Adsorption Of Cationic Dyes Research Articles

Effect of Washing Temperature on Adsorption of Cationic Dyes by Raw Lignocellulosic Biomass

This study evaluated the potential of using raw Maclura pomifera and wild carob for the treatment of methylene blue (MB) and crystal violet (CV) as part of the search for new, abundant, and cost-effective natural materials applicable for wastewater treatment. Additionally, it explored the impact of washing water temperature on the adsorption performance of these raw organic materials. The physicochemical properties of the materials were characterized using BET, SEM/EDS, and FTIR analyses. The effects of various experimental parameters were investigated through batch adsorption experiments. The results demonstrated that the influence of washing water temperature was material-dependent. For Maclura pomifera, the maximum adsorption capacity of methylene blue and crystal violet decreased from 134.4 and 136.6 mg g−1 for MPC to 67.1 and 90.5 mg g−1 for MPH. In contrast, the adsorption capacities of wild carob biosorbents remained consistent, with the maximum amounts adsorbed for methylene blue and crystal violet by CC, CW, and CH being close, around 78.8 and 98.9 mg g−1, respectively, indicating a minimal effect of washing temperature on this material. The adsorption of both dyes onto the adsorbents was positively affected by increasing the pH, contact time, and initial dye concentration and was negatively affected by increasing adsorbent dose or ionic strength. Adsorption isotherms and kinetics were modeled using various mathematical approaches. The kinetic data were accurately described by a pseudo-second-order model, with a significant contribution from intraparticle diffusion. The Sips and Redlich–Peterson models provided the best fit for the adsorption isotherms of both dyes on the biosorbents. These findings confirm that the selected biomaterials are excellent adsorbents for the removal of cationic dyes.

Preparation and characterisation of chitosan/bacterial Escherichia coli biocomposite for malachite green dye removal: modeling and optimisation of the adsorption process

ABSTRACT Herein, a new biocomposite was obtained by loading a bacterial suspension of Escherichia coli onto a chitosan matrix to produce a unique biocomposite (chitosan – E. coli) with effective properties for biosorption of malachite green dye from water. The physicochemical characteristics of the chitosan – E. coli biocomposite were studied by employing XRD, FTIR, FESEM-EDX and pHpzc. The optimisation of biosorption conditions was achieved using a Box-Behnken Design (RSM-BBD) to assess the effect of variables on the dye removal: biocomposite dose (0.02–0.1 g/100 mL), pH (4–8) and contact time (10–300 min). The optimal conditions for dye removal (84.3%) were achieved with a chitosan – E. coli dose of 0.1 g/100 mL, and a contact time of 160 minutes with a pH of 8. The equilibrium and kinetic experimental findings show the biosorption of malachite green dye by chitosan – E. coli follows the Langmuir and pseudo-second-order models, respectively. The maximum dye adsorption capacity (q max ) of malachite green for the chitosan – E. coli biocomposite was 164.7 mg/g, where the dye adsorption mechanism was attributed to several effects such as hydrogen bonding, n-π interactions, and electrostatic attraction. Thermodynamic analysis indicated that the biosorption process was spontaneous and endothermic, with a positive enthalpy change (ΔH° = 40.9 kJ/mol) and a negative Gibbs free energy (ΔG°) at all tested temperatures. The biocomposite chitosan – E. coli adsorbent exhibits favourable cationic dye adsorption that is anticipated to have utility for remediation of dye effluent in industrial wastewater.

