Highly efficient activation of periodate by a manganese-modified biochar to rapidly degrade methylene blue

In this study, the manganese oxide/biochar composites (Mn@BC) were synthesized from Phytolacca acinosa Roxb. The Mn@BC was analyzed via techniques of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction analysis (XRD). The results show that MnOx is successfully loaded on the surface of BC, and the load of MnOx can increase the number of surface functional groups of BC. X-ray photoelectron spectroscopy (XPS) shows that MnOx loaded on BC mainly exists in three valence forms: Mn(Ⅱ), Mn(Ⅲ), and Mn(Ⅳ). The ability of Mn@BC to activate periodate (PI) was studied by simulating the degradation of methylene blue (MB) dye. The degradation experiment results showed that the MB removal rate by the Mn@BC/PI system reached 97.4% within 30 min. The quenching experiment and electron paramagnetic resonance (EPR) analysis confirmed that Mn@BC can activate PI to produce iodate (IO3•), singlet oxygen (1O2), and hydroxyl radical (•OH), which can degrade MB during the reaction. Response surface methodology (RSM) based on Box-Behnken Design (BBD) was used to determine the interaction between pH, Mn@BC and PI concentration in the Mn@BC/PI system, and the optimum technological parameters were determined. When pH = 5.4, Mn@BC concentration 0.56 mg/L, PI concentration 1.1 mmol/L, MB removal rate can reach 98.05%. The cyclic experiments show that Mn@BC can be reused. After four consecutive runs, the removal rate of MB by the Mn@BC/PI system is still 82%, and the Mn@BC/PI system also shows high performance in treating MB in actual water bodies and degrading other pollutants. This study provides a practical method for degrading dyes in natural sewage.

Selective adsorption of anionic and cationic dyes on mesoporous UiO-66 synthesized using a template-free sonochemistry method: kinetic, isotherm and thermodynamic studies

In this study, template-free mesoporous UiO-66(U) has been successfully synthesized in shortened time by sonochemical methods and provided energy savings. The synthesized mesoporous UiO-66(U) demonstrated irregular morphology particle around 43.5 nm according to the SEM image. The N₂ adsorption-desorption isotherm indicated an irregular, 8.88 nm pore width mesoporous structure. Ultrasonic irradiation waves greatly altered mesoporous materials. A mechanism for mesoporous UiO-66(U) formation has been proposed based on the present findings. Sonochemical-solvent heat saves 97% more energy than solvothermal. Mesoporous UiO-66(U) outperformed solvothermal-synthesized UiO-66(S) in adsorption. These studies exhibited that mesopores in UiO-66 promote dye molecule mass transfer (MO, CR, and MB). According to kinetics and adsorption isotherms, the pseudo-second-order kinetic and Langmuir isotherm models matched experimental results. Thermodynamic studies demonstrated that dye adsorption is spontaneous and exothermically governed by entropy, not enthalpy. Mesoporous UiO-66(U) also showed good anionic dye selectivity in mixed dye adsorption. Mesoporous UiO-66(U) may be regenerated four times while maintaining strong adsorption capability.

Polymeric biomolecules based nanomaterials: Production strategies and pollutant mitigation as an emerging tool for environmental application

The ever-exploding global population coupled with its anthropogenic impact has imparted unparalleled detrimental effects on the environment and mitigating them has emerged as the prime challenge and focus of the current century. The niche of nanotechnology empowered by composites of biopolymers in the handling of xenobiotics and environmental clean-up has an unlimited scope. The appositeness of biopolymer-nanoparticles (Bp-NPs) for environmental contaminant mitigation has received unique consideration due to its exclusive combination of physicochemical characteristics and other attributes. The current review furnishes exhaustive scrutiny of the current accomplishments in the development of Bp-NPs and biopolymer nanomaterials (Bp-NMs) from various polymeric biomolecules. Special attention was provided for polymeric biomolecules such as cellulose, lignin, starch, chitin, and chitosan, whereas limited consideration on gelatin, alginate, and gum for the development of Bp-NPs and Bp-NMs; together with coverage of literature. Promising applications of tailored biopolymer hybrids such as Bp-NPs and Bp-NMs on environmentally hazardous xenobiotics handling and pollution management are discussed as to their notable environmental applications.

