Dye Solution pH Research Articles

Development and optimization of geopolymer adsorbent for water treatment: Application of mixture design approach

The current paper refers to the study of a new approach to optimizing the adsorptive properties of geopolymers by varying the aluminosilicate precursors from kaolin (K), metakaolin (MK), and coal fly ash (CFA) as internal synthesis factors. The simplex-augmented-centroid mixture design was applied to identify the optimal formulation from the three aluminosilicate precursors to develop a geopolymer (GP) with a distinctive structure that positively affects its dye adsorption efficiency. The variously formulated GP samples were tested for the removal of both methylene blue (MB-dye) and crystal violet dye (CV-dye) from an aqueous solution. The mathematical-statistical analysis of the experimental readings suggested that the generated special cubic models were significant, and thus the chosen approach was adequate for determining the optimum blending proportion. The optimization tools indicated that the optimal mixture from the three aluminosilicate precursors for developing a GP with high adsorption efficiency was 58% MK, 42% K, and 0% CFA. The optimized geopolymer (GPO) was synthesized and then analyzed using a variety of physicochemical techniques, which revealed the presence of an amorphous N-A-S-H gel-rich porous structure as an influencing property on the geopolymer's organic dye adsorption efficiency. The dependence of the adsorption mechanism of both MB-dye and CV-dye by GPO on the adsorbent dosage, contact time, initial dye concentration, temperature, and solution pH was evaluated. The isothermic and kinetic experimental readings for MB and CV-dyes adsorption by GPO were well fitted to the pseudo-second-order and Freundlich models, with an exothermic, favorable, and spontaneous adsorption reaction thermodynamically. The experimental studies in the lab scale on GPO produce comparable results. From these results, it has been concluded that the accuracy and feasibility of the mixture design simulation succeeded in optimizing and developing a geopolymeric sorbent material with great potential as an excellent economical agent for removing cationic dyes from aqueous media. This point represents an added value compared to traditional non-optimized geopolymer absorbents. Besides, this geopolymer material represents a significant application possibility for water treatment and remediation of hazardous dye pollutants.

Hydrothermal synthesis of cobalt substitute zinc-ferrite (Co1-xZnxFe2O4) nanodot, functionalised by polyaniline with enhanced photocatalytic activity under visible light irradiation

Fabrication and development of effective visible-light-responsive photocatalysts are required to tackle critical environmental issues. The aim of this study was to develop a nanocomposite material with improved photocatalytic activity for the degradation of industrial dyes such as Reactive Orange-16 (RO-16), Reactive Blue (RB-222), Reactive Yellow-145 (RY-145), and Disperse Red-1 (DR-1) without the need for a post-separation process after use. Here we report the hydrothermal synthesis of nanodots of Co1-xZnxFe2O4 (x = 0.3, 0.5 and 0.7), coated with polyaniline, by in situ polymerization. The Co1-xZnxFe2O4 nanodots, coated with polyaniline (PANI) nanograins, facilitated optical properties by easily capturing visible light. X-ray Diffraction (XRD) patterns and Scanning Electron Microscopy (SEM) images have confirmed the single-phase spinel structure of Co1-xZnxFe2O4 nanodot and nano-pore size of the Co1-xZnxFe2O4/PANI nanophotocatalyst. The specific surface area of the Brunauer–Emmett–Teller (BET) of the Co1-xZnxFe2O4/PANI photocatalyst was determined to be 24.50 m2/g by multipoint analysis. The final Co1-xZnxFe2O4/PANI (x = 0.5) nanophotocatalyst showed high efficiency in the catalytic degradation of toxic dyes (∼98% within 5 min), with good mechanical stability and recyclability under visible light irradiation. The nanophotocatalyst was re-used and its efficiency was largely maintained, even after seven cycles (∼82%) of degradation. The effects of various parameters, such as initial dye concentration, nanophotocatalyst concentration, initial pH of dye solution, and reaction kinetics were studied. According to the Pseudo-first-order kinetic model, photodegradation data followed the first-order reaction rate (R2 > 0.95) of degradation of dyes. In conclusion, a simple and low-cost synthesis process, speedy degradation and excellent stability of polyaniline-coated Co1-xZnxFe2O4 nanophotocatalyst could be used as a promising photocatalyst for dye-wastewater treatment.