Identification of the degree of aging and adsorption behaviors of the naturally aged microplastics

Microplastics (MPs) inevitably experienced various aging processes in nature may exhibit varied and complex interfacial interactions with adjacent species. Therefore, clarifying the possible interfacial interactions between naturally aged MPs and organic pollutants is of great significance to assess the actual behaviors of MPs in the environment. Here several plastic packaging materials after use were employed as the raw materials and representatives of naturally aged MPs, the alteration of surface characteristics, especially the degree of aging and the adsorption properties of MPs for anionic and cationic dyes were investigated. The types and the degree of aging of MPs were identified, and the variation of oxygen-containing functional groups (carbonyl, hydroxyl, and ester groups), the hydrophilicity and surface charge character were characterized. The fitting results of kinetics and isotherm models indicated that the adsorption was mainly multi-layer on heterogeneous surfaces, with hydrogen bonding, electrostatic attraction, polar interaction, and hydrophobic partitioning possibly involving. The hydrogen bond interaction was further confirmed by FTIR spectra. The increased temperature promoted the adsorption of cationic dyes on MPs, and the increased salinity of the solution enhanced the uptake of most of the tested dyes by MPs. This research deepened the understanding on the aging degree of MPs and their interfacial interactions with hydrophilic pollutants, and provided vital information for MPs as pollutant carriers.

Preparation and characterization of oat hulls-filled-sodium alginate biocomposite microbeads for the effective adsorption of toxic methylene blue dye

In this work, the performance of oat hull-filled sodium alginate (SA-O) biocomposite microbeads in the adsorptive removal of methylene blue (MB) dye was examined. First, oat hulls were pulverized and biocomposite gels containing different weight ratios of oat hulls (10 %, 20 %, and 30 %, concerning the SA amount) were prepared by dispersing them in SA solution by ultrasonic homogenization method. Finally, gels were cross-linked by dropping into a 2 % CaCl2 solution. The study revealed that the optimal adsorbent dosage was 0.025 g/50 mL, pH was roughly 6–8, and the contact time was 120 min. According to isotherm models, the non-linear Sips and Langmuir model was more appropriate compare to other isotherms from error analysis, with a maximum adsorption capacity of 687.65 mg/g and 757.57 mg/g at 298 K, respectively. Furthermore, the non-linear kinetic data and error analyzes demonstrated that the process followed the pseudo-second-order kinetic. The adsorption process was exothermic (∆H°=−17.71 kJ/mol) and spontaneous (∆G°=−26.23 kJ/mol) at 298 K, based on thermodynamic characteristics. Furthermore, reusability investigations demonstrated that the adsorbent retained its performance with no major changes in characteristics. This work reveals that highly efficient, low-cost, sustainable, and eco-friendly SA-O composites with properties might be useful adsorbents for cationic dye adsorption.

Electrospinning of Sodium Alginate/Copper Oxide Nanofibrous Composite Membrane and Its Application of Cationic Dye Adsorption

AbstractDye wastewater is becoming one of the most significant sources of water pollution, and its impact on human survival is immeasurable. In this study, we successfully synthesized a nanofiber membrane with environmentally friendly and efficient properties using electrospinning of a mixture of sodium alginate (SA) and copper oxide (CuO) nanoparticles, aimed at effective dye removal. The adsorption performance of the SA/CuO nanofiber membrane was evaluated using the cationic dye methylene blue (MB). The maximum adsorption capacity of the nanofiber membrane was increased significantly with the addition of CuO nanoparticles, reaching a maximum value of 1633.4 mg g−1, almost twice as much as that of pure SA membrane. The adsorption kinetics follows the pseudo‐second‐order model, where chemisorption acts as the rate‐limiting step. The adsorption isotherm data indicate that the adsorption is monolayer. The nanofibrous membranes showed better dye removal under an alkaline environment. After four cycles of adsorption/desorption, the MB removal efficiency remained at 70.1% of the original adsorption capacity. The addition of CuO nanoparticles facilitated the adsorption of MB dyes, while the form of the nanofibrous membrane is easily recoverable and reusable. Therefore, the as‐prepared SA/CuO nanofibrous composite membrane is a potentially favorable adsorbent material for wastewater treatment applications.

