Functionalized locust bean pod (Parkia biglobosa) activated carbon for Rhodamine B dye removal

Zinc oxide decorated plantain peel activated carbon for adsorption of cationic malachite green dye: Mechanistic, kinetics and thermodynamics modeling

Reports have shown that malachite green (MG) dye causes various hormonal disruptions and health hazards, hence, its removal from water has become a top priority. In this work, zinc oxide decorated plantain peels activated carbon (ZnO@PPAC) was developed via a hydrothermal approach. Physicochemical characterization of the ZnO@PPAC nanocomposite with a 205.2 m2/g surface area, porosity of 614.68 and dominance of acidic sites from Boehm study established the potency of ZnO@PPAC. Spectroscopic characterization of ZnO@PPAC vis-a-viz thermal gravimetric analyses (TGA), Fourier Transform Infrared Spectroscopy (FTIR), Powdered X-ray Diffraction (PXRD), Scanning Electron Microscopy and High Resolution - Transmission Electron Microscopy (HR-TEM) depict the thermal stability via phase transition, functional group, crystallinity with interspatial spacing, morphology and spherical and nano-rod-like shape of the ZnO@PPAC heterostructure with electron mapping respectively. Adsorption of malachite green dye onto ZnO@PPAC nanocomposite was influenced by different operational parameters. Equilibrium data across the three temperatures (303, 313, and 323 K) were most favorably described by Freundlich indicating the ZnO@PPAC heterogeneous nature. 77.517 mg/g monolayer capacity of ZnO@PPAC was superior to other adsorbents compared. Pore-diffusion predominated in the mechanism and kinetic data best fit the pseudo-second-order. Thermodynamics studies showed the feasible, endothermic, and spontaneous nature of the sequestration. The ZnO@PPAC was therefore shown to be a sustainable and efficient material for MG dye uptake and hereby endorsed for the treatment of industrial effluent.

Innovations in metal-organic frameworks (MOFs): Pioneering adsorption approaches for persistent organic pollutant (POP) removal

Adsorption is a promising way to remove persistent organic pollutants (POPs), a major environmental issue. With their high porosity and vast surface areas, MOFs are suited for POP removal due to their excellent adsorption capabilities. This review addresses the intricate principles of MOF-mediated adsorption and helps to future attempts to mitigate organic water pollution. This review examines the complicated concepts of MOF-mediated adsorption, including MOF synthesis methodologies, adsorption mechanisms, and material tunability and adaptability. MOFs' ability to adsorb POPs via electrostatic forces, acid-base interactions, hydrogen bonds, and pi-pi interactions is elaborated. This review demonstrates its versatility in eliminating many types of contaminants. Functionalizing, adding metal nanoparticles, or changing MOFs after they are created can improve their performance and remove contaminants. This paper also discusses MOF-based pollutant removal issues and future prospects, including adsorption capacity, selectivity, scale-up for practical application, stability, and recovery. These obstacles can be overcome by rationally designing MOFs, developing composite materials, and improving material production and characterization. Overall, MOF technology research and innovation hold considerable promise for environmental pollution solutions and sustainable remediation. Desorption and regeneration in MOFs are also included in the review, along with methods for improving pollutant removal efficiency and sustainability. Case studies of effective MOF regeneration and scaling up for practical deployment are discussed, along with future ideas for addressing these hurdles.

Rhodamine B, an organic environmental pollutant induces reproductive toxicity in parental and teratogenicity in F1 generation in vivo