Removal of Congo Red from Wastewater Using ZnO/MgO Nanocomposites as Adsorbents: Equilibrium Isotherm Analyses, Kinetics and Thermodynamic Studies

One step polyacrylamide gel method was used to synthesize the ZnO/MgO adsorbents and the adsorption behavior with Congo red (CR) from wastewater was extensively investigated. Various advanced techniques were applied to confirm the ZnO/MgO adsorbents consist of Zn, C, Mg and O elements and do not contain any other impurity elements. With the increase of MgO content, the morphology of ZnO/MgO adsorbent changes from the agglomeration of large particles to evenly dispersed fine particles and then to icicle structure. Results demonstrated that the adsorption process of ZnO/MgO adsorbents was significantly affected by the change in initial dye solution pH, initial adsorbent dosage, contact time and reaction temperature. The optimum pH, adsorbent dosage, contact time and reaction temperature is 9.81, 2 g /L, 65 min and 293 K, respectively. The maximum adsorption capacity of ZnO/MgO (nZnO:nMgO = 8:2) adsorbents (295.138 mg/g) for the adsorption of CR dye was approximately double that of previous reports (125 mg/g). The adsorption equilibrium data are well fitted by the Freundlich and Langmuir isotherm models. Thermodynamic studies indicate that the adsorption process of ZnO/MgO adsorbents is an exothermic process. Based on the experimental and theoretical analysis, the adsorption mechanism for the ZnO/MgO adsorbents consisted of hydrogen bonding, n-π interaction and electrostatic interaction. The present work pioneers the potential application of ZnO/MgO adsorbents for the adsorption of CR dye and further provides experimental evidence for the synthesis of other adsorbents.

Converting synthetic azo dye and real textile wastewater into clean energy by using synthesized CuO/C as photocathode in dual-photoelectrode photocatalytic fuel cell.

Cathode in photocatalytic fuel cell (PFC) plays a crucial role in degradation of organic contaminants. In this study, synthesized copper oxide (CuO) was loaded on carbon plate and used as photocathode in PFC for degradation of synthetic azo dye Reactive Black 5 (RB5) and real textile wastewater. Morphology and structural phase of the synthesized CuO were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Several operating parameters had been investigated such as light irradiation, initial dye concentration, and pH of azo dye solution within 6h of irradiation time. The lowest initial concentration of RB5 (10mg L-1) achieved 100% color removal compared to the highest initial concentration (40mg L-1) which only achieved 77.1% color removal within 6h of irradiation time. The influence of external resistance was significant in electricity generation but trivial in dye degradation efficiency. The external resistance of 6000 Ω yielded highest maximum power density, with Pmax of 0.2631μWcm-2, followed by 1000 Ω (0.2196μWcm-2) and 8000 Ω (0.1587μWcm-2), respectively. The real textile wastewater with dilution ratio (DR) 1:6 yielded the highest energy conversion efficiency, η (3.62%), followed by DR 1:4 (3.19%) and DR 1:2 (1.96%), respectively.