Surface-Enhanced Biocompatibility and Adsorption Capacity of a Zirconium Phosphate-Coated Polyaniline Composite

The present study deals with the synthesis, characterization, and testing of a novel composite, zirconium(IV) phosphate-coated polyaniline (ZrPO4@PANI), toward the adsorption- and surface-controlled toxicity applications. Following the synthesis of the ZrPO4@PANI composite using the sol-gel route, various characterization techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy, and powder X-ray diffraction were employed to confirm its surface functionality, morphology and agglomeration, and crystallinity and crystal nature, respectively. The composite was found to be effective toward the adsorptive removal of the methylene blue dye (an organic pollutant) as against the changes in the dye concentration, dose, pH, and so forth. Also, to understand the MB adsorption kinetics, the experimental data were evaluated using the Langmuir and Freundlich models and the results were described in accordance with the Langmuir isotherm model (an adsorption capacity of 120.48 mg/g at ambient temperature). In addition, the tests conducted using pseudo-first- and pseudo-second-order kinetic models confirmed the existence of pseudo-second-order rates. Furthermore, the calculation of thermodynamic parameters for the MB adsorption, namely, changes in enthalpy, entropy, and Gibbs' free energy, exhibited a spontaneous, feasible, and exothermic nature. Finally, the comparative studies of in vitro toxicity and flow cytometry confirmed that the copresence of ZrPO4 along with PANI significantly improved the biocompatibility. The outcome of the experimental results implies that the composite is capable enough of serving as the safe and low-cost adsorbent, in addition to supporting the effective capping of the surface toxicity of PANI.

Green synthesis and environmental application of iron-based nanomaterials and nanocomposite: A review

Green chemistry has been proven to be an efficient route for nanoparticle synthesis. Plant extract based green synthesis of various nanoparticles is extensively studied since the last decade. This paper "Green synthesis and environmental application of Iron-based nanomaterials and nanocomposite: A review" unveils all the possible greener techniques for the synthesis of iron-based nanoparticles and nanocomposites. The use of different plant sources, microorganisms, and various biocompatible green reagents such as biopolymers, cellulose, haemoglobin, and glucose for the synthesis of iron nanoparticles reported in the last decade are summarized. The microwave method, along with hydrothermal synthesis due to their lower energy consumption are also been referred to as a green route. Apart from different plant parts, waste leaves and roots used for the synthesis of iron nanoparticles are extensively briefed here. This review is thus compact in nature which covers all the broad areas of green synthesis of iron nanoparticles (NPs) and iron-based nanocomposites. Detailed discussion on environmental applications of the various green synthesized iron NPs and their composites with performance efficiency is provided in this review article. The advantages of bimetallic iron-based nanocomposites over iron NPs in various environmental applications are discussed in detail. The hazards and toxic properties of green synthesized iron-based NPs are compared with those obtained from chemical methods. The prospects and challenges section of this article provides a vivid outlook of adapting such useful technique into a more versatile process with certain inclusions which may encourage and provide a new direction to future research.

Ultrasound wave assisted removal of Ceftriaxone sodium in aqueous media with novel nano composite g-C3N4/MWCNT/Bi2WO6 based on CCD-RSM model