This study investigated the reproductive toxicity of rhodamine B in zebrafish and its transgenerational effects on the F1 generation. In silico toxicity predictions revealed high toxicity of rhodamine B, mainly targeting pathways associated with the reproductive and endocrine systems. In vivo experiments on zebrafish demonstrated that rhodamine B exposure at a concentration of 1.5 mg/L led to significant impairments in fecundity parameters, particularly affecting females. Histopathological analysis revealed distinct changes in reproductive organs, further confirming the reproductive toxicity of rhodamine B, with females being more susceptible than males. Gene expression studies indicated significant suppression of genes crucial for ovulation in rhodamine B-treated female fish, highlighting hormonal imbalance as a potential mechanism of reproductive toxicity. Furthermore, bioaccumulation studies showed the presence of rhodamine B in both adult fish gonads and F1 generation samples, suggesting transgenerational transfer of the dye. Embryotoxicity studies on F1 generation larvae demonstrated reduced survival rates, lower hatching rates, and increased malformations in groups exposed to rhodamine B. Moreover, rhodamine B induced oxidative stress in F1 generation larvae, as evidenced by elevated levels of reactive oxygen species and altered antioxidant enzyme activity. Neurotoxicity assessments revealed reduced acetylcholinesterase activity, indicating potential neurological impairments in F1 generation larvae. Additionally, locomotory defects and skeletal abnormalities were observed in F1 generation larvae exposed to rhodamine B. This study provides comprehensive evidence of the reproductive toxicity of rhodamine B in adult zebrafish and its transgenerational effects on the F1 generation.

A review on sustainable management of biomass: physicochemical modification and its application for the removal of recalcitrant pollutants-challenges, opportunities, and future directions

Adsorption is one of the most efficient methods for remediating industrial recalcitrant wastewater due to its simple design and low investment cost. However, the conventional adsorbents used in adsorption have several limitations, including high cost, low removal rates, secondary waste generation, and low regeneration ability. Hence, the focus of the research has shifted to developing alternative low-cost green adsorbents from renewable resources such as biomass. In this regard, the recent progress in the modification of biomass-derived adsorbents, which are rich in cellulosic content, through a variety of techniques, including chemical, physical, and thermal processes, has been critically reviewed in this paper. In addition, the practical applications of raw and modified biomass-based adsorbents for the treatment of industrial wastewater are discussed extensively. In a nutshell, the adsorption mechanism, particularly for real wastewater, and the effects of various modifications on biomass-based adsorbents have yet to be thoroughly studied, despite the extensive research efforts devoted to their innovation. Therefore, this review provides insight into future research needed in wastewater treatment utilizing biomass-based adsorbents, as well as the possibility of commercializing biomass-based adsorbents into viable products.

Thermally modified nanocrystalline snail shell adsorbent for methylene blue sequestration: equilibrium, kinetic, thermodynamic, artificial intelligence, and DFT studies

In recent years, the quest for an efficient and sustainable adsorbent material that can effectively remove harmful and hazardous dyes from industrial effluent has become more intense. The goal is to explore the capability of thermally modified nanocrystalline snail shells (TMNSS) as a new biosorbent for removing methylene blue (MB) dye from contaminated wastewater. TMNSS was employed in batch adsorption experiments to remove MB dye from its solutions, taking into account various adsorption parameters such as contact time, temperature, pH, adsorbent dosage, and initial concentration. SEM, EDS, XRD, and FTIR were used to characterize the adsorbent. The study further developed and adopted adaptive neuro-fuzzy inference system (ANFIS) and density functional theory (DFT) studies to holistically examine the adsorption process of MB onto the adsorbent. EDX and FTIR confirm the formation of CaO with a sharp peak at 547 cm-1, and C-O and O-H are present, as well. SEM and XRD show an irregularly shaped highly crystalline nanosized (65 ± 2.81 nm) particle with a lattice parameter value of 8.611617 Å. The adsorption efficiency of 96.48 ± 0.58% was recorded with a pH of 3.0 and an adsorbent dose of 10 mg at 30 °C. The findings from the study fit nicely onto Freundlich isotherms, with Qm = 31.7853 mg g-1 and R2 = 0.9985. Pseudo-second-order kinetics recorded the least error value of 0.8792 and R2 = 0.9868, thus indicating chemisorption and multilayer adsorption processes. The exothermic and spontaneous nature of the adsorption process are demonstrated by ΔH° and ΔG°. The performance of the ANFIS-based prediction of removal rate, which was demonstrated by a root mean square error (RMSE) value of 2.2077, mean absolute deviation (MAD) value of 1.1429, mean absolute error (MAE) value of 1.8786, and mean absolute percentage error (MAPE) value of 2.0178, revealed that the ANFIS model predictions and experimental findings are in good agreement. More so, DFT provides insights into the molecular interactions between MB and the adsorbent surface, with a calculated adsorbate-adsorbent binding affinity value of -1.3 kcal mol-1, thus confirming the ability of TMNSS for MB sequestration. The findings of this study highlight the promising potential of thermally modified nanocrystalline snail shells as sustainable and efficient adsorbents for MB sequestration.