Biobased amphoteric aerogel with core-shell structure for the hierarchically efficient adsorption of anionic and cationic dyes

Efficient and simultaneous removal of anionic and cationic dyes from wastewater using low-cost and environmentally-friendly adsorbent is highly required. Herein, the carboxylated cellulose (carboxyl content: 2.97 mmol/g) derived from pomelo peel was extracted by a one-step H2O2/H2SO4-mediated oxidation method. Subsequently, a novel pomelo-peel cellulose/chitosan/sodium alginate (PCS) amphoteric aerogel with a specific core-shell structure was synthesized by multiple physical cross-linking strategies. The shell layer and core layer of the optimized P3CS0.75 aerogel can selectively adsorb cationic dyes and anionic dyes, in which, the theoretical maximum adsorption capacities were 888.27 mg/g and 1816.87 mg/g towards methylene blue (MB) and Congo red (CR), respectively. Especially, the aerogel’s core/shell layer exhibited hierarchical adsorption behavior without overlapping sites even in the binary dye systems. The adsorption performance of obtained amphoteric aerogel remained effective in a wide pH range and under different practical water systems. Moreover, the removal efficiencies for MB and CR were slightly reduced from 90.76 % and 99.66 % to 88.08 % and 91.39 %, respectively, after 5 adsorption-desorption cycles, and the aerogel’s structural integrity was also maintained due to its good compressive strength (487.16 KPa). In addition, the adsorption mechanism of PCS aerogel was investigated using adsorption kinetics, isotherm, thermodynamics, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. It was proved that the adsorption process was endothermic spontaneous-monolayer adsorption driven by electrostatic attraction and hydrogen bonding. Therefore, the prepared biobased aerogel was expected to be a prospective material for removing mixed dyes from wastewater.

Hyaluronic acid-coated iron oxide nanoparticles for magnetic fluid hyperthermia and methylene blue dye removal: Preparation, physicochemical characterization, and enhancing the heating efficiency

We report here the magnetic fluid hyperthermia properties of water-dispersible hyaluronic acid-coated superparamagnetic iron oxide nanoparticles (HA-MNPs), prepared using the coprecipitation technique followed by ligand exchange. The presence of the hyaluronic acid coating is confirmed using Fourier transform infrared spectroscopy. Magneto-calorimetric studies show good field-induced heating efficiency of the HA-MNPs, where a high specific absorption rate (SAR) of ∼ 315 W/gFe is obtained for ∼ 5 wt% MNP concentration when exposed to an alternating magnetic field amplitude of ∼ 33.1 kA/m at ∼ 126 kHz. The heating efficiency is found to decrease by ∼ 33.8 % after immobilization of the MNPs within an agar matrix, which is attributed to the abrogation of Brownian relaxation. When subjected to an external DC magnetic field, the MNPs form linear chain-like structures, which causes the effective anisotropy energy density to increase. Magneto-calorimetric studies on agar-based oriented samples reveal a ∼ 19.5 % enhancement in SAR, thereby partly compensating for the loss in heating efficiency due to an increase in medium viscosity. The orientational ordering-induced enhancement in SAR is also verified using sweeping rate modified Stoner-Wohlfarth model-based calculations. In vitro cyto-toxicity studies on the HeLa cell lines reveal good cyto-compatibility of the MNPs. The negative charge on the surface of HA-coated MNPs is exploited to remove the cationic methylene blue dye from the aqueous medium, where the dye molecules are found to be physisorbed on the surface of the MNPs. The experimental findings clearly show the high induction heating efficiency, cyto-compatibility, and cationic dye-adsorption efficiency of the prepared HA-MNPs, thereby indicating the suitability of these MNPs for multi-functional applications like magnetic fluid hyperthermia and waste-water purification.