Kinetic and isotherm studies of Acid Orange 7 dye absorption using sulphonated mandarin biochar treated with TETA

This study contributes to the current state of knowledge by highlighting the physical–chemical interactions between biochar and dyes. The removal of Acid Orange 7 (AO7) dye by a modified biochar obtained from the wastes of mandarin peels (MPs) has been investigated in this work. A dehydration procedure with 80% H2SO4 under reflux was applied to produce an innovative biochar from MPs and then boiled with H2O2 and followed by boiling with triethylenetetramine to make mandarin biochar-C-TETA (MBCT). FTIR, SEM, EDX, BJH, BET, TGA, and DTA analyses were applied to investigate the MBCT. FTIR analysis showed an additional peak that confirmed the addition of the NH2 group to the MBCT structure. An amorphous carbon structure was also confirmed by XRD analysis. The AO7 dye solution pH was proved to give the best absorption at pH 2.0. Significant removal of AO7 dye 99.07% using an initial concentration of 100 mg/L of AO7 dye and a 0.75 g/L MBCT. The Langmuir (LNR) and Freundlich (FRH) isotherm models investigated the experimental results. The LNR was best suited to handle the working MBCT data. The maximum adsorption capacity (Qm) calculated for the MBCT was 312.5 mg/g using 0.25 g/L of the MBCT. Kinetic studies were conducted using the intraparticle diffusion (IND), film diffusion (FD), pseudo-first-order (PFOR), and pseudo-second-order (PSOR) models. The absorption rate was calculated using the ultimate value of the linear regression coefficient (R2 > 0.99), and the PSOR rate model was found to ideally describe the absorption process. The point of zero charge (pHPZC) was found to be 10.17. The electrostatic attractive-forces between the sorbent surface positively charged sites and negatively charged anionic dye molecules were the primary mechanism of the MBCT sorption of the AO7 dye’s anion absorption. The results indicate that the manufactured MBCT adsorbent may be useful for removing the AO7 dye from wastewater. MBCT can be used repeatedly for up to six cycles without dropping its absorption efficiency.

Study on MoS2/Fe‐MIL‐88NH2 Transition metal dichalcogenide/Metal‐organic framework as a novel composite for highly adsorption of methylene blue dye from aqueous solutions

The present study proposes a unique MoS2/Fe‐MIL‐88NH2 composite as an adsorbent for methylene blue (MB) from aqueous solutions for the first time. Different physicochemical techniques are utilized to characterize (metal–organic framework [MOF]/transition metal dichalcogenide [TMD]), including elemental analysis, Fourier transform infrared (FT‐IR), field emission scanning electron microscopy (FE‐SEM), zeta potential (ζ) measurement, and Brunauer–Emmett–Teller (BET) theory. The effects of different process factors on MB dye adsorption by composite are examined, including initial dye concentration, adsorbent loading, solution pH, temperature, and dye mixture. Various process parameters encompassing the initial dye concentration, adsorbent loading, solution pH, temperature, and mixture of dyes are investigated, and the equilibrium adsorption capacity towards MB is found up to 370 mg g−1 (when pH = 4.0, contact time is 90 min, and the adsorbent dose is 0.0068 mmol g−1). Experimental results reveal that the adsorption process is highly dependent on adsorbent dosage, initial MB concentration, and aqueous solution temperature. Equilibrium data are fitted onto Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models expressing the MB adsorption phenomena. Moreover, the isotherm data fit Freundlich mathematical models with maximum dye adsorption of 370 mg g−1. Sorption kinetics follows a pseudo‐second‐order model.

High Performance Carbon Material Prepared from Phalsa Using Mild Pyrolytic Process towards Photodegradation of Methylene Blue under the Irradiation of UV Light

