Rapid removal of Auramine-O and Methylene blue by ZnS:Cu nanoparticles loaded on activated carbon: A response surface methodology approach

Remediation of organic pollutant from the aqueous environment using in-house fabricated polyaniline-based hybrid composite (PANI-MnPBA/NiCoMnS) materials

Polyaniline-based hybrid material (PANI-MnPBA/NiCoMnS) was prepared by hydrothermal-solvothermal approach. Synthesized hybrid material was characterized through FTIR-spectroscopy, p-XRD, SEM, EDX, BET, and Zetasizer techniques. Hybrid material as adsorbent for removal of Congo red (CR) from water system showed excellent results such as 98 % removal efficiency and 254 mg/g adsorption capacity. Furthermore, various studies like adsorption isothermal, kinetic, thermodynamic, and statistical analysis were performed to understand the adsorption phenomenon. From various kinetic models, pseudo-first and second-order kinetic models, intra-particle and liquid film diffusion kinetic models, pseudo-first-order kinetic model, and liquid-film diffusion kinetic model both are most suitable for explaining the adsorption phenomenon due to the greater value of R2 (0.955) for CR. According to these kinetic models, physio-sorption and diffusion play a basic role in the adsorption of CR. Moreover, ΔG (-1779.508 kJ mol-1) and ΔH (61,760.889 kJ mol-1) values explained the spontaneous and exothermic nature of the adsorption process, respectively. Furthermore, for support of the adsorption mechanism via electrostatic attractions before and after the adsorption process FTIR results of as-synthesized adsorbent were measured (NH peaks before 3668.88, after 3541.41 cm-1). These results confirm electrostatic attraction for the adsorption process. Finally, the statistical model was added (n < 1), according to this model, adsorption follows a multi-anchorage approach and adsorbent contains enough sites for adsorption of CR.

Efficient Degradation of Congo Red in Water by UV-Vis Driven CoMoO4/PDS Photo-Fenton System

In order to improve the catalytic activity of cobalt molybdate (CoMoO₄), a PDS-activated and UV-vis assisted system was constructed. CoMoO₄ was prepared by coprecipitation and calcination, and characterized by XRD, FTIR, Raman, SEM, TEM, XPS, TGA Zeta potential, BET, and UV-Vis DRS. The results showed that the morphology of the CoMoO₄ nanolumps consisted of stacked nanosheets. XRD indicated the monoclinic structures with C2/m (C³_2h, #12) space group, which belong to α-CoMoO₄, and both Co²⁺ and Mo⁶⁺ ions occupy distorted octahedral sites. The pH of the isoelectric point (pHIEP) of CMO-8 at pH = 4.88 and the band gap of CoMoO₄ was 1.92 eV. The catalytic activity of CoMoO₄ was evaluated by photo-Fenton degradation of Congo red (CR). The catalytic performance was affected by calcination temperature, catalyst dosage, PDS dosage, and pH. Under the best conditions (0.8 g/L CMO-8, PDS 1 mL), the degradation efficiency of CR was 96.972%. The excellent catalytic activity of CoMoO₄ was attributed to the synergistic effect of photo catalysis and CoMoO₄-activated PDS degradation. The capture experiments and the ESR showed that superoxide radical (·O₂^-), singlet oxygen (¹O₂), hole (h⁺), sulfate (SO₄^-·), and hydroxyl (·OH^-) were the main free radicals leading to the degradation of CR. The results can provide valuable information and support for the design and application of high-efficiency transition metal oxide catalysts.

New bismuth oxyiodide/chitosan nanocomposite for ultrasonic waves expedited adsorptive removal of amoxicillin from aqueous medium: kinetic, isotherm and thermodynamic investigations

Amoxicillin (AMX) is a widely used antibiotic, which induces harmful effects to nature via bioaccumulation and persistence in the environment if discharged untreated into water bodies. In the current study, a novel bionanocomposite, bismuth oxyiodide-chitosan (BiOI-Ch), was synthesized by a facile precipitation method and its amoxicillin (AMX) adsorption capacity in the presence of ultrasonic waves has been explored. Multiple batch experiments were performed to achieve the optimum operational parameters for maximum adsorption of AMX and the obtained results were as follows: pH 3, 80 mg g^-1 AMX concentration, 1.7 g L^-1 adsorbent dose, temperature 298 K and ultrasonication time 20 min. Composite removed approximately 90% AMX from the solution under optimized conditions, while the maximal adsorption capacity was determined to be 81.01 mg g^-1. BiOI-Ch exhibited superior adsorption capacity as compared to pure BiOI (33.78 mg g^-1). To understand the dynamics of reaction, several kinetic and isotherm models were also examined. The adsorption process obeyed pseudo-second-order kinetic model (R² = 0.98) and was well fitted to Freundlich isotherm (R² = 0.99). The addition of biowaste chitosan to non-toxic bismuth-based nanoparticles coupled with ultrasonication led to enhanced functional groups as well as surface area of the nanocomposite resulting in superior adsorption capacity, fast adsorption kinetics and improved mass transfer for the removal of AMX molecules. Thus, this study demonstrates the synergistic effect of ultrasonication in improved performance of novel BiOI-Ch for potential application in the elimination of persistent and detrimental pollutants from industrial effluent after necessary optimization for large-scale operation.