Multifunctional property of N,N-bis (carboxymethyl) glutamic acid modified biomass material: adsorption and degradation removals of cationic dyes in wastewater

As a common type of pollutants in industrial wastewater, cationic dyes have attracted great attentions. Using biodegradable N,N-di (carboxymethyl) glutamic acid (GLDA) as ligand and corn stalk (CS) as matrix, a novel and green biomass modified material GLDA-CS was successfully prepared. The multifunctional property of GLDA-CS for removing methylene blue (MB), malachite green (MG) and alkaline red 46 (R-46) from wastewater was evaluated. The dyes were removed by the electrostatic adsorption based on the cationic adsorption properties of GLDA-CS. The removal rates of MB, MG and R-46 can quickly reach 90.4%, 96.8% and 94.8% in short time. especially for MG and R-46 even only 20 min. The adsorption capacities of the dyes still remain more than 86.5% of the initial values after 5 cycles. In a heterogeneous system, the dyes were removed by Fenton-like degradation based on the metal chelating property of GLDA-CS. 100% degradation rates of the dyes can be achieved in 35 min under the acidic region. Even if at pH 7, degradation rates are 44.1%, 47.1% and 56.6% higher than those under the conventional homogeneous system, and the degradation rate remained at 83.7% after 5 cycles. Regardless of the adsorption or degradation, GLDA-CS shows strong anti-anion interference ability. The potential mechanisms of adsorption and degradation for the dyes by GLDA-CS were deduced by quantization calculation. It is concluded that the adsorption removal of the dyes by GLDA-CS follows MG > R-46 > MB, and mainly depends on the electrostatic interaction between -COOH in GLDA-CS and -N- in the dye molecules. Based on the degradation mechanism of Fenton-like reaction, the possible active sites of the dyes attacked by free radicals and their possible degradation intermediates were predicted by the calculations of Fukui function.

Selective adsorption of cationic dye by κ-carrageenan-potato starch bio-hydrogel: Kinetics, isotherm, and thermodynamic studies

An eco-friendly κ-carrageenan/potato starch bio-hydrogel is designed for the efficient removal of methylene blue (MB) dye from water. The incorporation of potato starch was successfully confirmed through XRD, FT-IR, and SEM analysis, while TGA highlighted the hydrogel's thermal stability. Batch adsorption experiments demonstrated excellent MB removal efficiency, with a maximum adsorption capacity of 116.1 mg/g under optimal conditions (initial dye concentration: 100 mg/L, contact time: 180 min, temperature: 20 °C, adsorbent dosage: 1.6 g/L, and pH: 11). FT-IR analysis indicated that electrostatic interactions and hydrogen bonding primarily govern the adsorption process. The adsorption followed pseudo-second-order kinetics and fitted well with the Langmuir isotherm model. Thermodynamic studies revealed that the adsorption was exothermic and spontaneous. A key feature of this bio hydrogel is its selective affinity for the cationic dye MB, in a mixture with Acid Orange (AO) and other cationic dyes (Rhodamine B (Rh B) and crystal violet (CV)). The adsorbent also demonstrated impressive reusability, maintaining 93 % of its efficiency after five cycles, highlighting its potential for sustainable and cost-effective water treatment.

Graphene oxide-polydopamine loaded uniform fibrous membranes via robust multi-channel microfluidic-electrospinning method

The rapid development of modern industries has caused serious water pollution such as dyes wastewater, which brings environmental problems and threatens human health. Thus, methods allowing efficient dyes removal from wastewater are substantially desirable. In this work, we fabricated graphene oxide-polydopamine (GO-PDA) by microfluidics, which enables rapid synthesis of products with excellent uniformity due to the precise control of reaction conditions. In addition, the GO-PDA/ thermoplastic polyurethane (GO-PDA/TPU) composite fibrous membrane was prepared in a high-efficiency manner by microfluidic electrospinning with a four-channel chip. Interestingly, GO-PDA not only improves the mechanical strength and hydrophilicity of the composite fibrous membrane, but also endows the membrane with efficient dye adsorption and separation capacity both for single and mixed dyes. It has been proved that the GO-PDA/TPU composite fibrous membrane exhibits selectivity towards cationic dyes, where the removal efficiency is up to 99 wt%. Moreover, the fibrous membrane could be utilized in a continuous and cyclic manner, which still maintains a high adsorption rate (>95 wt%) after 5 recycling, illustrating outstanding durability and reusability. This work proposes an efficient GO-PDA/TPU composite fibrous membrane towards selective adsorption of cationic dyes, which is of great significance in wastewater purification.