In this study, we have used a mild pyrolytic process for the synthesis of luminescent carbon material from phalsa (Grewia asiatica Linn) and utilized it for the photodegradation of methylene blue (MB) in aqueous solution under the irradiation of ultraviolet (UV) light. The carbon material was found to be graphitic in nature and with carbon dot-like properties as demonstrated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS), and UV-visible techniques. The prepared carbon material was further studied for the elucidation of functional groups through Fourier transform infra-red (FTIR) spectroscopy. The carbon material exhibits the nanostructured phase which makes it a high surface area material for useful surface reactions. Different photodegradation aspects were investigated, such as initial dye concentration, catalyst dose, effect of pH of dye solution, reusability, electrochemical active surface area (ECSA), and charge transfer and scavenger. Optimum conditions of 15 mg carbon material, initial dye concentration of 2.3 × 10−5 M solution, and pH 5 of dye solution gave the highest outperformance degradation efficiency. The degradation mechanism of MB in aqueous solution was dominated by the hydroxyl radicals as verified by the scavenger study. The reaction kinetics of MB degradation was followed by the pseudo first order kinetics and highest values of rate constants in the low initial dye concentration and the acidic pH of the MB solution. Significantly, the carbon material prepared from phalsa was found to be highly stable, as proven by the reusability experiments. Furthermore, the high ECSA and low charge transfer resistance of carbon material enabled it to have better performance. The use of mild pyrolytic process for the preparation of high performance luminescent carbon material from the biomass could be a great roadmap for the synthesis of a new generation of carbon materials for a wide range of applications including bio-imaging, catalysis, energy conversion and environmental applications.

Photocatalytic activities of SnS thin films deposited at room temperature

Tin monosulfide (SnS) thin films were deposited on glass substrates at room temperature utilising a simple, inexpensive, and modified chemical approach known as Successive Layer Adsorption and Reaction (SLAR). The properties of the films were thoroughly studied using an XRD, SEM, EDAX, and UV-VIS spectrophotometer. It was possible to deposite smooth, homogeneous, and uniform thin films with pollycrystalline nature, orthorombic structure, and UV-VIS absorption. Under visible light irradiation, SnS thin films demonstrated high photocatalytic degradation of Methylene Blue. It showed effective degradation of a common textile dye available in the marker as well. Dye degradation was found to be of first order, following the Langmuir-Hinshelwood mechanism. Theoretical band structure calculations suggested that the relative positions of the highest valence band and lowest conduction band were 1.605 eV and -0.085 eV, respectively. The photocatalyst's reusability, the involvement of the hydroxyl radical in photodegradation, and the variation in photocatalytic performance of SnS thin films with dye solution pH and initial dye concentration were all examined. Changes in the cationic precursor's molarity caused changes in the thin film's crystallinity, stoichiometry, and bandgap. Non-stoichiometric films demonstrated higher photocatalytic activity.

Mg/Li Co-doped g-C3N4: An excellent photocatalyst for wastewater remediation and hydrogen production applications towards sustainable development

This study reports the one step synthesis of novel Mg/Li co-doped g-C3N4 (GCNML). It exhibited superior photoactivity in comparison to its mono-metallic counterparts and pristine g-C3N4 (GCNP). Synergistic effect of Mg and Li in GCNML can enhance rate of photocatalytic degradation of methylene blue dye to 0.04411 min−1 which is 5.4 times in contrast to GCNP. The pH of dye solution adjusted in alkaline range can further enhance its photocatalytic performance. The photo electrochemical studies show the high photocurrent density of 0.1258 mA/cm2 for GCNML which is 34 times to that of GCNP further supporting the synergetic effect of co-doping of Mg and Li. The improved photoactivity of photocatalyst is primarily attributed to better absorption ability of visible light, reduced optical band gap and retarded recombination rate of photo-induced h+- e− pairs and was not affected majorly by specific surface area of the respective materials. The antibacterial activity analysis further supports the potential application of prepared photocatalyst as a disinfectant agent against pathogenic bacterial strains (Escherichia Coli and Klebsiella pneumonia). Analysis in this study sustains the suitability of prepared photocatalyst as an efficient remediate of organic pollutants, water splitting, and bacterial disinfectant in wastewater.

