Biosorption Of Dye Research Articles

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.

Optimization of biosorption of industrial dyes into Luffa cylindrica functionalized with quaternary ammonium salts

Optimization of biosorption of industrial dyes into Luffa cylindrica functionalized with quaternary ammonium salts

Biosorption of dyes in wastewater using chitosan/polyethylene nanoparticle as adsorbent

Chitosan/low-density polyethylene (CHNP/LDPE) nanoparticles, sized at approximately 200 nm, were developed as effective adsorbents for removing dyes from wastewater. This study involved a systematic experimental investigation to evaluate the effects of several parameters: adsorbent dosage, contact time, temperature, pH, and initial dye concentration, all conducted in batch experiments at ambient temperature. The optimal adsorption conditions were identified; specifically, a pH of 5 was most effective for Methylene Blue (MB) dye, while a pH of 6 yielded the best results for Bromocresol Green (BG) dye. The highest removal efficiency was observed with an initial dye concentration of 50 mg/L and an adsorbent dosage of 0.05 mg/L. Equilibrium studies indicated that the adsorption process conformed to the Langmuir isotherm model for single systems. Notably, MB exhibited a higher adsorption capacity of 147 mg/g compared to BG’s capacity of 142.8 mg/g. These findings underscore the potential of CHNP/LDPE biocomposites as a novel biosorbent for dye removal in wastewater treatment applications, suggesting an efficient and environmentally friendly approach to managing dye pollutants.Graphical abstract

Eco-Friendly Green Approach to the Biosorption of Hazardous Dyes from Aqueous Solution on Ragweed (Ambrosia artemisiifolia) Biomass

The presented research includes the preparation, characterization, and implementation of magnetic biosorbent (Fe3O4/RWB), obtained from ragweed (Ambrosia artemisiifolia) biomass. Fe3O4/RWB was examined for the removal of a hazardous dye, malachite green (MG), from an aqueous solution in a batch system. The effects of the experimental parameters—initial dye concentration (10–300 mg/L), contact time (0–120 min), biosorbent dose (1–5 g/L), initial pH (2–10), ionic strength (0–1 mol/L), and temperature (298–318 K) on dye biosorption—were studied. The results showed that increases in biosorbent dose, contact time, and initial pH led to an increase in biosorption efficiency, while the increase in initial dye concentration, the ionic strength, and temperature had the opposite effect. The biosorption kinetics for MG on Fe3O4/RWB were analyzed with pseudo-first-order, pseudo-second-order, and Elovich kinetic models, while the Langmuir, Freundlich and Temkin isotherm models were used for equilibrium data analysis. It was observed that the MG biosorption followed the pseudo-second-order kinetic model, whereas the Langmuir model was the best fit for the equilibrium biosorption data of MG, with a Qmax of 34.1 mg/g. the desorption of MG from Fe3O4/RWB indicated reusability in five adsorption/desorption cycles, good performance, and potential in practical applications.

Novel Efficient and Eco‐Friendly Biosorbent Derived from Ditax (Detarium senegalense) Fruit Hulls for Removal of Cationic Dyes: Adsorption Modeling and Statistical Optimization

AbstractRemediation of wastewater laden with dyes using optimized and less expensive techniques remains a challenge for environmental protection. In the current research work, alkaline activation approach was employed to derive a biosorbent from ditax fruit hulls (DS‐FHB), and its sorption performance was tested on Methylene blue (MB) dye biosorption with optimizing adsorption parameters. Structural and chemical properties of DS‐FHB including crystallinity, morphology, and surface functionality were analysed using XRD, SEM, FTIR technics, and pHPZC determination. Optimization of adsorption parameters using a centered composite design (CCD) from response surface methodology led to achieving a peak dye removal rate of 98.97 %. The optimal conditions were determined as DS‐FHB mass of 0.23 g, pH 7.12, contact time 39.00 min, and initial MB concentration of 69.35 mg/L. The findings demonstrated a strong alignment with both the Langmuir isotherm and pseudo‐second order kinetic model, suggesting their appropriateness in describing the adsorption process of MB onto DS‐FHB. According to the Langmuir isotherm model, the sorption of MB dye onto DS‐FHB occurred by monolayer formation with a maximum dye sorption capacity of 96.453 mg/g. Based on the structural and physico‐chemical properties of DS‐FHB biosorbent, and its adsoption applicability evaluated in the experimental conditions, detax derived‐biosorbent can be proposed as a successful and effective low‐cost biosorbent for removing cationic dyestuffs from aqueous solutions.

Biosorption of Remazol Brilliant Blue R textile dye using Clostridium beijerinckii by biorefinery approach.