Cationic dye remediation in water treatment with Lizardite–Rice Husk composite: A statistical physics approach

This study presents the development of a novel composite adsorbent, Lizardite-Rice Husk Composite (LRHC), synthesized from lizardite, a mineral derived from chromite ore waste, and rice husk, an agricultural byproduct. The primary objective was to evaluate the efficiency of LRHC in the adsorption of cationic dyes, Malachite Green (MG) and Methylene Blue (MB), from aqueous solutions. Systematic investigations were conducted to assess the influence of adsorbent mass, initial dye concentration, stirring speed, and contact time on adsorption performance. The results revealed that LRHC exhibited optimal adsorption capacities at pH values above 5, with MB and MG adsorption capacities reaching 309.75 mg/g and 51.43 mg/g, respectively. Adsorption equilibrium for MB was achieved within 30 min, indicating rapid dye uptake. Isotherm analysis demonstrated that the Temkin model best described MB adsorption, while the Freundlich model was more suitable for MG, with favorable Langmuir constants. Kinetic studies confirmed that the adsorption followed a second-order model, suggesting chemisorption as the rate-determining step. Intraparticle diffusion and mass transfer were identified as significant contributors to the adsorption process. Thermodynamic studies indicated that MB adsorption was spontaneous (ΔG° = −4.69 kJ/mol for the concentration of 50 mg/L at 298 K) and that MG adsorption was non-spontaneous (ΔG° = 1.52 kJ/mol for the concentration of 50 mg/L at 298 K), with spontaneity increasing at higher initial concentrations. Statistical physics modeling, particularly the monolayer model, provided detailed insights into the adsorption mechanisms and geometry. Furthermore, LRHC demonstrated excellent reusability, maintaining over 80% of its initial adsorption capacity after four regeneration cycles via a heterogeneous Fenton-like reaction. The combination of easy availability, cost-effectiveness, and environmental friendliness makes LRHC a superior adsorbent for the removal of cationic dyes compared to conventional alternatives. This research contributes novel insights into the design and application of composite adsorbents, offering a sustainable solution for water treatment and addressing significant environmental challenges.

Two novel 3D polyoxometalate-based metal–organic frameworks for structure-directed selective adsorption and photodegradation of organic dyes

Degradation of organic dyes from industrial wastewater is crucial for human health and ecological balance. Synergy adsorption and photodegradation is one of the effective methods to degrade organic dyes at present. The former is usually limited by the challenge of its the recovery and the poor adsorption capacity of the adsorbent, whereas the latter frequently suffers from sluggish reaction kinetics. Herein, the introduction of the unique electron-rich Keggin polyoxometalates (CuW12 and SiW12) into electron-deficient metal photosensitive viologen framework to construct two polyoxometalate(POM)-based metal organic frameworks (POMOFs) of 3D porous layered structures, namely [Cu2(ipbp)2(H2O)2][CuW12O40]·3H2O (1) and [Co2(H2ipbp)3(H2O)2(CoO6)2][SiW12O40]·H2O (2); (H2ipbp·Cl = 1-(3,5-dicarboxyphenyl)-4,4′-bipyridinium), which enable selective adsorption of methylene blue (MB) and effectively photocatalytic degradation cationic dyes. In addition, POMs and metal-organic frameworks act in synergy to result in much improved adsorption of certain cationic dyes as well as enhanced photocatalytic activity that allow the catalyst to show better excellent reusability and stability. The adsorption degradation rate of MB and rhodamine B (RhB) of 2 is faster than that of 1 because of the lower Zeta potential of 2 suggesting that there are electrostatic interactions in the adsorption process. This work adopted a novel view to comprehening the technology.