The aim of this study was ultrasound assisted removal of Ceftriaxone sodium (CS) based on CCD model. Using sonochemical synthesized Bi₂WO₆ implanted on graphitic carbon nitride/Multiwall carbon nanotube (g-C₃N₄/MWCNT/Bi₂WO₆). For this purpose g-C₃N₄/MWCNT/Bi₂WO₆ was synthesized and characterized using diverse approaches including XRD, FE-SEM, XPS, EDS, HRTEM, FT-IR. Then, the contribution of conventional variables including pH, CS concentration, adsorbent dosage and ultrasound contact time were studied by central composite design (CCD) under response surface methodology (RSM). ANOVA was employed to the variable factors, and the most desirable operational conditions mass provided. Drug adsorption yield of 98.85% obtained under these defined conditions. Through conducting five experiments, the proper prediction of the optimum point were examined. The respective results showed that RSD% was lower than 5% while the t-test confirmed the high quality of fitting. Langmuir isotherm equation fits the experimental data best and the removal followed pseudo-second order kinetics. The estimation of the experimentally obtained maximum adsorption capacities was 19.57 mg.g^- of g-C₃N₄/MWCNT/Bi₂WO₆ for CS. Boundary layer diffusion explained the mechanism of removal via intraparticle diffusion.

Synthesis of novel biocomposite powder for simultaneous removal of hazardous ciprofloxacin and methylene blue: Central composite design, kinetic and isotherm studies using Brouers-Sotolongo family models

Over the past decades, extensive efforts have been made to use biomass-based-materials for wastewater-treatment. The first purpose of this study was to develop and characterize regenerated-reed/reed-charcoal (RR-ChR), an enhanced biosorbent from Tunisian-reed (Phragmites-australis). The second aim was to assess and optimize the RR-ChR use for the removal of binary ciprofloxacin antibiotic (CIP) and methylene blue dye (MB), using Central Composite Design under Response Surface methodology. The third purpose was to explain the mechanisms involved in the biosorption-process. The study revealed that the highest removal-percentages (76.66 % for the CIP and 100 % for the MB) were obtained under optimum conditions: 1.55 g/L of adsorbent, 35 mg/L of CIP, 75 mg/L of MB, a pH of 10.42 and 115.28 min contact time. It showed that the CIP biosorption mechanism was described by Brouers-Sotolongo-fractal model, with regression-coefficient (R²) of 0.9994 and a Person's Chi-square (X²) of 0.01. The Hill kinetic model better described the MB biosorption (R² = 1 and X² = 1.0E-4). The isotherm studies showed that the adsorbent surface was heterogeneous and the best nonlinear-fit was obtained with the Jovanovich (R² = 0.9711), and Brouers-Sotolongo (R² = 0.9723) models, for the CIP and MB adsorption, respectively. Finally, the RR-ChR lignocellulosic-biocomposite-powder could be adopted as efficient and cost-effective adsorbent.

Adsorptive decontamination of wastewater containing methylene blue dye using golden trumpet tree bark (Handroanthus albus)

The golden trumpet tree bark (GTB), a wood-processing residue, was tested as adsorbent material for decontamination of wastewaters containing methylene blue dye (MB). The powdered material was preponderantly amorphous, containing an irregular surface with the presence of lignin and holocellulose. The adsorption was favorable at basic pH of 10 and adsorbent dosage of 0.5 g L^-1. The kinetics has finished in only 30 min and fitted by the general order model (GO). The isotherm behaviors were successfully represented by the Langmuir model. The value found for the maximum adsorption capacity was 232.25 mg g^-1, being obtained at 328 K. The standard variation of Gibbs free energy (ΔG⁰) ranged from - 10.77 to - 8.09 kJ mol^-1, indicating a spontaneous and favorable adsorption. A variation of standard enthalpy (ΔH⁰) of 18.58 kJ mol^-1 revealed an endothermic adsorption. A sloped forward curve was found in the continuous operation, with breakthrough time (t_b) of 325 min. The stoichiometry capacity of the column (q_eq) and the length of mass transfer zone (Z_m) were, respectively, 23.57 mg g^-1 and 11.28 cm. The GTB was efficient in the treatment of a simulated effluent, obtaining color removal of 96%. These results show that GTB can be applied as adsorbent for decontamination of wastewaters containing methylene blue.