The Adsorption Equilibrium and Kinetic Studies for The Removal of Crystal Violet Dye (Methyl Violet 6b) from Aqueous Solution Using Avocado Pear Seed Activated Carbon

In this study, adsorption equilibrium and kinetic studies for the removal of crystal violet (CV) from an aqueous solution were investigated using a batch adsorption process. The activated carbon was prepared by carbonizing the avocado pear seed at a carbonization temperature of 500OC for 1hr and was impregnated with a 30% concentration of aqueous HCl solution which was further activated in a muffle furnace at a temperature of 500OC for 1hr. The avocado pear seed activated Carbon obtained was characterized using proximate analysis, Fourier Transform Infra-Red Spectrophotometer (FT-IR) analysis and Scanning Electron Microscope (SEM) analysis. The effect of various adsorption parameters such as contact time (15-150 min), initial dye concentration (25-150 mg/L), adsorbent dosage (1-9 g), particle size and pH of dye solution were investigated. The adsorption equilibrium data were fitted into different isotherm models and the Langmuir model exhibited the best fit which implied that the adsorption of CV dyes onto avocado pear seed activated carbon was monolayer and the adsorbent surface was homogeneous and also; adsorption energy was uniform for all sites and there was no transmigration of adsorbate in the plane of the surface. The kinetic studies revealed that the adsorption data fitted well to the pseudo-second-order model with a high correlation coefficient of 0.977 when compared to other models, thus; signifying that the adsorption’s mechanism was chemisorption. APSAC shows a much better adsorption capacity for CV dye removal having a maximum adsorption capacity of 3.3254 mg/g and percentage removal of 99.995 %. Hence, APSAC can be used as an effective and low-cost adsorbent for the removal of CV dye from an aqueous solution.

Efficient Photodegradation of Methylene Blue using WLED with Nanosphere Graphitic Carbon Nitride Compared with its Bulk Counterpart

Herein, a simple solvothermal synthesis of graphitic carbon nitride nanosphere (g-CNN) at 180 ºC is reported. The photocatalytic activity of g-CNN was studied under an in-house developed white light emitting diode (WLED) reactor and characterized by FESEM, PXRD, FTIR, EDX, UV-visible spectroscopy and BET isotherm. The g-CNN has absorbance in visible light region and exhibits enhanced photocatalytic activity compared to bulk graphitic carbon nitride (BGCN) for photodegradation of methylene blue, which attributes to its lower surface area. The photocatalytic performance of g-CNN as function of pH of dye solution and catalyst amount were also studied. The g-CNN can be used for three repeated cycles with minimal change in photocatalytic efficiency. The solvothermal synthesis method at relative low temperature introduces terminal oxygen functionalities in g-CNN, which enhance light absorption and accelerate electron transfer results in improvement of photocatalytic efficiency of g-CNN. The results demonstrated the effectiveness of g-CNN as a photocatalyst for the treatment of water using visible light from WLED.

INFLUENCE OF OPERATING CONDITIONS ON THE ULTRAFILTRATION TREATMENT OF BRILLIANT BLUE BATIK DYE

The batik industry produces a large amount of wastewater that degrades water quality. Ultrafiltration (UF) is an efficient and low-pressure filtration method for water treatment, particularly for dye wastewater. This study aims to analyze the efficiency of commercial UF polyethersulfone (PES) membranes in the treatment of brilliant blue batik dye. The effect of operating conditions involving operating pressure (2, 3, 4 bar) and pH (3, 6, and 9) of dye solution at 50 mg/L on membrane performance was evaluated via a crossflow filtration system. Higher dye rejection was obtained at close to neutral pH and higher pressure. On the other hand, the fouling propensity was mainly affected by pressure and the membrane experienced a slower flux decline at lower pressure. This is owing to the synergistic interaction between size sieving and electrostatic repulsion. The optimum membrane performance was achieved at pH 6 and 3 bar. Future studies can work on real dye wastewater produced from the batik industry.