In-situ biofabrication of bacterial nanocellulose (BNC)/graphene oxide (GO) nano-biocomposite and study of its cationic dyes adsorption properties

In the present study, bacterial nanocellulose/graphene oxide nano-biocomposites (BNC-GO-NBCs) were fabricated by Komagataeibacter saccharivorans NUWB1 using an in-situ method involving three time-dependent approaches. Physicochemical studies showed that the chosen dried BNC-GO-NBC possessed a three-dimensional interconnected porous structure of BNC with GO layers embedded within the BNC fibrils. BNC-GO-NBC had a crystallinity index of 74.21 %, higher thermostability up to 380 °C and could withstand a tensile load of 84.72 MPa. N2 adsorption-desorption isotherm of the BNC-GO-NBC was found to be of type IV, suggesting a mesoporous type structure with a total pore volume and surface area of 6.232e-04 cc g-1 and 10.498 m2. BNC-GO-NBC exhibited remarkable adsorption capacity for two cationic dyes, Rhodamine B (RhB) and Acridine Orange (AO), and the adsorption data conformed well to the Langmuir isotherm (R2 = 0.99) and pseudo-second-order model. Thermodynamic studies indicated that the adsorption process was spontaneous and endothermic. Additionally, the BNC-GO-NBC displayed the potential for regeneration, with the ability to be recycled up to five times. Further, the antibacterial activity, cell cytotoxicity and oxidative stress assays of the BNC-GO-NBC revealed its non-cytotoxic nature. The findings of the present investigation evidently suggest the potentiality of BNC-GO-NBC in the application of dye adsorption and other environmental applications.

Upcycling fish scales through heating for steganography and Rhodamine B adsorption application

With increasing population and limited resources, a potential route for improving sustainability is increased reuse of waste materials. By re-looking at wastes, interesting properties and multifunctionalities can be discovered in materials previously explored. Despite years of research on bio-compatible fish scales, there is limited study on the fluorescence property of this abundant waste material. Controlled denaturation of collagen and introduction of defects can serve as a means to transform the fluorescence property of these fish scale wastes while providing more adsorption sites for pollutant removal, turning multifunctional fish scales into a natural steganographic material for transmitting text and images at both the macroscopic and microscopic levels and effectively removing Rhodamine B pollutants (91 % removal) within a short contact time (10 minutes). Our work offers a glimpse into the realm of engineering defects-induced fluorescence in natural material with potential as bio-compatible fluorescence probes while encouraging multidimensional applicability to be established in otherwise overlooked waste resources.

Removal of Methylene Blue and Methyl Red from Aqueous Solutions Using Activated Carbons Obtained by Chemical Activation of Caraway Seed

In this study, activated carbons were produced through the chemical activation of caraway seeds using three different activators: Na2CO3, K2CO3, and H3PO4. A 1:2 weight ratio of precursor to activator was maintained in every instance. Comprehensive analyses were conducted on the resultant activated carbons, including elemental analysis, textural parameters determination, Boehm titration for surface oxygen functional groups, pH assessment of aqueous extracts, and quantification of ash content. The produced materials were subjected to adsorption tests for methylene blue and methyl red sodium salt from the liquid phase and the effects of adsorbent dosage, pH of the aqueous dye solution, process temperature, and adsorbent-adsorbate contact time on sorption capacity obtained. To characterize the adsorption model of the examined pollutants, both the Langmuir and Freundlich equations were employed. In addition, the sorption capacity of the obtained carbon materials against an iodine aqueous solution was assessed. The specific surface area of the obtained adsorbents ranged from 269 to 926 m2/g. By employing potassium carbonate to chemically activate the starting substance, the resulting activated carbons show the highest level of specific surface area development and the greatest sorption capacity against the tested impurities-296 mg/g for methylene blue and 208 mg/g for methyl red sodium salt. The adsorption rate for both dyes was determined to align with a pseudo-second-order kinetic model. The experimental adsorption data for methylene blue were well-described by the Langmuir model, whereas the Freundlich model was found to be congruent with the data pertaining to methyl red sodium salt.