A novel route for preparation of chemically activated carbon from pistachio wood for highly efficient Pb(II) sorption

Pistachio wood-derived activated carbon prepared by a two-stage process (PWAC-2), conducting two consecutive chemical activation processes with NH₄NO₃ and NaOH, respectively. The results showed that explosive characteristic of NH₄NO₃ can primarily be employed to produce a char, with a large surface area and a highly-ordered pore structure, which can be subjected to a second activation process with NaOH to prepare a more suitable activated carbon, with a highly porous structure and useful functional groups, for removal of lead ions from aqueous media. An L₂₅ Taguchi experimental design was used by varying impregnation ratio, activation time and temperature in both pre- and post-activation stages, and the results showed that, in both stages, a small activating agent/precursor and a proportional low activation time suffice for preparation of an advantageous activated carbon for Pb(II) adsorption. A comprehensive study was performed on the equilibrium, kinetic and thermodynamic aspects of Pb(II) adsorption by the new activated carbon. The results exhibited that, having had a high lead adsorption capacity (190.2 mg g^-1), a high adsorption rapidness, and thermodynamic favorability, PWAC-2 is a beneficial alternative for utilization in full-scale plants of lead removal from waters and wastewaters.

Valorization of Crataegus azarolus stones for the removal of textile anionic dye by central composite rotatable design using cubic model: optimization, isotherm, and kinetic studies

In this study, the central composite rotatable design (CCRD) was used in the optimization of the operating parameters for the removal of the direct blue 86 (DB86), an anionic dye, because of its hazardous impact on human health and aquatic environment. In addition, DB86 is a recalcitrant and non-biodegradable dye whose presence considerably inhibits photosynthesis. Its removal in aqueous medium was achieved by biosorption onto the novel biosorbent Crataegus azarolus stones (CAS). The parameters like the solution pH, biosorbent dose, initial DB86 concentration, and temperature were studied in the ranges 2-6, 0.8-4 g L^-1, 20-100 mg L^-1, and 10-50 °C, respectively. The significance of the experimental parameters and their interactions was investigated by the Student's t test and p values with 5% error limits using JMP 11.0.0 software. The regression analysis of the experimental data obtained from 31 batch runs provides a cubic model. The optimum conditions obtained for the maximum DB86 elimination from the synthetic solution were found to be pH 2, biosorbent dose of 4 g L^-1, initial DB86 concentration of 20 mg L^-1, and temperature of 10 °C, leading to a theoretical maximum removal of 123%. The experimental data were analyzed by the Langmuir, Freundlich, and Temkin equilibrium models. The Langmuir isotherm gave the best fit with a maximum biosorption capacity of 24.02 mg g^-1. The results of the kinetic study revealed that the biosorption kinetic of DB86 follows a pseudo-second-order model. All results confirmed that CAS are an efficient, economic, and ecological alternative for the treatment of industrial wastewaters loaded with anionic dyes.

Rapid and high-capacity ultrasonic assisted adsorption of ternary toxic anionic dyes onto MOF-5-activated carbon: Artificial neural networks, partial least squares, desirability function and isotherm and kinetic study

The present paper focused on the ultrasonic assisted simultaneous removal of fast green (FG), eosin Y (EY) and quinine yellow (QY) from aqueous media following using MOF-5 as a metal organic framework and activated carbon hybrid (AC-MOF-5). The structure and morphology of AC-MOF-5 was identified by SEM, FTIR and XRD analysis. The interactive and main effects of variables such as pH, initial dyes concentration (mgL^-1), adsorbent dosage (mg) and sonication time (min) on removal percentage were studied by central composite design (CCD), subsequent desirability function (DF) permit to achieved real variable experimental condition. Optimized values were found 7.06, 5.68, 7.59 and 5.04mgL^-1, 0.02g and 2.55min for pH, FG, EY and QY concentration, adsorbent dosage and sonication time, respectively. Under this conditions removal percentage were obtained 98.1%, 98.1% and 91.91% for FG, EY and QY, respectively. Two models, namely partial least squares (PLS) and multi-layer artificial neural network (ANN) model were used for building up to construct an empirical model to predict the dyes under study removal behavior. The obtained results show that ANN and PLS model is a powerful tool for prediction of under-study dyes adsorption by AC-MOF-5. The evaluation and estimation of equilibrium data from traditional isotherm models display that the Langmuir model indicated the best fit to the equilibrium data with maximum adsorption capacity of 21.230, 20.242 and 18.621mgg^-1, for FG, EY and QY, respectively, while the adsorption rate efficiently follows the pseudo-second-order model.