Synthesis and preparation of acid capped CdSe nanocrystals as successful adsorbent and photocatalyst for the removal of dyes from water and its statistical physics analysis

In this study, mercaptosuccinic acid capped CdSe nanocrystals were successfully synthesized and used as photocatalyst for the effective removal of methylene blue (MB) inaqueous solution under visible light and sunlight irradiations including its analysis with statistical physics theory. Dye adsorption properties of these nanocrystals were investigated via experimental kinetics and equilibrium studies. These experimental data were modeled via the application of statistical physics theory to explain the corresponding adsorption mechanism and to characterize the steric and energetic parameters involved in the dye removal. A maximum adsorption capacity of 27.07 mg g^-1 (80% of dye removal) was observed in 10 min using an initial concentration of 30 mg L^-1. Statistical physics calculations indicated that the adsorption energy was lower than 40 kJ mol^-1. It was also established that the dye adsorption was associated to the electrostatic interactions and hydrogen bonding where dye aggregation and multi-molecular adsorption were expected. Overall, the dye removal was a spontaneous, feasible and exothermic. It was concluded that adsorption properties of CdSe-MSA nanocrystals improved the dye photo-catalytic degradation efficiency under visible light thus achieving up to 80% degradation efficiency in 60 min. The synergic effect of adsorption and photo-catalytic degradation performance was mainly due to the surface area (136.43 m² g^-1), small size (3.7 nm), and structural defects (selenium vacancies S_e, interstitial of cadmium I_Cd) of CdSe nanocrystals, which enhanced both the response of these nanomaterials to visible light and their photo-catalytic activity. In summary, these nanocrystals are promising materials to be used in wastewater treatment under sunlight for the removal of organic compounds like dyes.

Activated Sawdust-Based Adsorbent for the Removal of Basic Blue 3 and Methylene Green from Aqueous Media

Dye pollution is a serious threat to aquatic environment and human health. Although activated carbon is an efficient adsorbent for dye reclamation from effluents, its expressive nature renders its use on large commercial scales. On the other hand, waste biomasses are not effectively used for any beneficial purposes. Sawdust is a waste biomass of wood mills, and due to its small particle sizes, it has the potential to be used as adsorbent. In spite of its uses for cooking purposes, it is sometimes used as adsorbent as such or converted into activated carbon. In raw form, it is not a good adsorbent; however, its adsorption capacity can be increased by applying chemical modifications. In the present study, sawdust of paper mulberry (Broussonetia papyrifera) was used as adsorbent for the removal of basic blue 3 and methylene green from water after chemical modification with NaOH and HCl in 1 : 1. The prepared adsorbent was characterized by SEM and FTIR, whereas the surface area was estimated through an already reported method in literature. Batch experiments were performed to determine the isothermal and kinetic parameters of the selected dyes adsorption on activated sawdust. The effect of adsorbent dosage and temperature on adsorption were also evaluated. The best fit of the kinetic data was achieved with pseudosecond-order model for which $R^2$ values were approximately equal to 1 whereas Langmuir model was most suitable model to explain the isothermal data. The optimum adsorbent dosage was 0.05 g for both of the selected dyes. Different thermodynamic parameters, such as enthalpy ( $∆H=18.5$ and 8.334 kJ/mol respectively for basic blue 3 and methylene green), entropy ( $∆S^{°}=62.41$ and 29.22 kJ/molK respectively for basic blue 3 and methylene green), and Gibbs free energy ( $∆G^{°}=-83.6$ , -410, and -1658 kJ/mol (basic blue)/-65, -519, and -1139 kJ/mol (methylene green), were estimated, and the process was found to be endothermic, spontaneous, and feasible. The increase in $\Delta G^{°}$ with increase in temperature indicates that the adsorption process is favorable at high temperature. The prepared adsorbent could be effectively used in the reclamation of water loaded with other contaminants; however, further experiments are needed to increase the adsorption capacity of the adsorbent.

Ultrasound-assisted adsorption on porous ceramic for removal of iron in water

This study proposes the use of an ultrasound-assisted adsorption system coupled to porous ceramic fragments to improve the removal of iron from FeSO₄ aqueous solution. Ultrasound was applied using an ultrasound bath at a low frequency (37 kHz, 330 W). The optimized conditions for Fe removal were achieved by 7 g of adsorbent, 40 min of sonication, 20 mg L^-1 of initial Fe concentration, and 30 °C of reaction temperature. After optimizing the conditions, the method was applied for the removal of iron in groundwater. A central composite design and response surface methodology were used to evaluate the degree to which different variables had a significant effect on iron removal. The efficiency of iron removal using the selected conditions for FeSO₄ solution was near to 100%. However, for groundwater samples, the maximum iron removal efficiencies of the system with and without ultrasound were 80.7% and 51.1%, respectively, indicating that the adsorption with ultrasound was significantly higher than that without ultrasound. It was shown that the proposed ultrasound-assisted adsorption system can be used to enhance the removal of inorganic iron from groundwater.