Green Synthesis of Fe3O4 Nanoparticles and Its Applications in Wastewater Treatment

In this paper, the extract of Citrus aurantium (CA) was used as a green approach for the preparation of Fe3O4 nanoparticles. The green Fe3O4 (Fe3O4/CA) was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy analysis (EDX), Fourier-transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) surface area measurement, and vibrating sample magnetometry (VSM). The synthesized Fe3O4/CA was used to remove methylene blue (MB) dye from an aqueous solution. A four-factor central composite design (CCD), combined with response surface modeling (RSM), was used to maximize the MB dye removal. The four independent variables, which were initial dye concentration (10–50 mg/L), solution pH (3–9), adsorbent dose (ranging from 200–1000 mg/L), and contact time (30–90 min), were used as inputs to the model of the perecentage dye removal. The results yielded by an analysis of variance (ANOVA) confirmed the high significance of the regression model. The predicted values of the MB dye removal were in agreement with the corresponding experimental values. Optimized conditions for the maximum MB dye removal (93.14%) by Fe3O4/CA were the initial dye concentration (10.02 mg/L), pH (8.98), adsorbent mass (997.99 mg/L), and contact time (43.71 min). The validity of the quadratic model was examined, and good agreement was found between the experimental and predicted values. Our findings demonstrated that green Fe3O4NPs is a good adsorbent for MB removal.

Preparation of metal organic framework materials with defects via a mixed-metallic centers strategy for enhanced removal of organic dye

Metal organic framework (MOF) materials display intriguing potential in wastewater treatment applications. In this study, a series of mixed MOF materials with several defects were designed and prepared via a strategy of mixed-metallic centers and the reaction process was lasted for only several hours at room temperature with water as environmental-friendly reaction medium. The MOF materials were characterized by Brunauer-Emmett-Teller (BET), Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), and were employed to enrich organic dyes from aqueous solution with methyl orange (MO) and methylene blue (MB) as model molecules. Several factors influencing adsorption efficiency such as contact time, initial concentration, pH of dye solution and ionic strength were systematically explored. Due to the difference of structure and charge of MO and MB, the adsorption behaviors of the materials for both model dyes were obviously different from each other. The results showed that the adsorption process could be better described by pseudo-second-order kinetics and Freundlich isotherm model. The adsorption capacity of mixed MOF material with the ratio of Co2+ and Ni2+ of 1:1 for MO was 380.91 mg/g, much higher than those of MOF materials with single metallic center (255.15 mg/g of the material with Co2+ and 176.65 mg/g of the material with Ni2+), indicating the advantages of the preparation strategy and defects of the mixed MOF material produced in the preparation process in the adsorption field. However, the adsorption capacities of the prepared MOF materials for MB were close to each other. Furthermore, it would be possible to achieve a highly selective adsorption of MO from the mixed aqueous solution of MO and MB through choosing the appropriate NaCl concentration. This study can provide a method of increasing the diversity and functionality of the MOF materials.

Waste-Coffee-Derived Activated Carbon as Efficient Adsorbent for Water Treatment.

Activated carbon prepared from waste coffee was utilized as a potential low-cost adsorbent to remove Rhodamine B from aqueous solution. A series of physical characterizations verify that the obtained activated carbon possesses a layered and ordered hexagonal structure with a wrinkled and rough surface. In addition, high specific surface area, appropriate pore distribution, and desired surface functional groups are revealed, which promote the adsorption properties. Various adsorption experiments were conducted to investigate the effect on the absorption capacity (e.g., of initial dye concentration, temperature and solution pH) of the material. The results showed that the waste-coffee-derived activated carbon with a large surface area of approximately 952.7 m2 g-1 showed a maximum uptake capacity of 83.4 mg g-1 at the pH of 7 with the initial dye concentration of 100 mg L-1 under 50°C. The higher adsorption capacity can be attributed to the strong electrostatic attraction between the negatively charged functional groups in activated carbon and the positively charged functional groups in RB. The kinetic data and the corresponding kinetic parameters were simulated to evaluate the mechanism of the adsorption process, which can fit well with the highest R2. The adsorption results confirmed the promising potential of the as-prepared waste-coffee-derived activated carbon as a dye adsorbent.

