and the environment. What is worse, these two hazardous pollutants are often found to coexist in industrial wastewaters, making the treatment more challenging. Herein, we report an EDTA-cross-linked β-cyclodextrin (EDTA-β-CD) bifunctional adsorbent, which was fabricated by an easy and green approach through the polycondensation reaction of β-cyclodextrin with EDTA as a cross-linker, for simultaneous adsorption of metals and dyes. In this setting, cyclodextrin cavities are expected to capture dye molecules through the formation of inclusion complexes and EDTA units as the adsorption sites for metals. The adsorbent was characterized by FT-IR, elemental analysis, SEM, EDX, ζ-potential, and TGA. In a monocomponent system, the adsorption behaviors showed a monolayer adsorption capacity of 1.241 and 1.106 mmol g(-1) for Cu(II) and Cd(II), respectively, and a heterogeneous adsorption capacity of 0.262, 0.169, and 0.280 mmol g(-1) for Methylene Blue, Safranin O, and Crystal Violet, respectively. Interestingly, the Cu(II)-dye binary experiments showed adsorption enhancement of Cu(II), but no significant effect on dyes. The simultaneous adsorption mechanism was further confirmed by FT-IR, thermodynamic study, and elemental mapping. Overall, its facile and green fabrication, efficient sorption performance, and excellent reusability indicate that EDTA-β-CD has potential for practical applications in integrative and efficient treatment of coexistenting toxic pollutants.

Optimization and modelling of synthetic azo dye wastewater treatment using Graphene oxide nanoplatelets: Characterization toxicity evaluation and optimization using Artificial Neural Network

Azo dyes pose a major threat to current civilization by appearing in almost all streams of wastewater. The present investigation was carried out to examine the potential of Graphene oxide (GO) nanoplatelets as an efficient, cost-effective and non-toxic azo dye adsorbent for efficient wastewater treatment. The treatment process was optimized using Artificial Neural Network for maximum percentage dye removal and evaluated in terms of varying operational parameters, process kinetics and thermodynamics. A brief toxicity assay was also designed using fresh water snail Bellamya benghalensis to analyze the quality of the treated solution. 97.78% removal of safranin dye was obtained using GO as adsorbent. Characterization of GO nanoplatelets (using SEM, TEM, AFM and FTIR) reported the changes in its structure as well as surface morphology before and after use and explained its prospective as a good and environmentally benign adsorbent in very low quantities. The data recorded when subjected to different isotherms best fitted the Temkin isotherm. Further analysis revealed the process to be endothermic and chemisorption in nature. The verdict of the toxicity assay rendered the treated permeate as biologically safe for discharge or reuse in industrial and domestic purposes.

Simultaneous ultrasound-assisted ternary adsorption of dyes onto copper-doped zinc sulfide nanoparticles loaded on activated carbon: optimization by response surface methodology

The simultaneous and competitive ultrasound-assisted removal of Auramine-O (AO), Erythrosine (Er) and Methylene Blue (MB) from aqueous solutions were rapidly performed onto copper-doped zinc sulfide nanoparticles loaded on activated carbon (ZnS:Cu-NP-AC). ZnS:Cu nanoparticles were studied by FESEM, XRD and TEM. First, the effect of pH was optimized in a one-at-a-time procedure. Then the dependency of dyes removal percentage in their ternary solution on the level and magnitude of variables such as sonication time, initial dyes concentrations and adsorbent dosage was fully investigated and optimized by central composite design (CCD) under response surface methodology (RSM) as well as by regarding desirability function (DF) as a good and general criterion. The good agreement found between experimental and predicted values supports and confirms the suitability of the present model to predict adsorption state. The applied ultrasound strongly enhanced mass transfer process and subsequently performance. Hence, a small amount of the adsorbent (0.04 g) was capable to remove high percentage of dyes, i.e. 100%, 99.6% and 100% for MB, AO and Er, respectively, in very short time (2.5 min). The experimental equilibrium data fitting to Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models showed that the Langmuir model applies well for the evaluation and description of the actual behavior of adsorption. The small amount of proposed adsorbent (0.015 g) was applicable for successful removal of dyes (RE>99.0%) in short time (2.5 min) with high adsorption capacity in single component system (123.5 mg g(-1) for MB, 123 mg g(-1) for AO and 84.5 mg g(-1) for Er). Kinetics evaluation of experiments at various time intervals reveals that adsorption processes can be well predicated and fitted by pseudo-second-order and Elovich models.

Adsorption behavior of direct red 80 and congo red onto activated carbon/surfactant: process optimization, kinetics and equilibrium

Adsorptions of congo red and direct red 80 onto activated carbon/surfactant from aqueous solution were optimized. The Box-Behnken design (BBD) has been employed to analyze the effects of concentration of surfactant, temperature, pH, and initial concentration of the dye in the adsorption capacity. Their corresponding experimental data could be evaluated excellently by second order polynomial regression models and the two models were also examined based on the analysis of variance and t test statistics, respectively. The optimum conditions were obtained as follows: Cs=34.10 μM, T=50°C, pH=3.5, and CCR=160 mg/L for the congo red system, and Cs=34.10 μM, T=50°C, pH=6.1, and CDR80=110 mg/L for the direct red 80 system. And in these conditions, the measured experimental maximum adsorption capacities for the congo red and direct red 80 removals were 769.48 mg/g and 519.90 mg/g, which were consistent with their corresponding predicted values, with small relative errors of -2.81% and -0.67%, respectively. The adsorption equilibrium and kinetics for the two dye adsorptions onto AC/DDAC were also investigated. The experimental data were fitted by four isotherm models, and Langmuir model presented the best fit. The kinetic studies indicated that the kinetic data followed the pseudo-second-order model.

Application of central composite design for simultaneous removal of methylene blue and Pb(2+) ions by walnut wood activated carbon

Activated carbon was prepared from walnut wood which was locally available, non-toxic, abundant and cheap. This new adsorbent was characterized using BET, FTIR and SEM. Point of zero charge (pHpzc) and oxygen containing functional groups were also determined. The prepared adsorbent was applied for simultaneous removal of Pb(2+) ions and methylene blue (MB) dye from aqueous solution. The prominent effect and interaction of variables such as amount of adsorbent, contact time, concentration of MB and Pb(2+) ions were optimized by central composite design. The equilibrium data obtained at optimum condition were fitted to conventional isotherm models and found that Langmuir model was the best fitted isotherm. Kinetic data were fitted using various models. It was revealed that the adsorption rate follows pseudo-second order kinetic model and intraparticle diffusion model.

Removal of basic dye Auramine-O by ZnS:Cu nanoparticles loaded on activated carbon: optimization of parameters using response surface methodology with central composite design

FESEM images of the prepared ZnS:Cu-NPs-AC.

Ternary dye adsorption onto MnO2 nanoparticle-loaded activated carbon: derivative spectrophotometry and modeling

MnO₂ nanoparticle-loaded activated carbon (MnO₂-NP-AC) as an efficient, environmental friendly and cost-effective adsorbent was synthesized and characterized using different techniques such as FE-SEM, EDX, XRD, BET and FTIR.