Batch Adsorption Studies on the Removal of Acid Blue 25 from Aqueous Solution Using Azolla pinnata and Soya Bean Waste

Adsorption Behavior and Dynamic Interactions of Anionic Acid Blue 25 on Agricultural Waste

In this study, adsorption characteristics of a negatively charged dye, Acid Blue 25 (AB25), on pomelo pith (PP) was studied by varying the adsorption parameters, with the aim of evaluating the adsorption mechanism and establishing the role of hydrogen bonding interactions of AB25 on agricultural wastes. The kinetics, intraparticle diffusion, mechanism, and thermodynamics of the AB25 adsorption were systematically evaluated and analyzed by pseudo-first-order and pseudo-second-order kinetic models, the Weber-Morris intraparticle and Boyd mass transfer models, the Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherm models, and the Van't Hoff equation. It was found that AB25 adsorption followed pseudo-second-order kinetics, governed by a two-step pore-volume intraparticle diffusion of external mass transfer of AB25 onto the PP surface. The adsorption process occurred spontaneously. The adsorption mechanism could be explained by the Langmuir isotherm model, and the maximum adsorption capacity was estimated to be 26.9 mg g-1, which is comparable to many reported adsorbents derived from agricultural wastes. Changes in the vibrational spectra of the adsorbent before and after dye adsorption suggested that AB25 molecules are bound to the PP surface via electrostatic and hydrogen bonding interactions. The results demonstrated that the use of pomelo pith, similar to other agricultural wastes, would provide a basis to design a simple energy-saving, sustainable, and cost-effective approach to remove negatively charged synthetic dyes from wastewater.

Pollutant removal from dairy wastewater using live Azolla filiculoides in batch and continuous bioreactors

Fast and proper treatment of dairy wastewater is necessary before discharging it to the environment. In this study, healthy Azolla filiculoides was used to remove pollutants, including phosphorus (P), sodium (Na), chemical oxygen demand (COD), biological oxygen demand (BOD), and total dissolved solids (TDS) of dairy effluent in batch, continuous system, as well as continuous with the slow stirring system. These systems were handmade. The maximum removal efficiency was related to the P, which obtained 66.25% after 12 h in the batch bioreactor system. The highest removal of 13.69% after 21 h was obtained for Na using continuous with a slow stirring method. The highest removal related to the COD and BOD was 33.53% and 29.93% after 18 h, respectively, in continuous with the slow stirring system. TDS removal was achieved 31.44% after 24 h using the batch system. The results of these three systems were compared with each other using a one-way analysis of variance (ANOVA). There was no significant difference between them. Azolla filiculoides is an abundant plant in northern nature that a biosystem was used for optimum usage. It can be used as an efficient, inexpensive, and affordable bioadsorbent for dairy wastewater treatment. PRACTITIONER POINTS: Live Azolla filiculoides was used to remove pollutants. P, Na, BOD, COD, and TDS were removed from dairy wastewater. Batch, continuous, and continuous with the slow stirring systems were used. Live Azolla was an efficient, inexpensive, and affordable bio-adsorbent for dairy wastewater treatment.

A Facile Synthesis of Bi2O3/CoFe2O4 Nanocomposite with Improved Synergistic Photocatalytic Potential for Dye Degradation

Semiconductor-based photocatalysis is a probable approach to overcoming many pollution problems and eradicating toxic organic materials from wastewater. This research endeavor aimed to explore the synergistic potential of different semiconductor nanocomposites for photocatalytic degradation of organic pollutants in contaminated water. A facile hydrothermal approach was employed to synthesize bismuth oxide and cobalt ferrite nanoparticles from their precursors—bismuth nitrate pentahydrate, ferric chloride hexahydrate and cobalt chloride hexahydrate—with various concentrations and conditions to optimize the product. Subsequently, nanocomposites of bismuth oxide and cobalt ferrite were prepared by solid-state mixing in varying concentrations followed by calcination. UV/visible diffuse reflectance spectroscopy, X-ray diffraction, scanning electron microscopy and elemental dispersive X-ray spectroscopic techniques have corroborated the successful synthesis of nanocomposites. The energy gaps of bismuth oxide and cobalt ferrite nanocomposites were computed in the range of 1.58–1.62 eV by Tauc plots. These nanocomposite materials were ascertained for photocatalytic potential to degrade methyl orange organic dye in water. A nanocomposite with equiquantic proportions has shown the best photocatalytic degradation activity, which may be attributed to the type-II band configuration and a synergistic effect, because Bi2O3 acts as an electron sink. This synergism has reduced the cogent band gap, hindered electron hole recombination and increased electron hole availabilities for photodegradation reactions, thus ensuing an efficient photodegradation co-work of Bi2O3/CoFe2O4 nanocomposites.