Black carbon derived PET plastic bottle waste and rice straw for sorption of Acid Red 27 dye: Machine learning approaches, kinetics, isotherm and thermodynamic studies

This study focuses on the probable use of PET waste black carbon (PETWBC) and rice straw black carbon (RSBC) as an adsorbent for Acid Red 27 (AR 27) adsorption. The prepared adsorbent is characterized by FE-SEM and FT-IR. Batch adsorption experiments were conducted with the influencing of different operational conditions namely time of contact (1-180 min), AR 27 concentration (5-70 mg/L), adsorbent dose (0.5-20 g/L), pH (2-10), and temperature (25-60°C). High coefficient value [PETWBC (R2 = 0.94), and RSBC (R2 = 0.97)] of process optimization model suggesting that this model was significant, where pH and adsorbent dose expressively stimulus removal efficiency including 99.88, and 99.89% for PETWBC, and RSBC at pH (2). Furthermore, the machine learning approaches (ANN and BB-RSM) revealed a good association between the tested and projected value. Pseudo-second-order was the well-suited kinetics, where Freundlich isotherm could explain better equilibrium adsorption data. Thermodynamic study shows AR 27 adsorption is favourable, endothermic, and spontaneous. Environmental friendliness properties are confirmed by desorption studies and satisfactory results also attain from real wastewater experiments. Finally, this study indicates that PETWBC and RSBC could be potential candidates for the adsorption of AR 27 from wastewater.

Removal of hazardous textile dye from simulated wastewater by municipal organic solid waste charcoal using machine learning approaches: Kinetics, isotherm, and thermodynamics

This study focuses on the probable use of municipal organic solid waste charcoal (MOSWC) as an adsorbent for Methyl orange (MO) adsorption. The prepared MOSWC is characterized by FE-SEM and FT-IR. Batch adsorption experiments were conducted with the influencing of different operational conditions namely time of contact (1-180 min), adsorbate concentration (60-140 mg/L), adsorbent dose (1-5 g/L), pH (3-11), and temperature (25-60 °C). The high coefficient value (R2 = 0.96) of the process optimization model suggests that this model was significant, where pH and adsorbent dose expressively stimulus adsorption efficiency including 40.11 mg/g at pH (3), MO concentration (100 mg/L), and MOSWC dose (1 g/L). Furthermore, the machine learning approaches (ANN and BB-RSM) revealed a good association between the tested and projected values. The highest monolayer adsorption capacity of MO was 90.909 mg/g. Pseudo-second-order was the well-suited kinetics, where Langmuir isotherm could explain better for equilibrium adsorption data. Thermodynamic study shows MO adsorption is favourable, exothermic, and spontaneous. Finally, this study indicates that MOSWC could be a potential candidate for the adsorption of MO from wastewater.

The application of Rumex abyssinicus based activated carbon for Brilliant Blue Reactive dye adsorption from aqueous solution