Activated biochar derived from spent Auricularia auricula substrate for the efficient adsorption of cationic azo dyes from single and binary adsorptive systems

In this study, spent Auricularia auricula substrate (AS)-derived biochar (ASBCs) and activated biochar with NaOH (A-ASBC) were evaluated for the adsorption of cationic azo dyes, including methylene blue (MB), rhodamine B (RB), and crystal violet (CV), from single and binary adsorptive systems. A-ASBC showed a higher maximum adsorption capacity for these dyes (MB: 53.62 mg·g^-1, RB: 32.33 mg·g^-1, CV: 735.73 mg·g^-1) than ASBCs in a single system because it had a greater specific surface area and more oxygen containing-functional groups on the surface. The adsorption process of the three dyes onto the adsorbents was in good agreement with the Freundlich adsorption isotherm and fit the pseudo-second-order kinetic model, which revealed sorbate polymolecular layer formation over the adsorbent surface and the involvement of chemisorption. The adsorption mechanism showed that the adsorption of three dyes on adsorbents could be postulated as a multistep process with extraordinary affinity-induced adsorption in terms of both physisorption and chemisorption. In the binary adsorptive system, the results showed that all MB, RB, and CV had antagonistic/competitive effects on each other's adsorption (Q_Binary/Q_Single < 1). Furthermore, a phytotoxic assay affirmed the effectiveness of the adsorbent in adsorbing dye species from aqueous solutions using Brassica pekinensis L. seeds as the model. Therefore, activated biochar prepared from AS can be used as a potentially economical and effective adsorbent for treating printing and dyeing wastewater.

Removal of hazardous dye from aqueous media using low-cost peanut (Arachis hypogaea) shells as adsorbents

In the present article, an attempt is made for simple, low-cost, and efficient removal of Auramine dye using peanut (Arachis hypogaea) shells as adsorbents. Two different forms of adsorbents distilled water washed peanut shells (DPS) and NaOH treated peanut shells (NPS) were used as adsorbents. Both the adsorbents were studied using BET, pH_PZC , FTIR, SEM, TGA, and XRD characterization techniques. Adsorption parameters such as effect of contact time, pH, initial dye concentration, adsorbent dose, and temperature were also assessed. Isotherm analysis at optimum conditions showed Langmuir fitted better with a q_m value of 96.15 mg/g for DPS and 294.12 mg/g for NPS; while in kinetic analysis, pseudo-second order was superior. Thermodynamics study stated that adsorption process was endothermic in nature. Overall outcomes establish that the two forms of peanut shells, DPS, and NPS were excellent in removal of Auramine dye and are low cost also as preparation cost of DPS and NPS is 68.73 INR and 106.19 INR per kg, respectively. PRACTITIONER POINTS: Removal of Auramine dye from aqueous media using different forms of peanut (Arachis hypogaea) shells as adsorbents is discussed. q_m (Langmuir) using DPS and NPS were found to be 96.15 and 294.12 mg/g, respectively. Preparation cost of DPS was 68.73 INR per 1 kg, whereas for NPS it was 106.19 INR per 1 kg.

Optimizing Adsorption of 17α-Ethinylestradiol from Water by Magnetic MXene Using Response Surface Methodology and Adsorption Kinetics, Isotherm, and Thermodynamics Studies

Magnetic MXene composite Fe3O4@Ti3C2 was successfully prepared and employed as 17α-ethinylestradiol (EE2) adsorbent from water solution. The response surface methodology was employed to investigate the interactive effects of adsorption parameters (adsorption time, pH of the solution, initial concentration, and the adsorbent dose) and optimize these parameters for obtaining maximum adsorption efficiency of EE2. The significance of independent variables and their interactions were tested by the analysis of variance (ANOVA) and t-test statistics. Optimization of the process variables for maximum adsorption of EE2 by Fe3O4@Ti3C2 was performed using the quadratic model. The model predicted maximum adsorption of 97.08% under the optimum conditions of the independent variables (adsorption time 6.7 h, pH of the solution 6.4, initial EE2 concentration 0.98 mg L-1, and the adsorbent dose 88.9 mg L-1) was very close to the experimental value (95.34%). pH showed the highest level of significance with the percent contribution (63.86%) as compared to other factors. The interactive influences of pH and initial concentration on EE2 adsorption efficiency were significant (p < 0.05). The goodness of fit of the model was checked by the coefficient of determination (R2) between the experimental and predicted values of the response variable. The response surface methodology successfully reflects the impact of various factors and optimized the process variables for EE2 adsorption. The kinetic adsorption data for EE2 fitted well with a pseudo-second-order model, while the equilibrium data followed Langmuir isotherms. Thermodynamic analysis indicated that the adsorption was a spontaneous and endothermic process. Therefore, Fe3O4@Ti3C2 composite present the outstanding capacity to be employed in the remediation of EE2 contaminated wastewaters.