Augmenting the Photocatalytic Performance of Direct Z-Scheme Bi2O3/g-C3N4 Nanocomposite

Huge demands for photocatalytically efficient visible-light-induced catalysts have spurred widespread interest in building adaptable heterojunctions. Here, we used in situ thermal polymerization to synthesise the Z-scheme Bi2O3/g-C3N4 heterojunction. The optical, structural, chemical, compositional and photocatalytic behaviours of the samples were analysed through various analytical techniques and photocatalytic methylene blue (MB) dye degradation reaction. Among the various ratios of Bi2O3/g-C3N4 heterojunction composites, the 1:1 ratio showed improved visible-light-induced catalytic activity, which attained 91.2% degradation efficiency after 120 min of visible-light exposure. The dye degradation efficiency was calculated under various environmental conditions by varying the dye concentration, solution pH and catalyst dosage. A improved Z-scheme photocatalytic mechanism was proposed in light of the results. A potential mechanism was suggested to explain the photocatalytic activity, and trapping experiments supported it. Last but not least, this strategy might be helpful to prepare the heterojunction photocatalyst for the degradation of organic pigments.

Low power LED assisted effective photodegradation of cationic and anionic dyes by zinc phthalocyanine based 2D polyamide sensitized CuO photocatalyst

The present investigation details the synthesis and photocatalytic performance of an organic-inorganic hybrid system involving phthalocyanine-based 2D polyamide sensitized CuO photocatalyst in the presence of low-power LED visible light. Zinc phthalocyanine-based 2D polyamide (2D-ZnPcPA), CuO nanomaterial and their nanocomposites (2D-ZnPcPA@CuO) were successfully synthesized and characterized by Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) to understand the structure, size, morphology and optical properties. To examine the photodegradation capability of newly synthesized photocatalysts in the presence of the low-power white LED (16 W) as a source of visible light, cationic methylene blue (MB) and anionic congo red (CR) dyes were employed as modular pollutants. The impact of different parameters on photocatalytic activity such as photocatalyst dosage, contact time, pH of dye solution and photocatalyst re-usage, is examined. The results indicate that photosensitizing CuO with 2D-ZnPcPA improved photocatalytic performance for the photodegradation of MB and CR dyes substantially. The removal effectiveness of MB and CR under optimised conditions was determined to be greater than 96 and 93% in 90 minutes respectively.

Tea Waste Products: A New Low-Cost and Green Adsorbent Alternative for Rhodamine-B Dye Removal

Tea waste products were thrown out without any intention to utilize their potential benefits. This waste will help to improve industries to absorb rhodamine-B (RhB) dye pollutants currently used by various industries. This study evaluated the application of tea waste products to remove Rh-B from aqueous systems by investigating adsorption kinetics in a batch process. The ability and mechanism of Indonesian black and green tea in RhB adsorption were determined by optimizing temperature, pH, contact time, and concentration of dye solution. Achievement of equilibrium attained at 40 min for black tea (BT) and green tea (GT). Subsequently, the adsorption capacity reached optimum at 80 and 70 °C for GT, and the maximum adsorption capacities for BT and GT were 22 and 47 mg/g, respectively, at pH 2.5. The absorption of RhB in both bio-sorbents was an exothermic process that well fit the Langmuir model and a pseudo-second-order reaction. The presented R2 values from the Langmuir isotherm are 0.9967 (BT) and 0.9979 (GT). The separation factor was determined as 0.026 (BT) and 0.055 (GT). Thermodynamic studies were carried out to calculate free energy, enthalpy, and entropy changes. The result showed that the removal study of BT and GT is 59.06 and 60.25%, respectively, using 10% acetic acid. Study comparisons were carried out on both teas with other bio-sorbents for more improvement. These results show that tea waste products can be used as alternative adsorbents to absorb RhB from wastewater.