The current study proposes RBBR biosorption by Clostridium beijerinckii DSMZ 6422 biomass remaining after biobutanol production from pumpkin peel (PP) by a zero-waste approach. Efficient biobutanol production was achieved by investigating initial PP concentrations (5-20% without or with enzymatic hydrolysis) and fermentation time. According to this, the highest concentrations of biobutanol and total ABE were obtained as 4.87g/L and 8.13g/L in the presence of 10% PP without enzymatic hydrolysis at 96h. Furthermore, based on the zero-waste approach, C. beijerinckii DSMZ 6422 biomass obtained after biofuel production was used as a biosorbent for the removal of RBBR dye. Response surface methodology (RSM), commonly utilized for the experimental design, was used to specify the optimized biosorption conditions of RBBR, including initial dye concentration (50-200mg/L), initial pH (2-6), biosorbent concentration (1-3g/L), and contact time (0-240min). The highest biosorption under optimized conditions with RSM was 98% in the presence of 194.36mg/L RBBR and 2.65g/L biosorbent at pH 2 and 15min. This is the first report in the literature about the biosorption of RBBR dye by anaerobic C. beijerinckii biomass after the biobutanol production process. This study also shows the efficient usage of agricultural and microbial wastes in different areas based on zero-waste applications.

A novel biosorbent material from waste fish scales (Cyprinus carpio) for biosorption of toxic dyes in aquatic environments

AbstractPolluted water sources are a growing concern in our world today, with more and more of our precious freshwater sources becoming contaminated. Pollution can come from a variety of sources, such as industrial discharge, agricultural runoff, and even urban runoff. Several treatment technologies have been investigated, mainly for dye pollution from textile and industrial wastes. In this study, the biosorption of methylene blue dye from the water environment was examined utilizing a low-cost and biodegradable biomaterial. Waste fish scales modified with NaOH were used as biomaterial. The biosorption effect of methylene blue concentration and pH variables was optimized. SEM for the surface morphology of the biomaterial and FT-IR analyses for the detection of functional groups were performed. The characterization of methylene blue biosorption was conducted to fully understand its nature, including its kinetics, equilibrium, and thermodynamic works. It has been determined that the biosorption process conforms most closely to the pseudo-second-order kinetic model for its kinetic results and to the Langmuir isotherm for its equilibrium results. Based on the Langmuir isotherm data, the maximum capacity for biosorption (qmax) was found to be 344.82 mg g−1. The thermodynamic results showed that the process of biosorption of methylene blue on various surfaces is spontaneous and occurs via physisorption. Additionally, the experimental design method was utilized to determine the optimum conditions of the methylene blue biosorption process under various conditions. The maximum biosorption capacity was determined to be 102.367 mg g−1 at the optimal conditions. The potential of biosorbent derived from the waste fish scales is promising as a novel biosorbent material due to its unique surface morphology and high biosorption capacity.

Enhancing environmental sustainability: Butea monosperma leaves as a key component in WO3-based composites for water purification and therapeutic applications.

In this research, a novel nano-biocomposite material, namely, tungsten trioxide-Butea monosperma leaf powder (WO3@BLP), is an effective and eco-friendly adsorbent used for the mitigation of congo red (CR) and crystal violet (CV) dyes from its aqueous phase. The as-prepared WO3@BLP was characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), DLS analysis, and TGA. Many factors such as solution pH, WO3@BLP dose, temperature, contact time, and initial CR/CV dye concentrations were exploited to monitor the adsorption efficiency of WO3@BLP composites. The biosorption of both CR and CV dyes followed the Langmuir isotherm, with maximum adsorption capacities (qmax) reaching 84.91 mg g-1 for CR at pH 2.3 and 162.75 mg g-1 for CV at pH 8, fitting of kinetics data to the PSO model with closed values of qeexp (mg g-1) and qecal (mg g-1), i.e., 25.69 to 25.38 mg g-1 for CR dye and 29.06 to 29.08 mg g-1 for CV dye. The interaction mechanism behind the adsorption of CR and CV dyes onto the WO3@BLP bionanocomposite includes electrostatic interaction and surface complexation. The synthesized materials were tested for antifungal activity against three different Candida cells, i.e., C. albicans ATCC 90028, C. glabrata ATCC 90030, and C. tropicalis ATCC 750, by using broth dilution method on the minimum inhibiting concentration (MIC). Furthermore, the cytotoxicity of nano-formulated WO3@BLP was studied by in vitro hemolytic assay on a human host. Overall, this research presents a pioneering nano-biocomposite, WO3@BLP, as a sustainable adsorbent for CR and CV dye removal, adhering to Langmuir isotherm and pseudo-second-order kinetics. Its multifaceted approach includes elucidating interaction mechanisms, demonstrating antifungal activity, and assessing cytotoxicity, marking a significant advancement in environmental remediation.