Preparation of Pd–Ni Nanoparticles Supported on Activated Carbon for Efficient Removal of Basic Blue 3 from Water

Pd–Ni nanoparticles supported on activated carbon (Pd–Ni/AC) were prepared using a phase transfer method. The purpose of synthesizing ternary composites was to enhance the surface area of synthesized Pd–Ni nanoparticles, as they have a low surface area. The resulting composite was characterized by scanning electronic microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) for investigating its surface morphology, particle size, percentage of crystallinity and elemental composition, respectively. The XRD data and EDX analysis revealed the presence of Pd–Ni alloys impregnated on the AC. Pd–Ni/AC was used as an adsorbent for the removal of the azo dye basic blue 3 from an aqueous medium. Kinetic and isotherm models were used to calculate the adsorption parameters. The most suitable kinetic model amongst the applied models was the pseudo-second-order model, confirming the chemisorption characteristics of the process, and the most suitable isotherm model was the Langmuir model, with a maximum adsorption capacity of 333 mg/g at 333 K. Different experimental parameters, such as the adsorbent dosage, pH, temperature and contact time, were optimized. The optimum parameters reached were: a pH of 12, temperature of 333 K, adsorbent dosage of 0.01 g and optimum contact time of 30 min. Moreover, the thermodynamics parameters of adsorption, such as Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°), showed the adsorption processes being exothermic with values of ΔH° equal to −6.206 kJ/mol and being spontaneous with ΔG° values of −13.297, −13.780 and −14.264 kJ/mol, respectively at 293, 313 and 333 K. An increase in entropy change (ΔS°) with a value of 0.0242 kJ/mol K, indicated the enhanced disorder at a solid–solution interface during the adsorption process. Recycling the adsorbent for six cycles with sodium hydroxide and ethanol showed a decline in the efficiency of the selected azo dye basic blue 3 up to 79%. The prepared ternary composite was found effective in the removal of the selected dye. The removal of other pollutants represents one of the possible future uses of the prepared adsorbent, but further experiments are required.

Synthesis and Characterization of Pd-Ni Bimetallic Nanoparticles as Efficient Adsorbent for the Removal of Acid Orange 8 Present in Wastewater

In this study palladium-nickel (Pd-Ni) nanoparticles supported on carbon and cerium oxide (Pd-Ni/AC-CeO2) were synthesized by a transfer phase method and characterized by scanning electronic microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX). The XRD and SEM data concluded the presence of alloy formation between Pd and Ni. The synthesized particles were used as an adsorbent for removal of azo dye acid orange-8 (AO-8) from water and were found to be effective in removal (over 90% removal efficiency) of the selected dye. Different kinetics and equilibrium models were applied to calculate the adsorption parameters. The most suitable model that best fitted the equilibrium data was the Langmuir model and maximum adsorption capacities were 666.6, 714 and 769 mg/g at 293, 313 and 333 K, respectively, with R2 values closed to 1 while in the case of the kinetics data the best fit was obtained with a pseudo-second order kinetics model with a high R2 value. Furthermore, the adsorption thermodynamics parameters such as free energy, enthalpy, and entropy were calculated and the adsorption process was to found be exothermic with a value of ΔH° (−7.593 kJ mol−1), spontaneous as ΔG° values were negative (−18.7327, −19.4870, and −20.584 kJ/mol at 293, 313 and 333 K, respectively). A positive entropy change ΔS° with a value of 0.0384 kJ /mol K indicates increased disorder at the solid–solution interface during the adsorption process. An attempt was made to recycle the Pd-Ni/AC-CeO2 with suitable solvents and the recycled adsorbent was reused for 6 cycles with AO-8 removal efficiency up to 80%. Based on findings of the study, the synthesized adsorbent could effectively be used for the removal of other pollutants from wastewater, however, further studies are needed to prove the mechanisms.

Chiral poly(amide-imide)/ZnS nanocomposite as a new adsorbent for simultaneous removal of cationic dyes from aqueous solution

A new adsorbent, poly(amide-imide)/zinc sulfide nanocomposite (PAI/ZnS NC), was fabricated and identified by Fourier-transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, field emission-scanning electron microscopy, and transmission electron microscopy. Then, the obtained NC was applied for the simultaneous removal of auramine O (AO) and rhodamine B (RB) dyes from aqueous solution via the interactions of hydrogen bonding, π– π stacking, and Lewis acid–base interaction. The effects of operational variables including pH, PAI/ZnS NC mass, AO and RB concentration, and sonication time on removal efficiency were examined and optimized values were found to be 8.0, 16 mg, 11 mg L−1, and 6 min, respectively. The adsorption capacities of PAI/ZnS NC for the removal of AO and RB dyes were found to be 70.92 and 91.74 mg g−1, respectively. Ultraviolet–visible spectrophotometer was used to determine the amount of residual dye in solution. Fitting the experimental equilibrium data to isotherm models such as Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich reveals the suitability of the Langmuir model with high correlation coefficients ( R2 = 0.998 for AO and R2 = 0.999 for RB). Pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich kinetic models applicability was tested and the pseudo-second-order equation controls the kinetics of the adsorption process. Furthermore, this study establishes that PAI/ZnS NC can be successfully applied as a low-cost adsorbent and conserve its high efficiency after nine cycles for the removal of AO and RB dyes.