The environmental pollution and human health impacts associated with the discharge of massive dye-containing effluents necessitate a search for cost-effective treatment technology. Therefore, this research work is conducted with the objective of investigating the potential of Rumex abyssinicus-derived activated carbon (RAAC) for the adsorption of Brilliant Blue Reactive (BBR) dye from aqueous solutions. Chemical activation with H₃PO₄ followed by pyrolysis was used to prepare the adsorbent. Characterization of the developed adsorbent was done using proximate analysis, pH point of zero charge (pHpzc), scanning electron microscope (SEM), Fourier transform infrared spectrometer (FTIR), Brunauer, Emmett, and Teller (BET), and X-ray diffraction (XRD). The experimental design and the effect of independent variables including pH (2, 6, and 10), initial dye concentration (50, 100, and 150 mg/L), adsorbent dosage (0.05, 0.1, and 0.15 g/100 mL), and contact time (20, 50, and 80 min) were optimized using the response surface methodology (RSM) coupled with Box Behnken design (BBD). The analysis results revealed the exitance of high specific surface area of 524 m²/g, morphological cracks, and the presence of multiple functional groups like -OH, C=C, alkene, and amorphous structure. Maximum removal efficiency of 99.98% was attained at optimum working conditions of pH 2, contact time of 50 min, dye concentration of 100 mg/L, and adsorbent dosage of 0.15 mg/100 mL, reducing the pollutant concentration from 100 to 0.02 mg/L. Evaluation of the experimental data was done using Langmuir, Freundlich, Temkin, and Sips isotherm models, in which the Langmuir model was found to be the best fit with the experimental data at R² 0.986. This shows that the adsorbent surface is homogeneous and mono-layered. Furthermore, the kinetic study confirmed that the pseudo second-order model best describes the experimental data with R² = 0.999. In general, the research work showed that the low cost, environmental friendliness and high adsorption capabilities of the activated carbon derived from Rumex abyssinicus could be taken as an effective nt for the removal of BBR dye from aqueous solutions.

Potential use of dry powder of Vossia cuspidata (Roxb.) Griff. rhizomes and leaves in methylene blue dye remediation

Phytoremediation is a promising, cost-effective, and eco-friendly process for wastewater treatment. Herein, the dry biomasses of Vossia cuspidata (Roxb.) Griff. leaves (PL) and rhizomes including aerial stems (PR) were used to effectively remediate methylene blue (MB) dyes. Interestingly, the adsorption uptake and removal efficiency of MB by PR were higher than those of PL; exceeding 97 and 91% in 35 and 25 min for 0.1 and 0.4 g/L MB, respectively. The MB diffusion within the PL and PR was insignificant and the adsorption kinetics was principally controlled by the surface MB-adsorbent interaction, as consistently approved by the pseudo-second order kinetic model. In addition, the adsorption increased rapidly with the plant dosage with high dependence on the initial MB concentration. Moreover, the impact of shaking speed on the adsorption was minor but temperature played a critical role where the highest efficiencies were recorded at 30 and 40 °C on PL (91.9%) and PR (93.3%), respectively. The best removal efficiencies were attained with PR at pH 6, but with PL at pH 8. The Temkin isotherm could perfectly simulate the experimental data (R2 > 0.97); suggesting a linear decrease of the adsorption heat of MB with the plant coverage.

Synthesis of hybrid framework of tenorite and octahedrally coordinated aluminosilicate for the robust adsorption of cationic and anionic dyes

Adsorption is an important process for the industrial dye effluent treatment. Many adsorbents are employed such as activated carbon, metal oxide, molecular sieves etc. All those adsorbents are having their own setbacks like longer adsorption time and lower adsorption capacity. So development of fast adsorption and higher adsorption capacity is very much essential. In this view, we synthesized hybrid crystal system of tenorite and aluminosilicate framework (CuO@AS) for the faster adsorption. It is characterized by FT-IR, HRTEM and WAXRD. WAXRD proved the hybridization of two crystal systems viz tenorite & alumina in monoclinic phase and silica in trigonal phase. The crystal structure drawn based on the WAXRD data. It is observed that the tenorite and aluminosilicate framework are separate, but they are interlinked through Cu-O-Al and Cu-O-Si bond. This interconnection makes the aluminium in six coordination and Cu in four coordination. Aluminium and copper has 3 and 2 Brønsted acid sites respectively. Moreover, copper has three more OH group, so totally 5 H⁺ and 3 OH^- sites in copper and aluminium are responsible for the faster adsorption with high adsorption capacity compared to reported literature. To test the adsorption tendency, Victoria Blue (VB) and Metanil Yellow (MY) dyes are employed at room temperature. The rate constant of Pseudo-second order kinetics for the VB and MY are 0.002462 g mg^-1 min^-1 and 0.001619 g mg^-1 min^-1 which indicated faster adsorption of VB than MY. Moreover, total adsorption capacity for VB (636 mg/g) is higher than MY (52 mg/g). This is due to the hybridization of tenorite and aluminosilicate. Thermodynamic data such as ΔG°, ΔH° and ΔS° revealed that the adsorption is spontaneous, chemisorption and highly disordered in the adsorbent-adsorbate interface. This disorderness is due to the disordered pores present in the material.