Repurposing cottonseed meal as dye biosorbent

We successfully repurposed cottonseed meal (CSM) into alginate composite hydrogel beads for dye adsorption via a simple and efficient method. The beads entrapped CSM with up to 80 wt%. Effect of CSM on the physiochemical properties of composite hydrogel beads including swelling behaviors, chemical structures, thermal stability, and methylene blue (MB) adsorption capacity, was investigated. Compared to alginate gel beads, the alginate/CSM composite system exhibited a drastic increase in thermal stability and a synergistic effect in dye adsorption capacity, where the dye adsorption capacity was well maintained, despite the inherently lower capacity when used alone. Such synergistic effect appeared to be linked to the reduced size of CSM particles within the gel network, while dye adsorption mechanism was attributed to the electrostatic attraction and hydrogen bonding between the biosorbents and dye. Our current study offers a feasible and cost-effective approach for upcycling CSM as biosorbent for dye decontamination.

Biosorption of anionic and cationic azo dye onto red macro alga: Determination of the significant variables using resolution V fractional factorial design

Naturally inspired biosorbent from macro algae species are favored because of its excellent biosorptive capability and low cost. The present investigation reports the potential of red macro-alga, E. spinosum as a biosorbent to remove both anionic and cationic azo dyes, namely Acid Yellow 17 (AY17) and Methylene Blue (MB) from aqueous solution. A resolution V fractional factorial design (2v5-1) analysis was employed to study the main effects and interaction of variables on the biosorption process. Factorial matrix with five variables; pH (2–12), dosage (0.4–2 g/L), initial concentration (50–200 mg/L), contact time (5–120 min) and temperature (30-50 °C) at two levels were conducted in batch study. Pareto charts and ANOVA (within 95% confidence level) were applied to examine the relationship and significance between independent variables and their interactions. A regression model with R2AY17 = 0.9998 and R2MB = 0.9995 was implemented to fit the experimental data. The results obtained indicated that the most significant variables that affected biosorption process were initial concentration and the dosage of the dyes. Experimental screenings are crucial in optimization studies. The remarkable performance of E. spinosum as biosorbent to absorb both dyes shows a great potential to be implemented for local marine macro alga as an alternative. Resource for biosorption process.

Simultaneous biosorption of acid violet and reactive yellow dyes by Cladosporium cladosporioides

The synthetic dye mixture of Acid Violet 90 and Reactive Yellow 145 was treated with dead Cladosporium cladosporioides biomass. The individual concentrations were calculated with the first-order derivative spectrophotometric method. The calibration curves were plotted at wavelengths of 578.4 nm and 318.2 nm in the derivative spectrum for Acid Violet 90 and Reactive Yellow 145, respectively. The calculated limit of quantitation value is ~ 2.5 mg/L for Acid Violet 90 and ~ 1.5 mg/L for Reactive Yellow 145. The achieved mean recovery percentage values are around 100%. The highest removal efficiency (100%) was obtained for both dyes at pH 4 using 0.25 g biomass and 50 mg/L of each dye in 60 min reaction time with 150 rpm shaking speed. The hydrochloric acid solution was used for biomass regeneration, and the removal efficiencies remained at 99% and 89% for Acid Violet 90 and Reactive Yellow 145 in the third cycle.Graphical abstractBiosorption process

Green biosourced composite for efficient reactive dye decontamination: immobilized Gibberella fujikuroi on maize tassel biomatrix

Biosorptive treatment with microbial biomass is regarded as an environmentally friendly and effective way to reduce dye contamination in contaminated aquatic environments. Immobilizing microbial cells for use in this process can significantly improve their effectiveness as biosorbents in the water treatment process. The current investigation searches for a sustainable and environmentally friendly approach to decolorization by employing a green biocomposite material sorbent system (ZM@GFC) created by immobilizing fungal cells (Gibberella fujikuroi) on maize tassel tissues to efficiently remove Reactive Yellow 2 (RY2) from contaminated water sources. Batch and dynamic flow tests were performed to evaluate the biodecolorization properties of the newly created immobilized biomaterial as well as the effects of several essential operating conditions factors on the sorption behavior. Biosorption yields of 95.7% and 90.0% in batch and dynamic modes were achieved for experimental dye decolorization. The biosorption of RY2 by ZM@GFC occurred fast and achieved equilibrium within 60 min. The pseudo-second-order kinetic model elucidated the dye biosorption onto ZM@GFC. The Langmuir model provided a more accurate representation of the results than the Freundlich model. At the same time, Redlich-Peterson isotherm demonstrated the best level of agreement with the experimental data. These findings indicate that the biosorption mechanism predominantly involved the formation of a monolayer covering and that the energy properties of the ZM@GFC surface were uniform. The breakthrough capacity at the exhaustion time was 537.32 mg g−1. The predicted cost of generating ZM@GFC was anticipated to be 61.03 USD/kg. The investigations on safe disposal demonstrated that the biosorption process did not generate any secondary pollution. In conclusion, using maize tassel tissue as an immobilized decolorization agent offers a possible method for removing reactive azo dye pollutants from the aquatic medium that is both economical and environmentally benign.