Adsorption characteristics of chloramphenicol onto powdered activated carbon and its desorption performance by ultrasound

In this work, the adsorption characteristics, including adsorption kinetic, isotherm and thermodynamics of chloramphenicol (CAP) onto powdered activated carbon (PAC), were carried out, and the feasibility of using ultrasound to regenerate saturated PAC in aqueous solution was evaluated. The adsorption results demonstrated that the adsorption mechanism was a complex process including surface adsorption, external liquid membrane diffusion and intraparticle diffusion as well, and the adsorption process was endothermic and non-spontaneous. The optimal conditions for PAC regeneration were as follows: acoustic density of 0.36 W/mL, saturated carbon dosage of 1.0 g/L and pH value of 10.36. The analysis of thermogravimetric analysis (TGA), Fourier transform infrared spectrometry (FTIR), Brunauer-Emmett-Teller (BET) surface area, pore size distribution and scanning electron microscopy (SEM) of PAC samples revealed that ultrasound mainly acted on surface functionalities, meso-pores and macro-pores of PAC through hydroxyl radical oxidization, high-pressure shock waves and high-speed microjets due to cavitation effect. This study highlighted that ultrasound could be efficiently desorbing CAP from saturated PAC. Practical applications of this method for PAC regeneration with complex natural matrices under environmentally realistic conditions were conducted and the adsorption capacity of the regenerated PAC decreased.

Treatment of malachite green dye containing solution using bio-degradable Sodium alginate/NaOH treated activated sugarcane baggsse charcoal beads: Batch, optimization using response surface methodology and continuous fixed bed column study

In this study, carbonized material was produced using sodium hydroxide treated Sugar cane bagasse (SB), and synthesized materials ware used to prepare Sodium Alginate/SBAC composite beads which were further used as an adsorbent to remove malachite green dye (MG) present in water. Physiochemical characteristics of composite beads were analyzed using FTIR, SEM, TGA, and BET. Adsorption equilibrium data showed excellent fit to the Freundlich model (R² = 0.994) than to the Langmuir model (R² = 0.925). Adsorption kinetics study indicated that the MG removal process would be better described by the pseudo-second-order kinetic model. The thermodynamic study suggested the spontaneous and endothermic nature of MG adsorption. By using response surface methodology, the optimum conditions for MG adsorption on composite beads were found to be 115.43 min, 0.3 g/L and pH 8 for contact time, adsorbent mass, and pH respectively and MG adsorption efficiency was 97.88%. The fixed-bed column data were evaluated using several kinetic models and among them, Thomas model showed the best agreement with investigation results. These results revealed that synthesized composite beads have a high affinity toward MG and it could be reasonable, eco-friendly adsorbent for dye removal from wastewater.

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.

New MOF/COF Hybrid as a Robust Adsorbent for Simultaneous Removal of Auramine O and Rhodamine B Dyes

In this study, by hybridization of zinc-based metal-organic framework-5 (MOF-5) and melamine-terephthaldehyde-based intergrade two-dimensional π-conjugated covalent organic framework (COF), a novel MOF-5/COF (M5C) hybrid material was prepared and characterized by Fourier transform infrared, field emission scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis. MOF-5 has a well-defined cubic structure, and the proposed COF has an orderly and spherical nanosize shape. The prepared MOF-5/COF was applied as an effective adsorbent for rapid and high-efficient simultaneous removal of auramine O (AO) and rhodamine B (RB) cationic dyes via electrostatic, H-bonding, Lewis acid-base interactions, and π-π stacking from aqueous solution. The effect of experimental parameters such as pH, M5C mass, contact time, and AO and RB dyes concentration was investigated for removal efficiency and optimized. The M5C adsorbent showed an adsorption capacity of 17.95 and 16.18 mg/g for AO and RB dyes, respectively, at pH 9.5. The adsorption study of AO and RB dyes by M5C comprises both isotherm and kinetic studies. The equilibrium adsorption data followed by Langmuir isotherm and the adsorption kinetic process were found to be a pseudo-second-order model. The robustness adsorption efficiency of MOF/COF hybrids can be attributed to the formation of amide bonds between COF and MOFs, which improve the stability of the adsorbent.

Heterogeneous degradation of organic contaminant by peroxydisulfate catalyzed by activated carbon cloth

An eco-friendly material, activated carbon cloth (ACC) was used as the heterogeneous catalyst in activation of peroxydisulfate (PDS) for the efficient degradation of organic pollutant in water. Besides, the effects of several parameters in the ACC/PDS process including initial pH, PDS concentration, reaction temperature, stirring speed and co-existing anions were investigated. Under optimum conditions, almost complete removal (98.6%) of AO7 in 60 min and 67.4% of total organic carbon (TOC) removal within 180 min were obtained, accompanied by the remarkable destruction of azo band and naphthalene ring on AO7. The electron paramagnetic resonance and radical quenching experiments were carried out to identify the reactive radicals in the ACC/PDS process. Surface characteristic techniques such as XRD, BET, SEM, FTIR, XPS were applied to analysis the change of crystal structure, surface area, surface morphology, functional groups on the surface of fresh and spent ACC samples. Hydroxyl groups (C‒OH) and π-π transitions significantly affected the catalytic activity of ACC. The intermediate products of AO7 oxidation were identified by LC-MS and the corresponding degradation pathway was proposed.