Recent advances in the removal of dyes from wastewater using low-cost adsorbents

The presence of hazardous dyes in wastewater cause disastrous effects on living organisms and the environment. The conventional technologies for the remediation of dyes from water have several bottlenecks such as high cost and complex operation. This review aims to present a comprehensive outlook of various bio-sorbents that are identified and successfully employed for the removal of dyes from aqueous environments. The effect of physicochemical characteristics of adsorbents such as surface functional groups, pore size distribution and surface areas are critically evaluated. The adsorption potential at different experimental conditions of diverse bio-sorbents has been also explored and the influence of certain key parameters like solution pH, temperature, concentration of dyes, dosage of bio-sorbent and agitation speed is carefully evaluated. The mechanism of dyes adsorption, regeneration potential of the employed bio-sorbents and their comparison with other commercial adsorbents are discussed. The cost comparison of different adsorbents and key technological challenges are highlighted followed by the recommendations for future research.

Woody residues of the grape production chain as an alternative precursor of high porous activated carbon with remarkable performance for naproxen uptake from water

Activated carbon prepared from grape branches was used as a remarkable adsorbent to uptake naproxen and treat a synthetic mixture from aqueous solutions. The material presented a highly porous texture, a surface area of 938 m² g^-1, and certain functional groups, which were key factors to uptake naproxen from effluents. The maximum adsorption capacity predicted by the Langmuir model for naproxen was 176 mg g^-1. The thermodynamic study revealed that the adsorption process was endothermic and spontaneous. The linear driving force (LDF) model presented a good statistical adjustment to the experimental decay data. A suitable interaction pathway of naproxen adsorption onto activated carbon was proposed. The adsorbent material was highly efficient to treat a synthetic mixture containing several drugs and salts, reaching 95.63% removal. Last, it was found that the adsorbent can be regenerated up to 7 times using an HCl solution. Overall, the results proved that the activated carbon derived from grape branches could be an effective and sustainable adsorbent to treat wastewaters containing drugs.

Recent Developments in the Application of Bio-Waste-Derived Adsorbents for the Removal of Methylene Blue from Wastewater: A Review

Over the last few years, various industries have released wastewater containing high concentrations of dyes straight into the ecological system, which has become a major environmental problem (i.e., soil, groundwater, surface water pollution, etc.). The rapid growth of textile industries has created an alarming situation in which further deterioration to the environment has been caused due to substances being left in treated wastewater, including dyes. The application of activated carbon has recently been demonstrated to be a highly efficient technology in terms of removing methylene blue (MB) from wastewater. Agricultural waste, as well as animal-based and wood products, are excellent sources of bio-waste for MB remediation since they are extremely efficient, have high sorption capacities, and are renewable sources. Despite the fact that commercial activated carbon is a favored adsorbent for dye elimination, its extensive application is restricted because of its comparatively high cost, which has prompted researchers to investigate alternative sources of adsorbents that are non-conventional and more economical. The goal of this review article was to critically evaluate the accessible information on the characteristics of bio-waste-derived adsorbents for MB’s removal, as well as related parameters influencing the performance of this process. The review also highlighted the processing methods developed in previous studies. Regeneration processes, economic challenges, and the valorization of post-sorption materials were also discussed. This review is beneficial in terms of understanding recent advances in the status of biowaste-derived adsorbents, highlighting the accelerating need for the development of low-cost adsorbents and functioning as a precursor for large-scale system optimization.