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.

Design and construction of nanoscale material for ultrasonic assisted adsorption of dyes: Application of derivative spectrophotometry and experimental design methodology

Response surface methodology (RSM) based on central rotatable experimental design was used to investigate the effect of ultrasound assisted simultaneous adsorption process variables on Cu: ZnS-NPs-AC from aqueous solution. Cu: ZnS-NPs-AC was characterized using field emission scanning electron microscopy (FE-SEM), Energy Dispersive X-ray Spectroscopy (EDX) and X-ray diffraction (XRD). To overcome the severe methylene blue (MB) and brilliant green (BG) dyes spectral overlapping, derivative spectrophotometric method were successfully applied for the simultaneous determination of dyes in their binary solutions. Simultaneous determination of the dyes can be carried out using the first-order and second order derivative signal at 664 and 663nm for BG and MB, respectively. The factors investigated were pH (2.5-8.5), adsorbent mass (0.006-0.030g), sonication time (1-5min) and initial MB and BG concentration (3-15mgL^-1). Five levels, which were low level, center point, upper level and two axillar points, were considered for each of the factors. The desirability function (DF: 0.9853) on the STATISTICA version 10.0 software showed that the optimum removal (99.832 and 99.423% for MB and BG, respectively) was obtained at pH 8.0, adsorbent mass 0.024g, sonication time 4min and 9mgL^-1 initial concentration for each dye. Besides, the results show that obtained data were adequately fitted into the second-order polynomial model, since the calculated model F value (172.96 and 96.35 for MB and BG, respectively) is higher than the critical F value. The values of coefficient of determination (0.9968 and 0.9943 for MB and BG, respectively) and adjusted coefficient of determination (0.9911 and 0.9840 for MB and BG, respectively) are close to 1, indicating a high correlation between the observed and the predicted values. The ultrasonic amplitude and adsorbent mass were found to be the most effective variable influencing the adsorption process. The adsorption equilibrium was well described by the Langmuir isotherm model with maximum adsorption capacity of 185.2 and 151.5mgg^-1 for MB and BG respectively on adsorbent. The results indicate that pseudo-second-order kinetic equation and intra-particle diffusion model can better describe the adsorption kinetics.

The performance of nanorods material as adsorbent for removal of azo dyes and heavy metal ions: Application of ultrasound wave, optimization and modeling

The present research is focused on the synthesis and characterization of zinc (II) oxide nanorods loaded on activated carbon (ZnO-NRs-AC) to prepare an outstanding adsorbent for the simultaneous adsorption of heavy metals and dyes as hazardous pollutant using ultrasound energy. The adsorbent was identified by Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. The individual effects and possible interactions between the most effective variables including initial metal ions (Cd²⁺ and Co²⁺) and azo dyes (methylene blue (MB) and crystal violet (CV)) concentration, adsorbent dosage and ultrasonic time on the responses were investigated by response surface methodology (RSM) and optimum conditions was fixed at Cd²⁺, Co²⁺, MB and CV concentrations were 25, 24, 18 and 14mgL^-1, respectively, 0.025g of ZnO-NRs-AC and 5.1min sonication to achieve maximum removal percentage (>97.0%) for targets compounds. The artificial neural network (ANN) model was applied for prediction of data with Levenberg-Marquardt algorithm (LMA), a linear transfer function (purelin) at output layer and a tangent sigmoid transfer function (tansig) in the hidden layer with 14 neurons. The minimum mean squared error (MSE) of 0.9646, 0.0402 and 0.0753 with high determination coefficient (R²) of 0.9996, 0.9991 and 0.9999 for train, test and validation, respectively, were able to predict and model the adsorption process. The results of examination of the time on experimental adsorption data and their subsequent fitting reveal applicability of pseudo-second-order and intraparticle diffusion model. The experimental equilibrium data was analyzed by Langmuir, Freundlich, Temkin and D-R isotherm models and explored that the data well presented by Langmuir model with maximum adsorption capacity of 97.1, 92.6, 83.9 and 81.6mgg^-1 for Cd⁺², Co⁺² ions, MB and CV dyes, respectively.