Adsorptive Removal of Recalcitrant Auramine-O Dye by Sodium Dodecyl Sulfate Functionalized Magnetite Nanoparticles: Isotherm, Kinetics, and Fixed-Bed Column Studies

Presently, the treatment of dye-polluted water is a challenging task worldwide. In this study, the adsorptive removal of Auramine-O (AO) dye by magnetite nanoparticles (MNs) and sodium dodecyl sulfate (SDS) functionalized MNs (SFMNs) were investigated. FESEM, HRTEM, EDX, and XRD were employed to characterize the MNs. In batch optimization, dye removal efficiency of 74% was obtained at contact time (40[Formula: see text]min), pH 6.5, sorbent dosage (20[Formula: see text]mg), and initial dye concentration (20[Formula: see text]mg/L). The maximum adsorption capacity of 55.56[Formula: see text]mg/g was estimated from Langmuir model and the isotherm data were fitted with Freundlich model ([Formula: see text]) for SFMNs. Pseudo-second-order kinetics was followed by both MNs and SFMNs for the adsorption of AO dye. The continuous AO dye adsorption was studied in fixed-bed column and the effects of bed height, influent flow rate, and initial dye concentration were investigated. The column performance was evaluated by breakthrough kinetic modeling and Yoon–Nelson model was fitted with the data. The results of this study showed that the surface modification of MNs using SDS enhanced the AO dye removal efficiency and SFMNs can be employed as an efficient nanoadsorbent for AO dye removal in batch and continuous mode of operation.

A study by response surface methodology (RSM) on optimization of phosphorus adsorption with nano spherical calcium carbonate derived from waste

A nano spherical CaCO₃ (NSC) derived from solid waste (precipitated from tris(α-chloropropyl) phosphate and triethyl phosphate mixed wastewater) was prepared as adsorbent for phosphorus removal from aqueous solution. Response surface methodology (RSM) was used to develop an approach for the evaluation of phosphorus adsorption process, and Box-Behnken design was performed to investigate the effects of various experimental parameters (temperature, contact time, initial pH and dosage of absorbent) on phosphorus adsorption. The model results of experimental data gave a high correlation coefficient (R² = 0.9658), and a predictive model of quadratic polynomial regression equation and optimum level values were established successfully. It was found that the adsorption efficiency and adsorption capacity reached 97.05% and 123.79 mg/g, respectively, under conditions of temperature of 45 °C, initial pH 5.3, contact time of 11 h, and absorbent amount of 392 mg/L. X-ray diffraction (XRD) analysis testified new phase, Ca₁₀(PO4)₆CO₃, was produced in the adsorption process. Apart from that, adsorption behavior fitted well with the Langmuir isotherm model and logistic growth model. The thermodynamic study indicated that phosphorus removal by NSC as adsorbent was a spontaneous, endothermic, and mainly chemical adsorption process.

Preparation and in vitro release kinetics of ivermectin sustained-release bolus optimized by response surface methodology

Sustained-release formulations of ivermectin (IVM) are useful for controlling parasitic diseases in animals. In this work, an IVM bolus made from microcrystalline cellulose (MCC), starch and low-substituted hydroxypropyl cellulose (LS-HPC) was optimized by response surface methodology. The bolus was dissolved in a cup containing 900 mL of dissolution medium at 39.5 °C, under with stirring at 100 rpm. A quadratic model was formulated using analysis of variance according to the dissolution time. The optimized formulation of the bolus contained 8% MCC, 0.5% starch, and 0.25% LS-HPC. The length, width, and height of the prepared IVM bolus were 28.12 ± 0.14, 16.1 ± 0.13, and 13.03 ± 0.05 mm, respectively. The bolus weighed 11.4842 ± 0.1675 g (with a density of 1.95 g/cm³) and contained 458.26 ± 6.68 mg of IVM. It exhibited in vitro sustained-release for over 60 days, with a cumulative amount and percentage of released IVM of 423.72 ± 5.48 mg and 92.52 ± 1.20%, respectively. The Korsmeyer–Peppas model provided the best fit to the dissolution release kinetics, exhibiting an R² value close to 1 and the lowest Akaike Information Criterion among different models. The parameter n (0.5180) of the Korsmeyer–Peppas model was between 0.45 and 0.89. It was demonstrated that the release mechanism of the IVM bolus followed a diffusive erosion style.

A comparative study between fungal pellet- and spore-assisted microalgae harvesting methods for algae bioflocculation

Fungi assisted microalgae bioflocculation is an emerging, efficient and cost-effective microalgal harvesting method, but no study has systematically evaluated and compared fungal spore-assisted (FSA) and fungal pellet-assisted (FPA) microalgal harvesting methods. In this study, harvesting Chlorella sp. cells by co-culture with Penicillium sp. spores or pellets was compared. Temperature, glucose concentration, pH and fungi:algae ratio were the critical parameters for harvesting efficiency. The highest flocculation efficiency (99%) of FSA method was achieved in 28 h at 40 °C, 160 rpm, 5 g glucose/L and 1.1 × 10⁴ cells/mL (spore). FPA method can harvest 98.26% algae cells in 2.5 h at 34 °C, 160 rpm, pH 4.0 with the fungi:algae ratio of 1:2. The carbon input for FPA is only half of that for FSA. FPA takes less time and needs less glucose input compared with FSA and may be more promising to be further developed as an effective microalgae bioflocculation method.