Enhanced adsorption of acid Blue-25 dye onto chitosan/porous carbon composite modified in 1-allyl-3-methyl imidazolium bromide ionic liquid

In this study, chitosan/porous carbon composite (C-PC) modified in 1-Allyl-3-methyl imidazolium bromide [AMIM][Br] under airtight condition was prepared for the removal of Acid Blue-25 dye (AB-25) from aqueous medium. For comparison of adsorption efficiency of C-PC, chitosan-activated carbon composite (C-AC) was also prepared in 1% acetic acid. The adsorbents were characterised using SEM, EDX, XRD, BET, TGA and FTIR. The micrograph of C-PC revealed cavities and slightly rough surfaces dominated with similar sized and irregular shaped stone-like materials which differ from the precursors' micrograph. BET analysis revealed the domination of mesopores on the C-PC and C-AC surfaces, as the hydroxyl and amino group on C-PC are the main active sites for AB-25 dye uptake. The dye was better adsorbed onto C-PC at pH 2 and C-AC at pH 4. The adsorption capacity obtained for C-PC, C-AC, activated carbon (AC) and chitosan (CH) using Langmuir isotherm model are 3333.33 mg/g, 909.90 mg/g, 909.09 mg/g and 833.33 mg/g, respectively. The experimental data are well described by Langmuir and Fruendlich isotherms for adsorption of the dye onto C-PC, AC and CH. C-AC fitted into Langmuir isotherm only. The kinetics of the adsorption fitted into pseudo-second order indicating the possibility of chemical interactions in the adsorption process.

Removal of Fluorescein Dye from Aqueous Solutions Using Natural and Chemically Treated Pine Sawdust

The various factors affecting the removal of fluorescein dye using sawdust from aqueous solutions such as time, initial concentration, pH, and temperature were studied. The optimal conditions for removing the FD are 1 g of sawdust at pH 3 and 120 min time of contact. Dye removal dropped from 93.42% to 80.04% with natural pine sawdust (NPS) and from 96.83% to 81.51% with synthetic pine sawdust (SPS) by increasing their concentration from 2 to 10 mg/L. Isotherm, kinetic, and thermodynamic models were applied for determining their constants. The results indicated that the FD removal equilibrium was effectively defined by the Langmuir, Freundlich, and Temkin models. Kinetic studies showed that the pseudo-second order was well suited for dye removal, and the internal diffusion process was by two steps. The thermodynamic parameter values suggested that FD removal were physical adsorption, exothermic, lower randomness, and spontaneous.

Preparation and characterization of Chicory leaf powder and its application as a nano-native plant sorbent for removal of Acid Blue 25 from aqueous media: isotherm, kinetic and thermodynamic study of the adsorption phenomenon

In this study, the Chicory leaf powder (CLP) was used as a native adsorbent to eliminate the Acid Blue 25 dye from aqueous media. The prepared native adsorbent was characterized by several techniques including the X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform spectroscopy (FTIR), Brunauer–Emmet–Teller essay (BET), and particle size analyzer (PSA). A collection of experiments was performed to distinguish the optimal conditions and to probe the effects of the different parameters such as initial concentration, contact time, adsorbent dosage, pH of solution, and temperature on the sorbent capacity. The attained optimal conditions for removal the Acid Blue 25 dye were pH = 3–4, contact time 50 min, dosage 0.1 g, and initial concentrations 10 (mg/L) at 30 °C. The adsorption data revealed that the adsorption procedure has more match with the Langmuir isotherm than others. The kinetic data were better fitted with the pseudo-second-order pattern with a trusty correlation coefficient. Finally, the thermodynamic parameters illustrated that the adsorption process is exothermal and spontaneous. Based on magnitude of the standard enthalpy change related to the studied adsorption, we may derive that the considered adsorption is physical adsorption.