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.

Multi-response optimization of ultrasound assisted competitive adsorption of dyes onto Cu (OH)2-nanoparticle loaded activated carbon: Central composite design

This paper focuses on the development of an effective methodology to obtain the optimum removal conditions assisted by ultrasonics to maximize the simultaneous removal of dyes, eosin Y (EY), methylene blue (MB) and phenol red (PR), by Cu(OH)₂-NP-AC in aqueous solution using response surface methodology (RSM). The effects of variables such as pH, initial dyes concentrations (mgL^-1), and amount of sorbent (mg) and sonication time (min) on the dyes removal were studied. A central composite design (CCD) was applied to evaluate the interactive effects of adsorption variables. A good correlation (with R²>0.940) between the statistical model and experiment was found for dyes removal from aqueous wastewater using the adsorbent. The optimum removal (99.20%±1.48) was thus obtained at pH 6.0, ultrasound time 2.5min, adsorbent mass 20mg and initial dye concentration at 5mgL^-1 for MB and EY and 12.5mgL^-1 for PR. The maximum adsorption capacity (Q_max) was calculated from the Langmuir isotherm as 32.9, 26.4 and 38.5mgg^-1 for the MB, EY and PR, respectively for the 0.015g of sorbent. The adsorption kinetic data of the dyes were analyzed and was found fitting well in a pseudo-second-order equation. Adsorption isotherms and separation factors showed that the adsorbent displays a high selectivity toward one dye in a three-component system with an affinity order of PR>MB>EY. On the other hand, acoustic waves emitted by the cavitation bubbles render a direct effect on the process. This is attributed to the discrete nature and high pressure amplitude of the waves, which creates excessively high convection in the medium, causing adsorption of the pollutants. The chemical nature of the pollutants influences the enhancement effect of ultrasound.

Optimization of photocatalytic degradation of palm oil mill effluent in UV/ZnO system based on response surface methodology

This paper reports on the optimization of palm oil mill effluent (POME) degradation in a UV-activated-ZnO system based on central composite design (CCD) in response surface methodology (RSM). Three potential factors, viz. O₂ flowrate (A), ZnO loading (B) and initial concentration of POME (C) were evaluated for the significance analysis using a 2³ full factorial design before the optimization process. It is found that all the three main factors were significant, with contributions of 58.27% (A), 15.96% (B) and 13.85% (C), respectively, to the POME degradation. In addition, the interactions between the factors AB, AC and BC also have contributed 4.02%, 3.12% and 1.01% to the POME degradation. Subsequently, all the three factors were subjected to statistical central composite design (CCD) analysis. Quadratic models were developed and rigorously checked. A 3D-response surface was subsequently generated. Two successive validation experiments were carried out and the degradation achieved were 55.25 and 55.33%, contrasted with 52.45% for predicted degradation value.

Ultrasonic-assisted magnetic solid phase extraction of morphine in urine samples by new imprinted polymer-supported on MWCNT-Fe3O4-NPs: Central composite design optimization