Gum xanthan-psyllium-cl-poly(acrylic acid-co-itaconic acid) based adsorbent for effective removal of cationic and anionic dyes: Adsorption isotherms, kinetics and thermodynamic studies

The present work highlights the synthesis of the adsorbent based on Gum xanthan-psyllium hybrid backbone graft co-polymerized with polyacrylic acid-co-polyitaconic acid chains for the rapid sequestration of auramine-O (Aur-O) and eriochrome black-T (EBT) dyes from the aqueous fluid. The excellent dye removal efficiency of 90.53% for EBT and 95.63% for Aur-O was found at initial dye concentration of 30mgL^-1 (EBT) and 15 mgL^-1 (Aur-O) 40mL^-1 with an adsorbent dose of 600mg within time duration of 5h and 323K temp. The adsorption isotherm data fitted well with Langmuir isotherm and Freundlich isotherm for Aur-O and EBT dyes (R² ≥ 0.90), respectively. The adsorption kinetics depicted that pseudo-second order kinetics was followed simultaneously with intra-particle diffusion for both the dyes. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were also calculated and confirmed the spontaneity, randomness and endothermic nature of the adsorption process. Further, the adsorbent exhibited good recyclability efficiency for the capture of Aur-O and EBT from aqueous solution with minimal activity decline after six and three cycles, respectively. So, the synthesized adsorbent could be used successfully by the textile industries for the treatment of dye contaminated water with excellent competency.

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.

Combined Homogeneous Surface Diffusion Model - Design of experiments approach to optimize dye adsorption considering both equilibrium and kinetic aspects

Adsorption, a popular technique for removing azo dyes from aqueous streams, is influenced by several factors such as pH, initial dye concentration, temperature and adsorbent dosage. Any strategy that seeks to identify optimal conditions involving these factors, should take into account both kinetic and equilibrium aspects since they influence rate and extent of removal by adsorption. Hence rigorous kinetics and accurate equilibrium models are required. In this work, the experimental investigations pertaining to adsorption of acid orange 10 dye (AO10) on activated carbon were carried out using Central Composite Design (CCD) strategy. The significant factors that affected adsorption were identified to be solution temperature, solution pH, adsorbent dosage and initial solution concentration. Thermodynamic analysis showed the endothermic nature of the dye adsorption process. The kinetics of adsorption has been rigorously modeled using the Homogeneous Surface Diffusion Model (HSDM) after incorporating the non-linear Freundlich adsorption isotherm. Optimization was performed for kinetic parameters (color removal time and surface diffusion coefficient) as well as the equilibrium affected response viz. percentage removal. Finally, the optimum conditions predicted were experimentally validated.

Synthesis of ZnO-nanorod-based materials for antibacterial, antifungal activities, DNA cleavage and efficient ultrasound-assisted dyes adsorption

Undoped and Au-doped ZnO-nanorods were synthesized in the presence of ultrasound and loaded on activated carbon following characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmittance electron microscopy (TEM), UV-vis spectrophotometry and Fourier transform infrared spectroscopy (FTIR). The Au-doped ZnO-nanorod-loaded activated carbon (Au-ZnO-NRs-AC) was used for the simultaneous removal of methylene blue (MB) and auramine O (AO) from aqueous solutions. Central composite design (CCD) under response surface methodology (RSM) was applied to model and optimize the dyes removal versus adsorbent mass, pH, and initial dyes concentration and sonication time as well as to investigate the possible interaction between these variables. The optimum values of the initial MB and AO dyes concentration, adsorbent mass, pH and sonication time were found to be 12 and 10mgL^-1, 0.0124g, 6.4, and 4min respectively. The rapid adsorption process at neutral pH using very small amount of the adsorbent makes it promising for the wastewater treatment applications. More than 99.5% of both dyes was removed with maximum adsorption capacities in binary-component system (107.5 and 95.7mgg^-1 for MB and AO, respectively). The kinetics and isotherm studies showed that the second-order and Langmuir models apply for the kinetics and isotherm of the adsorption of MB and AO on the adsorbent used here. Moreover, the wastewater treatment by using an antibacterial/antifungal adsorbent makes the process much more valuable. Therefore, additional studies were performed which showed efficient antibacterial/antifungal activities and DNA cleavage of undoped and Au-doped ZnO nanorods as constituent of the adsorbent applied here.

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.