Screening of azo dye biosorption efficacy of free, immobilized, indigenous bacterial strains associated with azo dye contaminated river water—An in vitro study

AbstractAzo dye degradation utilizing microorganisms has acquired significance over the last decades, owing to its beneficial properties such as rapid degradation, economic feasibility, and eco‐friendly. In this work, azo dyes (Methyl red and methylene blue) degradation efficacy using indigenous bacterial strains Pseudomonas sp. and Bacillus sp. as free and immobilized cells were investigated under in vitro batch decolorization setup was carried. Most importantly, the bacterial cells of both strains were immobilized with sodium alginate and the immobilized cells were evaluated for dye decolorization efficacy under laboratory conditions. An eco‐toxic assessment of the degraded products was done using in vitro phytotoxicity tests and in silico analyses. Among the free and immobilized cells, maximum decolorization efficacy was observed in the Pseudomonas sp. immobilized cells which exhibited 74.5% decolorization efficacy, and the maximum decolorization efficacy of free cells was 63% of was observed. Ecotoxicity of the dye‐degraded products was screened by determination of phytotoxicity. Seedlings emergence of groundnut seeds exposed to degraded dye products revealed phytotoxicity. Results indicated that degraded dye products of methyl red derived from Pseudomonas sp. showed 93.0% seedling emergence, and methylene blue‐degraded products Pseudomonas sp. degraded dye products supported 92.0% seedling emergence, respectively. Bacterial cells immobilized with biocompatible polymers can be effectively utilized in wastewater treatment without affecting the ecological components. The findings highlight the value of this work in contributing to the domain of sustainable and eco‐friendly wastewater treatment technology.

Bio-composite of chitosan and polyethylene for the biosorption of dye in wastewater

This study investigated the potential of a biocomposite adsorbent made of low-density polyethylene-chitosan nanoparticles (LDPE/CHNP) for removing Congo red and Crystal violet dyes from wastewater. Batch experiments were conducted at room temperature to study the effects of pH, contact time, initial concentration, adsorbent dosage, and temperature on the adsorption process. The results showed that the maximum sorption of Congo red and Crystal violet occurred at pH 8. The adsorption process was rapid in the first 30 minutes of contact, with more than 90% uptake, and equilibrium was achieved with 150 rpm agitation. The biosorption of Congo red and Crystal violet dyes was described using Langmuir, Freundlich, and isotherm models. The Langmuir model was found to fit the equilibrium data better, with a correlation coefficient of 0.99 and a maximal adsorption capacity of 27.1 mg/g. Based on these results, it can be concluded that the biocomposite adsorbent made of low density polyethylene-chitosan nanoparticles (LDPE/CHNP) has the potential to be an effective and abundant alternative biomass for removing these dyes from wastewater. The LDPE/CHNP biocomposite adsorbent could be applied as a remediation method for color contamination in wastewater.

Marine-derived fungus Paramarasmius palmivorus CBMAI 1062 applied to sulphur indigo blue decolorization, degradation and detoxification.

The use of marine microorganisms in the treatment of dyes and textile effluents is promising in view of their tolerance to salinity, a characteristic found in this kind of effluent. In this study, different culture conditions were applied to evaluate the decolorization, degradation, and detoxification of Sulphur Indigo Blue (SIB) by the marine-derived basidiomycete Paramarasmius palmivorus CBMAI 1062. Low salt concentration (SLS) and high salt concentration (SMASHS) media were used. P. palmivorus decolorized 100 % and 91.38 % of SIB after 120 h of growth in the SLS medium and after 168 h of growth in the SMASHS medium, respectively. Laccase activity was detected only in the SLS bioassay. UV-Vis, FT-IR, and GC-MS analyses indicated the occurrence of dye biosorption and biotransformation. In the SLS medium metabolites associated with SIB biotransformation (e.g. aldehyde, alkanes, and phenols) were detected. The toxicity measured by Cucumis sativus decreased from 45.41 % to 24.11 % in the SLS bioassay, while in SMASHS medium there was no change in toxicity. The efficiency for decolorization and detoxification of SIB indicates that microorganisms from the marine environment can be a source for biotechnological application in bioremediation processes carried out under saline conditions, adding value to blue biotechnology.