A review on three-dimensional cellulose-based aerogels for the removal of heavy metals from water

Contamination of the aquatic ecosystem by heavy metals is a growing concern that has yet to be addressed with an efficient, cost-effective and environmentally-friendly solution. Heavy metals occur naturally in the earth's crust and also result from anthropogenic activities. Due to the rapid increase in industrialization, there is an increase in consumer demands across various industries such as metal processing, mining sector, agricultural activities, etc. and this has led to an increase in heavy metal concentrations in the aqueous environment. Cellulose-based aerogels are a novel third-generation of aerogels that have recently attracted a lot of attention due to their high adsorption efficiency, eco-friendly prospects and cost effectiveness. In this review, recent literature on cellulose-based aerogel adsorbents used for the removal of heavy metals from aqueous solution has been compiled. The preparation of cellulose-based aerogels, adsorption mechanisms, effects of experimental factors such as pH, temperature, contact time, initial metal concentration and adsorbent dose have been discussed. In addition, cost analysis of cellulose-based adsorbents and some challenges in this research field along with recommendations of improvements have been presented. It can be concluded that functionalizing of cellulose-based aerogels with amine groups, thiol groups, other compounds such as nanobentonite and chitosan results in very high adsorption capacities. The adsorption studies revealed that pseudo-second-order kinetic model was the most commonly encountered adsorption kinetic model, and the most commonly encountered adsorption isotherm model was the Langmuir isotherm model. The main adsorption mechanisms were electrostatic interaction, complexation and ion exchange.

Sustainable approaches for removing Rhodamine B dye using agricultural waste adsorbents: A review

Rhodamine B (RhB) is among the toxic dyes due to the carcinogenic, neurotoxic effects and ability to cause several diseases for humans. The adsorption with agricultural waste adsorbent recorded high performance for the RhB removal. The current review aimed to explore the efficiency of different adsorbents which have been used in the few last years for removing RhB dye from wastewater. The data of adsorption of RhB using agricultural wastes were collected from the Scopus database in the period between 2015 and 2021. The use of agricultural wastes and adsorbents as a replacement for the activated has received high attention among researchers. The RhB removal methods by microbial enzymes and biomass occurred between 76 and 90.1%. In comparison, the adsorption with agricultural wastes such as activated carbon white sugar reached 98% within 12 min. The adsorption process has a wide range of pH (3-10) due to the zwitterionic forms of RhB. Gmelina aborea leaf activated carbon is among the agriculture wastes absorbents that exhibited 1000 mg g^-1 of the adsorption capacity. It appeared that the agricultural wastes adsorbents have a high potential for removing RhB from the wastewater.

Chitosan-Terephthalic Acid-Magnetic Composite Beads for Effective Removal of the Acid Blue Dye from Aqueous Solutions: Kinetics, Isotherm, and Statistical Modeling

A terephthalic acid-modified chitosan-magnetic nanocomposite (Cs-Tp@Fe₃O₄) was synthesized and characterized. The synthesized Cs-Tp@Fe₃O₄ was used in a batch process for the adsorptive removal of the acid blue 25 (AB-25) dye in aqueous solutions. The kinetic data were subjected to the pseudo-first-order, pseudo-second-order, Elovich, and intra-particle diffusion models, while the equilibrium data were evaluated with the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The effects of the initial dye concentration, contact time, and adsorbent dosage, as well as their interactions, on the removal efficiency were investigated using the design of experiments based on a central composite design, and the resultant data were modeled with the response surface methodology (RSM), artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), and multiple linear regression (MLR) approaches. The adsorption process followed pseudo-first-order with good agreement between the experimental Q _e(exp) and calculated Q _e(cal.) amounts of dye adsorbed, as well as the values of correlation coefficient, R ² (0.999) and percentage of sum square error, % SSE (0.640). All the investigated adsorption isotherms fitted all models well in the order of Dubinin-Radushkevich > Langmuir > Freundlich > Temkin with R ² > 0.9 with the monolayer maximum adsorption capacity of 440.24 mg/g obtained from the Langmuir isotherm. The RSM model predicted the maximum removal efficiency at an optimum initial dye concentration of 19.11 mg/L, a contact time of 95.3 min, and an adsorbent dosage of 0.18 g. Statistically, the models were fitted in the order of RSM > ANN > ANFIS > MLR. These results indicated that the prepared Cs-Tp@Fe₃O₄ is an efficient adsorbent for the AB-25 dye removal with excellent stability for water treatment applications.