Multiwalled carbon nanotubes (MWCNTs) were magnetized with Fe3O4 nanoparticles (MWCNTs-Fe3O4-NPs) and subsequently coated by vinyl end groups (Vinyltrimethoxysilane). MWCNT-Fe3O4-NPs were used as support for a new morphine (MO) molecularly imprinted polymer (MWCNT-Fe3O4-NPs@MO-MIP) by surface imprinting polymerization method. The MWCNT-Fe3O4-NPs@MO-MIP was characterized by FTIR, VSM and SEM techniques and successfully used for determination of MO. Ultrasonic-assisted magnetic solid phase extraction followed by UV-vis spectrophotometer (UAMSPE-UV-vis) was investigated for MWCNT-Fe3O4-NPs@MO-MIP and compared with non-imprinted polymer (NIP) using batch method. Central composite design under response surface methodology was used for the evaluation of the effect of variables, individually, as well as their possible interaction effects on the adsorption process. The variables such as sonication time, MWCNT-Fe3O4-NPs@MO-MIP mass, initial concentration of MO and pH were investigated in this study. At optimum experimental conditions, UAMSPE-UV-vis method was exhibited a linear range of 0.8-8.7mgL(-1) of the MO concentration with a detection limit of 0.18mgL(-1). The relative standard deviation for the analyte was found to be lower than 2.32%. The MWCNT-Fe3O4-NPs@MO-MIP adsorption capacity was found to be 37.01mgg(-1). The enrichment and preconcentration factors were found to be 107.01 and 98.21, respectively. The developed method was finally applied successfully to the determination of MO in urine and wastewater samples with the recoveries ranged from 96.40 to 105.6%.

Highly efficient ultrasonic-assisted removal of Hg(II) ions on graphene oxide modified with 2-pyridinecarboxaldehyde thiosemicarbazone: Adsorption isotherms and kinetics studies

A novel adsorbent, based on modifying graphene oxide (GO) chemically with 2-pyridinecarboxaldehyde thiosemicarbazone (2-PTSC) as ligand, was designed by facile process for removal of Hg(II) from aqueous solution. Characterization of the adsorbent was performed using various techniques, such as FT-IR, XRD, XPS, SEM and AFM analysis. The adsorption capacity was affected by variables such as adsorbent dosage, pH solution, Hg(2+) initial concentration and sonicating time. These variables were optimized by rotatable central composite design (CCD) under response surface methodology (RSM). The predictive model for Hg(II) adsorption was constructed and applied to find the best conditions at which the responses were maximized. In this conditions, the adsorption capacity of this adsorbent for Hg(2+) ions was calculated to be 309mgg(-1) that was higher than that of GO. Appling the ultrasound power combined with adsorption method was very efficient in shortening the removal time of Hg(2+) ions by enhancing the dispersion of adsorbent and metal ions in solution and effective interactions among them. The adsorption process was well described by second-order kinetic and Langmuir isotherm model in which the maximum adsorption capacity (Qm) was found to be 555mgg(-1) for adsorption of Hg(2+) ions over the obtained adsorbent. The performance of adsorbent was examined on the real wastewaters and confirmed the applicability of adsorbent for practical applications.

Application of ZnO nanorods loaded on activated carbon for ultrasonic assisted dyes removal: Experimental design and derivative spectrophotometry method

A method based on application of ZnO nanorods loaded on activated carbon (ZnO-NRs-AC) for adsorption of Bromocresol Green (BCG) and Eosin Y (EY) accelerated by ultrasound was described. The present material was synthesized under ultrasound assisted wet-chemical method and subsequently was characterized by FE-SEM, TEM, BET and XRD analysis. The extent of contribution of conventional variables like pH (2.0-10.0), BCG concentration (4-20mgL(-1)), EY concentration (3-23mgL(-1)), adsorbent dosage (0.01-0.03g), sonication time (1-5min) and centrifuge time (2-6min) as main and interaction part were investigated by central composite design under response surface methodology. Analysis of variance (ANOVA) was adapted to experimental data and guide the best operational conditions mass by set at 6.0, 9mgL(-1), 10mgL(-1), 0.02g, 4 and 4min for pH, BCG concentration, EY concentration, adsorbent dosage, sonication and centrifuge time, respectively. At these specified conditions dye adsorption efficiency was higher than 99.5%. The suitability and well prediction of optimum point was tested by conducting five experiments and respective results revel that RSD% was lower than 3% and high quality of fitting was confirmed by t-test. The experimental data were best fitted in Langmuir isotherm equation and the removal followed pseudo second order kinetics. The experimentally obtained maximum adsorption capacities were estimated as 57.80 and 61.73mgg(-1) of ZnO-NRs-AC for BCG and EY respectively from binary dye solutions. The mechanism of removal was explained by boundary layer diffusion via intraparticle diffusion.