Synthesis of carbon loaded γ-Fe2O3 nanocomposite and their applicability for the selective removal of binary mixture of dyes by ultrasonic adsorption based on response surface methodology

The contemporary problems concerning water purification could be resolved by using nanosorbents. The present studies emphasis on the synthesis of γ-Fe₂O₃-activated carbon nanocomposites (γ-Fe₂O₃-NP-AC) by sol-gel method. The composition and surface morphology of them were studied by FTIR, EDS, SEM and XRD techniques. Moreover they were employed for the selective removal of binary mixture of dyes including reactive red 223 dye (RR) and Malachite Green dye (MG) by ultrasonic assisted adsorption method. Sonication is the act of applying sound energy to agitate particles in the sample. The ultrasonic frequencies (>20kHz) were used to agitate experimental solutions in current studies. The response surface methodology based on 5 factorial central composite design (CCD) was employed to investigate the optimum parameters of adsorption. The optimum operating parameters (OOP) including sonication time, solution pH, amount of adsorbent, concentration of RR and MG were estimated for the selective removal of mixture of dyes. On OOP conditions of RR, the % removal of RR and MG were observed to be 92.12% and 10.05% respectively. While at OOP of MG, the % removal of MG and RR were observed to be 85.32% and 32.13% from the mixture respectively. Moreover the mechanisms of adsorption of RR and MG on the γ-Fe₂O₃-NP-AC were also illustrated. The significance of the RR-γ-Fe₂O₃-NP-AC and MG-γ-Fe₂O₃-NP-AC adsorption models was affirmed by ANOVA test. The Pareto plots for the selective removal of the RR and MG from the binary mixture also confirm the significance of the factors. Isothermal studies were performed and RR adsorption was observed to follow Langmuir isotherm model whereas MG adsorption was observed to follow Freundlich model. Thermodynamic studies were conducted and the outcomes suggested the spontaneous nature of adsorption processes. The kinetic models were employed to study the kinetics of the process. It was observed that the system followed pseudo second order, intra-particle diffusion and Elovich models as represented by the R² values of the respective models. The comparative study from the previously studies revealed that the proposed method is amongst them is the most efficient method to eliminate RR and MG dyes from the aqueous medium. Therefore the current study will be useful in reducing the toxicity of RR and MG contaminated effluent.

Application of experimental design and derivative spectrophotometry methods in optimization and analysis of biosorption of binary mixtures of basic dyes from aqueous solutions

Simultaneous biosorption of malachite green (MG) and crystal violet (CV) on biosorbent Yarrowia lipolytica ISF7 was studied. An appropriate derivative spectrophotometry technique was used to evaluate the concentration of each dye in binary solutions, despite significant interferences in visible light absorbances. The effects of pH, temperature, growth time, initial MG and CV concentration in batch experiments were assessed using Design of Experiment (DOE) according to central composite second order response surface methodology (RSM). The analysis showed that the greatest biosorption efficiency (>99% for both dyes) can be obtained at pH 7.0, T=28°C, 24h mixing and 20mgL^-1 initial concentrations for both MG and CV dyes. The quadratic constructed equation ability for fitting experimental data is judged based on criterions like R² values, significant p and lack-of-fit value strongly confirm its high adequacy and applicability for prediction of revel behavior of the system under study. The proposed model showed very high correlation coefficients (R²=0.9997 for CV and R²=0.9989 for MG), while supported by closeness of predicted and experimental value. A kinetic analysis was carried out, showing that for both dyes a pseudo-second order kinetic model adequately describes the available data. The Langmuir isotherm model in single and binary components has better performance for description of dyes biosorption with maximum monolayer biosorption capacity of 59.4 and 62.7mgg^-1 in single component and 46.4 and 50.0mgg^-1 for CV and MB in binary components, respectively. The surface structure of biosorbents and the possible biosorbents-dyes interactions between were also evaluated by Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The values of thermodynamic parameters including ΔG° and ΔH° strongly confirm which method is spontaneous and endothermic.

Sequestration of dyes from artificially prepared textile effluent using RSM-CCD optimized hybrid backbone based adsorbent-kinetic and equilibrium studies

Present work reports the synthesis of semi-Interpenetrating Network Polymer (semi-IPN) using Gelatin-Gum xanthan hybrid backbone and polyvinyl alcohol in presence of l-tartaric acid and ammonium persulphate as the crosslinker-initiator system. Reaction parameters were optimized with Response Surface Methodology (RSM) in order to maximize the percent gel fraction of the synthesized sample. Polyvinyl alcohol, l-Tartaric acid, ammonium persulphate, reaction temperature, time and pH of the reaction medium were found to make an impact on the percentage gel fraction obtained. Incorporation of polyvinyl alcohol chains onto hybrid backbone and crosslinking between the different polymer chains were confirmed through techniques like FTIR, SEM-EDX and XRD. Semi-IPN was found to be very efficient in the removal of cationic dyes rhodamine-B (70%) and auramine-O (63%) from a mixture with an adsorbent dose of 700 mg, initial concentration of rhodamine-B 6 mgL^-1 and auramine-O 26 mgL^-1, at an time interval of 22-25 h and 30 °C temp. Further to determine the nature of adsorption Langmuir and Freundlich adsorption isotherm models were studied and it was found that Langmuir adsorption isotherm was the best fit model for the removal of mixture of dyes. Kinetic studies for the sorption of dyes favored the reaction mechanism to occur via a pseudo second order pathway with R² value about 0.99.