Brazilian bentonite/MgO composites for adsorption of cationic and anionic dyes.

Industrial effluents, especially those containing dyes, have become the main cause of contamination of water resources. In this context, Brazilian bentonite/MgO composites, with excellent adsorptive properties, were prepared and investigated for their effectiveness in removing cationic and anionic dyes from aqueous solutions. The new adsorbents were obtained using Brazilian bentonites and MgO using the mechanochemical method followed by heat treatment (at 700°C for 4h). Different characterization techniques were used for the chemical, mineralogical, thermal, surface, and morphological analysis of the raw clays and the composites. The experimental adsorption isotherms were quantified under different conditions of initial concentration, contact time, pH, adsorbent dosage, and temperature variation to interpret the adsorption mechanism of the crystal violet (CV) and Congo red (CR) dyes. The modeling results were obtained from the empirical Sips equation and Pseudo Second Order (PSO) kinetics, indicating that the adsorption of molecules is a heterogeneous phenomenon that occurs in a monolayer on the surface (ns > 1), with the adsorption rate determined by chemisorption. The composites showed the best removal efficiency performance compared to the raw bentonites, with an increase of 12% for the CV dye and 46% for the CR dye. In addition, the qmax values obtained were 423.02mg/g and 479.86mg/g (AM01). This research underscores the potential of Brazilian bentonite/MgO composites as a promising solution for the removal of cationic and anionic dyes from water, offering hope for future applications in the field of environmental engineering and materials science.

Organo cationic dyes adsorption on charged nano-clay: Revealing dual mechanisms through GCS modeling and DFT molecular simulations

This study investigates the adsorption mechanisms of organic cationic dyes, specifically malachite green (MG) and toluidine blue (TB), on sodium montmorillonite clay (Na-MMC). Using montmorillonite sourced from the Nador deposit in Northern Morocco, we aim to model cation exchange with the Gouy-Chapman-Stern (GCS) model. The adsorption capacities are found to be 192.5 meq/100 g for TB and 175.8 meq/100 g for MG at room temperature and uncontrolled pH. X-ray diffraction (XRD) analysis was employed to determine the interlayer spacing of the montmorillonite, contributing to the understanding of adsorption mechanisms. GCS modeling provided insight into the adsorption constants for both dyes, alongside parameters related to the solid/solution interface such as the amount adsorbed per layer, ion concentration in the solution, and clay surface potential. These findings confirmed a significant affinity between the dyes and the clay, aligning with the literature. Moreover, Density Functional Theory (DFT) simulations indicated a stronger affinity of toluidine blue for negatively charged surfaces compared to other dyes.

Graphene Oxide Decorated with Nickel Cobaltite Nanoparticles as an Adsorbent for Cationic Methyl Green Dye: Kinetic, Isotherm, and Thermodynamic Studies