Experimental design and modeling of ultrasound assisted simultaneous adsorption of cationic dyes onto ZnS: Mn-NPs-AC from binary mixture

The manganese impregnated zinc sulfide nanoparticles deposited on activated carbon (ZnS: Mn-NPs-AC) which fully was synthesized and characterized successfully applied for simultaneous removal of malachite green and methylene blue in binary situation. The effects of variables such as pH (2.0-10.0), sonication time (1-5min), adsorbent mass (0.005-0.025g) and MB and MG concentration (4-20mgL(-1)) on their removal efficiency was studied dy central composite design (CCD) to correlate dyes removal percentage to above mention variables that guides amongst the maximum influence was seen by changing the sonication time and adsorbent mass. Sonication time, adsorbent mass and pH in despite of dyes concentrations has positive relation with removal percentage. Multiple regression analysis of the experimental results is associated with 3-D response surface and contour plots that guide setting condition at pH of 7.0, 3min sonication time, 0.025g Mn: ZnS-NPs-AC and 15mgL(-1) of MB and MG lead to achievement of removal efficiencies of 99.87% and 98.56% for MG and MB, respectively. The pseudo-second-order model as best choice efficiency describe the dyes adsorption behavior, while MG and MB maximum adsorption capacity according to Langmuir was 202.43 and 191.57mgg(-1).

Central composite design and genetic algorithm applied for the optimization of ultrasonic-assisted removal of malachite green by ZnO Nanorod-loaded activated carbon

Maximum malachite green (MG) adsorption onto ZnO Nanorod-loaded activated carbon (ZnO-NR-AC) was achieved following the optimization of conditions, while the mass transfer was accelerated by ultrasonic. The central composite design (CCD) and genetic algorithm (GA) were used to estimate the effect of individual variables and their mutual interactions on the MG adsorption as response and to optimize the adsorption process. The ZnO-NR-AC surface morphology and its properties were identified via FESEM, XRD and FTIR. The adsorption equilibrium isotherm and kinetic models investigation revealed the well fit of the experimental data to Langmuir isotherm and pseudo-second-order kinetic model, respectively. It was shown that a small amount of ZnO-NR-AC (with adsorption capacity of 20mgg(-1)) is sufficient for the rapid removal of high amount of MG dye in short time (3.99min).

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.

Highly efficient simultaneous ultrasonic-assisted adsorption of Pb(II), Cd(II), Ni(II) and Cu (II) ions from aqueous solutions by graphene oxide modified with 2,2'-dipyridylamine: Central composite design optimization

In present work, a graphene oxide chemically modified with 2,2'-dipyridylamine (GO-DPA), was synthesized by simple, fast and low-cost process for the simultaneous adsorption of four toxic heavy metals, Pb(II), Cd(II), Ni(II) and Cu(II), from aqueous solutions. The synthesized adsorbent was characterized by FT-IR, XRD, XPS, SEM and AFM measurements. The effects of variables such as pH solution, initial ion concentrations, adsorbent dosage and sonicating time were investigated on adsorption efficiency by rotatable central composite design. The optimum conditions, specified as 8mg of adsorbent, 20mgL(-1) of each ion at pH 5 and short time of 4min led to the achievement of a high adsorption capacities. Ultrasonic power had important role in shortening the adsorption time of ions by enhancing the dispersion of adsorbent in solution. The adsorption kinetic studies and equilibrium isotherms for evaluating the mechanism of adsorption process showed a good fit to the pseudo-second order and Langmuir model, respectively. The maximum adsorption capacities (Qm) of this adsorbent were 369.749, 257.201, 180.893 and 358.824mgg(-1) for lead, cadmium, nickel and copper ions, respectively. The removal performance of adsorbent on the real wastewater samples also showed the feasibility of adsorbent for applying in industrial purposes.