Remediation of different dyes from textile effluent using activated carbon synthesized from Buxus Wallichiana

In this project, eriochrome black T (EBT) and methylene blue (MB) which are well known textile and other industries effluents pollutants were removed by activated carbon prepared from the plant, having no medicinal or other importance (stem of Buxus Wallichiana) by pyrolysis method. Initially, different analytical techniques were applied to describe the composition and morphology of the prepared activated carbon (ACs). Different structural analysis found that pyrolysis at 600 °C brought a significant change in chemical composition of the prepared ACs. EDX elucidated high carbon contents ACs was formed which is highly desires for adsorption process. For optimization of different conditions for adsorption of both the dyes, different parameters which include initial concentration of both the dyes, pH of dye solutions, contact time and temperature were investigated in batch mode. It was found from adsorption of dyes on the prepared ACs that maximum amount of MB and EBT adsorption were 866.15 mg/g and 383 mg/g respectively. Also, adsorption of MB on the prepared ACs was higher than commercial ACs while in case of EBT commercial ACs has higher adsorption value than the prepared ACs. Due to physisorption nature, maximum adsorption of both the dyes took place at low temperature. The pH at PZC for ACs was around 5.9. The adsorptions of the EBT and MB on the prepared ACs were exothermic in nature due to the -ve value of enthalpy. The reusability of the prepared ACs was checked, with the adsorption capacity dropping from 126 mg/g to 103 mg/g over the course of five cycles in the real sample. These findings suggest that Buxus Wallichiana stem is a suitable biosorption substitute for the remediation of cationic (MB) and anionic (EBT) dyes from textile industrial effluents . • Activated carbon prepared from Buxus Wallichiana by pyrolysis method. • Efficient adsorbent for the removal of MB and EBT dyes. • Adsorption capacity for MB reached to 866.15 mg/g while 383 mg/g for EBT. • Highly stable and recyclable adsorbent up to five cycles.

Removal of sulfonated azo Reactive Red 195 textile dye from liquid phase using surface-modified lychee (Litchi chinensis) peels with quaternary ammonium groups: Adsorption performance, regeneration, and mechanism

In the present work, chemically modified lychee peels were synthesized using glycidyltrimethylammonium chloride (GTMAC) and used to remove Reactive Red 195 (RR 195) from an aquatic environment. Lychee peel powder (LPP), GTMAC-modified LPP (G-LPP), and RR-195/G-LPP were characterized by BET/BJH, FTIR, pHPZC, XRD, and FE-SEM/EDX analyses. Adsorption tests were performed in batch mode, and various operational variables like initial dye concentration (25–250 mg/L), G-LPP mass (10–80 mg/30 mL), stirring speed (0–400 rpm), solution pH (1.0–10.0), contact time (0–480 min), and temperature (298–328 K) were studied to optimize the process. The solution pH strongly affects RR 195 removal efficiency. The maximal dye removal was 94.5%, achieved at pH 4.0. The non-linear assessment of isotherm and kinetics showed that the sorption system was fitted well by the Langmuir model (R2 > 0.9899) and pseudo-first-order kinetic model (R2 > 0.9918). The Langmuir maximum monolayer sorption capacities, qmax, at temperatures of 298, 308, 318, and 328 K are 144.9, 137.7, 130.1, and 124.2 mg/g, respectively, thus suggesting favorable adsorption at low temperatures. The Ea (activation energy) was computed to be 16.3 kJ/mol, which indicated that the adsorption behavior was mainly attributed to physisorption. The thermodynamic variables ΔHo (−46.6 kJ/mol), ΔSo (−133 J/mol K), and ΔGo (−6.8693 ∼ −2.9777) revealed that the sorption process was exothermic, feasible, and spontaneous. The binding of RR 195 dye onto the G-LPP surface was through hydrogen bonding and electrostatic interactions. Desorption efficiency follows the order NaOH (91.2%) > NaCl (69.6%) > HCl (65.2%) > methanol (58.4%) > H2SO4 (48.1%) > acetone (45.5%) > ethanol (39.2%) > HNO3 (31.6%). After five consecutive cycles of regeneration and reusability of G-LPP adsorption performance, the adsorption efficiency was better than 77.3%. The results show that G-LPP is a promising adsorbent for removing RR 195 dye from an aqueous solution.