‎تم في هذه الدراسة ، تزيين ‏رقائق أكسيد الجرافين (‏GO‏) بجسيمات ‏كوبلتيت النيكل النانوية ‏NiCo2O4‎‏(‏NC‏) عن طريق الترسيب في ‏الموقع ، وتم استخدام المتراكب ‏المحضر (‏NC: GO‏) كسطح ماز لإزالة ‏صبغة الميثيل الخضراء ( ‏MG‏) من ‏المحاليل المائية. تم التحقق من ‏التغطية الناجحة لأوكسيد الجرافين ‏بجزيئات كوبلتيت النيكل النانوية ‏‏(‏NC‏) باستخدام دراسات ‏FT-IR‏ وحيود ‏الأشعة السينية (‏XRD‏). كانت أحجام ‏الجسيمات البلورية لل ‏NC‏ و ‏ لل ‏GO‏ المزين ب NCهي ‏‎10.53‎‏ نانوميتر ‏‏9.30 نانومتر على التوالي. تم دراسة ‏تأثير العديد من العوامل التجريبية ‏، بما في ذلك زمن التلامس ، وكمية ‏السطح الماز ، ودرجة الحرارة. كان ‏وقت التلامس الأمثل وكمية السطح 120 ‏دقيقة و 3 مجم / لتر على التوالي. ‏تتلائم بيانات الامتزاز بشكل أفضل مع ‏ايزوثيرم ‏Freundlich‏. تم استخدام ‏أربعة نماذج حركية لتتبع عملية ‏الامتزاز: معادلة زائفة من الدرجة ‏الأولى ، ومعادلة زائفة من الدرجة ‏الثانية ، ومعادلة الانتشار داخل ‏الجسيمات ، ومعادلة بويد. أظهرت ‏نمذجة البيانات التجريبية أن حركية ‏الامتزاز كانت ممثلة بشكل جيد ‏بنموذج الرتبة الثانية الزائفة (‏R2 ‎‎= 0.9945‎‏) مع معدل ثابت سرعة يبلغ 3.2 ‏‏× 10 - 3 (جم / مجم. دقيقة). يتم ‏امتصاص صبغة ‏MG‏ تدريجيًا بواسطة ‏الجسيمات النانوية ‏NC‏ من خلال ‏الانتشار داخل الجسيمات ويتم ‏الاحتفاظ بها بعد ذلك في مسام أصغر. ‏أظهرت قيم التحليل الديناميكي ‏الحراري أن عملية امتزاز صبغة ‏MG‏ ‏كانت ماصة للحرارة بطبيعتها ، و ‏تلقائية وعملية الامتزاز فيزيائية. الكلمات المفتاحية: الانتشار داخل الجسيمات ، المسافات البينية، النموذج الزائف من الدرجة الأولى ، معادلة بويد

Corn Husk‐Derived Carbon Fused with Iron Oxide as Adsorbent for Cationic Dyes

AbstractThe development of nanomaterials for dye degradation has garnered significant interest due to their efficiency, environmental benefits, and cost‐effectiveness. In this study, a nanocomposite adsorbent composed of α‐Fe2O3 coupled with carbon derived from eco‐friendly corn husk has been developed. This material effectively captured cationic dyes, Methylene Blue (MB) and Malachite Green (MG), from aqueous solutions, including industrial dye effluent from local industry. The synthesized nanocomposite demonstrated rapid removal of MB and MG from the solution without the need for additional oxidizing or reducing agents. The adsorption conditions by varying parameters such as adsorbent dose, contact time, solution pH, initial dye concentration, and temperature have been optimized. Adsorption isothermal studies indicated that the Langmuir isotherm model best explained the adsorption process. Kinetic studies revealed that the adsorption process follows a pseudo‐first‐order model for MB, while the intraparticle diffusion model is more appropriate for MG. Moreover, the nanocomposite exhibited excellent reusability and regenerability for dye adsorption. Our study showcases the effectiveness of the synthesized nanocomposite adsorbent, comprising α‐Fe2O3 integrated with carbon derived from eco‐friendly corn husk using a simple and sustainable methodology, in efficiently removing cationic dyes from textile wastewater. This approach offers a promising solution for environmental remediation.

Highly Reusable Nano Adsorbent Based on Clay-Incorporated Hydrogel Nanocomposite for Cationic Dye Adsorption

Highly Reusable Nano Adsorbent Based on Clay-Incorporated Hydrogel Nanocomposite for Cationic Dye Adsorption

Green, sustainable and eco-friendly approach for extraction of silica nanoparticles from Ananas comosus and Saccharum ravannae: a comparative study of dye removal from aqueous solution