Effect of Ammonia Modification on Activated Carbons for the Removal of Acidic Anthraquinone Dyes

The objective of this research is to study the retention of two acidic anthraquinone dyes by Coconut-shell-based activated carbon. Ultimately, this work allows the valorization of this new material as an adsorbent. The effect of ammonia modification on the adsorption capacity of activated carbon towards remazol brilliant blue R19 (RB19) and acid blue 25 (AB25), has been studied. Coconut-shell-based activated carbon material was modified under ammonia flow at 900 and 1000 °C. The adsorption rates and isotherms of RB19 and AB25 on the resultant materials were then tested. The results show that ammonia modification remarkably increases the adsorption capacities of the activated carbons to RB19 and AB25, by a factor of 2–3 after treatment at 1000 °C (From 0.22 mmol g−1 and 1.04 mmol g−1 to 0.76 mmol g−1 and 2.19 mmol g−1 on AC and AC-O-N-1000, respectively). The increased adsorption capacity is attributed to the introduction of basic nitrogen-containing functional groups and enhanced pore development by ammonia modification. The collected experimental kinetic and isotherm data are well compatible with the intraparticle diffusion kinetic model and the Langmuir isotherm model. According to these results, the adsorption affinity is homogeneous in terms of surface functional groups and the surface bears a finite number of identical adsorption sites.

Phytoextraction potential of water fern (Azolla pinnata) in the removal of a hazardous dye, methyl violet 2B: Artificial neural network modelling

This study investigated the potential of Azolla pinnata (AP) in the removal of toxic methyl violet 2B (MV) dye wastewater using the phytoextraction approach with the inclusion of an Artificial Neural Network (ANN) modelling. Parameters examined included the effects of dye concentration, pH and plant dosage. The highest removal efficiency was 93% which was achieved at a plant dosage of 0.8 g (dye volume = 200 mL, initial pH = 6.0, initial dye concentration = 10 mg L^-1). A significant decrease in relative frond number (RFN), a growth rate estimator, observed at a dye concentration of 20 mg L^-1 MV indicated some toxicity, which coincided with the plant pigments studies where the chlorophyll a content was lower than the control. There were little differences in the plant pigment contents between the control and those in the presence of dye (5 to 15 mg L^-1) indicating the tolerance of AP to MV at lower concentrations. A three-layer ANN model was optimized (6 neurons in the hidden layer) and successfully predicted the phytoextraction of MV (R = 0.9989, RMSE = 0.0098). In conclusion, AP proved to be a suitable plant that could be used for the phytoextraction of MV while the ANN modelling has shown to be a reliable method for the modelling of phytoextraction of MV using AP.

Green synthesis of graphene from recycled PET bottle wastes for use in the adsorption of dyes in aqueous solution

Polyethyleneterephthalate (PET) is an important component of post-consumer plastic waste. This study focuses on the potential of utilizing "waste-treats-waste" by synthesis of graphene using PET bottle waste as a source material. The synthesized graphene is characterized by SEM, TEM, BET, Raman, TGA, and FT-IR. The adsorption of methylene blue (MB) and acid blue 25 (AB25) by graphene is studied and parameters such as contact time, adsorbent dosage were optimized. The Response Surface Methodology (RSM) is applied to investigate the effect of three variables (dye concentration, time and temperature) and their interaction on the removal efficiency. Adsorption kinetics and isotherm are followed a pseudo-second-order model and Langmuir and Freundlich isotherm models, respectively. Thermodynamic parameters demonstrated that adsorption of dye is spontaneous and endothermic in nature. The plastic waste can be used after transformation into valuable carbon-based nanomaterials for use in the adsorption of organic contaminants from aqueous solution.