Trapping Rhodamine B dye using functionalized mango (Mangifera indica) pod

The use of acid-modified mango pod (AMMP) sorbent for removing Rhodamine B (Rh-B) dye from aqueous media was investigated. Raw mango pod (RMP) and AMMP sorbents were characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), powdered X-ray diffractogram (PXRD), Fourier transform infrared (FTIR), point of zero charge pH (pH_pzc ), and Boehm titration (BT) techniques. Batch adsorption was employed to examine the influence of operational factors. Sorption kinetic parameters were calculated using pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models. The pseudo-second-order model best fitted the adsorption kinetic data most with maximum correlation coefficient (R²  > 0.99). The process of the adsorption was controlled by both boundary layer and intraparticle diffusion mechanisms. Four isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin) were utilized to analyze the equilibrium data at various temperatures. Freundlich model gave the best fit with the maximum regression (0.99), while the Langmuir isotherm model established a maximum monolayer adsorption capacity of 500 mg g^-1 . Thermodynamic parameters studied revealed that the interaction is spontaneous and endothermic in nature. The cost analysis of the current study provides convincing proof that AMMP is efficient for removing Rh-B dye from solution by providing a saving of 225.2 USD/kg, which is eight times cheaper than commercial activated carbon. Consequently, the study revealed that AMMP is a viable, effective, and sustainable sorbent for Rhodamine B dye removal. PRACTITIONER POINTS: The powdered X-ray diffractogram (PXRD) showed the formation of new and intense peaks with the presence of highly organized crystalline structures on acid-modified mango pod (AMMP). Surface morphology of AMMP showed well-developed open surface pores required for effective adsorption of Rh B dye molecules. Economic feasibility of the present study showed that AMMP is more affordable than commercial activated carbon that costs USD 259.5/kg, thus translated to a saving cost of USD 225.2/kg and more than 7.5 times cheaper than the commercial activated carbon (CAC).

Rhodamine B dye sequestration using Gmelina aborea leaf powder

Chemically prepared activated carbon derived from Gmelina aborea leaves (GALAC) were used as adsorbent for the removal of Rhodamine B (Rh-B) dye from aqueous solutions. The adsorptive characteristics of activated carbon (AC) prepared from Gmelina aborea leaves (GAL) were studied using SEM, FTIR, pH point of zero charge (pHpzc) and Boehm Titration (BT) techniques respectively. The effects of pH, contact time, initial dye concentration and solution temperature were also examined. Experimental data were analyzed using four different isotherm models: Langmuir, Freundlich, Temkin and Dubinin-Radushkevich. Four adsorption kinetic models: Pseudo-first-order (PFO), Pseudo-second-order (PSO), Elovich and Intraparticle diffusion models to establish the kinetics of adsorption process. The RhB dye adsorption on GALAC was best described by Langmuir isotherm model with maximum monolayer coverage of 1000 mg g-1 and R2 value of 0. 9999. The EDX analysis revealed that GALAC contained 82.81% by weight and 91.2% by atom of carbon contents which are requisites for high adsorption capacity. Adsorption kinetic data best fitted the PSO kinetic model. Thermodynamic parameters obtained for GALAC are (ΔGo ranged from -22.71 to -18.19 kJmol-1; ΔHo: 1.51 kJmol-1; and ΔSo: 0.39 kJmol-1 K-1respectively) indicating that the RhB dye removal from aqueous solutions by GALAC was spontaneous and endothermic in nature. The cost analysis established that GALAC is approximately eleven times cheaper than CAC thereby providing a saving of 351.41USD/kg. Chemically treated GAL was found to be an effective absorbent for the removal of RhB dye from aqueous solution.