ABSTRACT Silica nanoparticles (SiNPs) were extracted in an eco-friendly manner from the crown of Ananas comosus (pineapple, AC SiNPs) and leaves of Saccharum ravannae (weed grass, SR SiNPs). Initial studies were performed to examine the adsorption of various cationic (Methylene blue, MB; Safranin, SA), anionic (Trypan Blue, TB; Eosin yellow, EY), and neutral dyes (Neutral red, NR). The investigation revealed that the maximum removal was achieved at an adsorbent dose of 1 g L−1 at an optimum pH of 7–8, at an equilibrium contact time of ∼15 mins for the dye concentration of 10 mg L−1 at 298 K. Adsorption followed the pseudo-second-order kinetic model and Freundlich isotherm model, indicating multi-layered heterogeneous adsorption. The maximum adsorption capacity (qmax) for MB, SA, and NR was found to be 81.3 mg g−1, 21.74 mg g−1, and 24.75 mg g−1 respectively, for AC SiNPs. The qmax for SR SiNPs was found to be 78.12 mg g−1, 47 mg g−1, and 70 mg g−1 for MB, SA, and NR respectively. Moreover, desorption studies showed that till 4–5 cycles, >90% of the removal efficiency was retained. Thus, the biogenic and non-toxic SiNPs can be a greener, eco-friendly alternative material for dye removal from wastewater.

Sustainable synthesis of carbide slag waste derived hydroxyapatite and its application for cationic dye adsorption

Hydroxyapatite (HAp) and its composites have gained significant recognition as an effective biocompatible adsorbent for a variety of pollutants, attributed to its extensive surface area, robust chemical and thermal stability, and non-toxic nature. Yet, its industrial-scale application is obstructed by the cost of synthesis. This study investigates the sustainable and cost-effective route of HAp synthesis using carbide slag waste. The carbide slag-derived hydroxyapatite (CS-HAp) is synthesized via a two-step neutralization method at ambient conditions by employing carbide slag waste as an eco-friendly calcium source. The thorough characterization of CS-HAp revealed a favorable Ca/P ratio of 1.86 with adequate structural and thermal properties. The prepared CS-HAp is proposed as an economical adsorbent by employing it for the removal of model pollutant methylene blue (MB) dye from an aqueous solution. Batch adsorption experiments assessed the influence of operational parameters such as initial dye concentration, initial pH, contact time, and adsorbent dose on MB removal. The adsorption kinetics were best described by the pseudo-second-order model with an equilibrium adsorption capacity of 36 mg/g close enough to the actual equilibrium adsorption capacity of 32 mg/g. The Freundlich isotherm model adequately represented the adsorption isotherms with R2 of 0.9712, indicating a multilayer adsorption process.

Fabricating whole pine needles biomass with phenylhydrazine-4-sulphonic acid for effective removal of cationic dyes and heavy metal ions from wastewater

We applied a holistic, sustainable, and green approach to develop an effective multipurpose adsorbent from whole pine needles (PNs), a forest waste lignocellulosic biomass. The PNs were oxidized and modified with phenylhydrazine-4-sulphonic acid (ɸHSO3H) to OPN-ɸHSO3H. The latter was characterized and tested as an adsorbent for cationic dyes, malachite green (MG), methylene blue (MB), crystal violet (CV), and metal ions (Hg2⁺ and Pb2⁺). The adsorption followed different kinetic models: Elovich for MG and MB, pseudo-second-order for CV, and pseudo-first-order for Hg2⁺ and Pb2⁺. Langmuir isotherm indicated maximum adsorption capacities of 303.4 ± 8.91 mgg−1 (MG), 331.4 ± 17.50 mgg−1 (MB), 376.6 ± 22.47 mgg−1 (CV), 210.8 ± 28.86 mgg−1 (Hg2⁺), and 172.9 ± 20.93 mgg−1 (Pb2⁺) within 30 min. Maximum removal efficiencies were 99.0% (MG), 98.0% (MB), 96.04% (CV), 95.5% (Hg2⁺), and 89.8% (Pb2⁺). The adsorbent demonstrated significant regeneration and reusability over ten cycles, proving highly efficient for both cationic dyes and metal ions, with wide potential for practical applications where more than one adsorbate is present.