Biosorption of Toxic Reactive Blue Textile Dye from Effluent Water Using Immobilized Biomass Based Adsorbent

The present research employed immobilized Canna indica beads (CIBs) to obtain maximum degradation of highly toxic Reactive Blue Dye (RBD), predominantly used in textile industry. The CIBs were characterized using FTIR and SEM-EDX analysis. A batch adsorption study was conducted to measure the removal of harmful RBD dye. Different factors were examined in the biosorption technique to achieve the maximum level of toxic dye elimination, such as adsorbent-solute interaction time (5-120 min), solution pH (2-10), adsorbent dose (25 to 250 mg/100 mL), RBD concentration (50-250 mg/L), and temperature (30-60°C). Removal of 99.96% of RBD was successfully achieved at the optimum pH 7, RBD concentration of 50 mg/L, adsorbent dosage of 150 mg/100 mL, a temperature of 303 K, and 60 min of interaction time. The Langmuir isotherm and pseudo-second-order (PSO) kinetic model data have been found to be an ideal match compared to the Freundlich isotherm and pseudo-first-order (PFO) kinetic model. The maximum adsorption capacity onto CIBs biosorbent was found to be 70.49 mg/g. It was noticed that the chemical reaction occurred naturally and released heat during the process which denoted an exothermic reaction. These results shown that the adsorption of RBD removal is efficient using prepared adsorbent from Canna indica root tubers. Therefore, these CIBs could be used for other toxic dyes and heavy metals from industrial wastewater.

Biosorption of Toxic Reactive Blue Textile Dye from Effluent Water Using Immobilized Biomass Based Adsorbent

The present research employed immobilized Canna indica beads (CIBs) to obtain maximum degradation of highly toxic Reactive Blue Dye (RBD), predominantly used in textile industry. The CIBs were characterized using FTIR and SEM-EDX analysis. A batch adsorption study was conducted to measure the removal of harmful RBD dye. Different factors were examined in the biosorption technique to achieve the maximum level of toxic dye elimination, such as adsorbent-solute interaction time (5-120 min), solution pH (2-10), adsorbent dose (25 to 250 mg/100 mL), RBD concentration (50-250 mg/L), and temperature (30-60°C). Removal of 99.96% of RBD was successfully achieved at the optimum pH 7, RBD concentration of 50 mg/L, adsorbent dosage of 150 mg/100 mL, a temperature of 303 K, and 60 min of interaction time. The Langmuir isotherm and pseudo-second-order (PSO) kinetic model data have been found to be an ideal match compared to the Freundlich isotherm and pseudo-first-order (PFO) kinetic model. The maximum adsorption capacity onto CIBs biosorbent was found to be 70.49 mg/g. It was noticed that the chemical reaction occurred naturally and released heat during the process which denoted an exothermic reaction. These results shown that the adsorption of RBD removal is efficient using prepared adsorbent from Canna indica root tubers. Therefore, these CIBs could be used for other toxic dyes and heavy metals from industrial wastewater.

Efficient removal of methylene blue dye from aqueous solution using a new biosorbent derived from Ensete ventricosum (Enset)

In this study, kocho was prepared from pseudostem and corm of Ensete ventricosum (enset).The behaviors of kocho were examined by using FESEM, TGA, XRD and FTIR spectroscopy. The biosorption potential of kocho, a possible low-cost new biosorbent for the efficient removal of MB dye from wastewater was investigated. Biosorption experiments were carried out in batch mode to study the effects of biosorbent dosages (0.025-0.2 g), pH (2–10), initial concentrations of MB (10 to 100 mg/L) and contact time (10 to 120 min).The highest removal efficiency of methylene blue dye (94.2%) was recorded at optimum experimental conditions. Following the removal study, it was determined that the pseudo-second order kinetics (R2 = 0.997) and Langmuir isothermal (R 2= 0.996) models may well describe the MB dye biosorption process. Furthermore, this newly developed biosorbent was fairly recyclable up to five cycles without significant loss of re-adsorption efficiency (around 9.6% loss) between 1st and 5th cycle. Thus, the findings of this study revealed that a new kocho biosorbent derived from Ensete ventricosum can be used as a promising low-cost, environmentally friendly and efficient biosorbent for the rapid removal of MB from aqueous solutions.
 KEY WORDS: Kocho, Ensete ventricosum, Biosorption, Methylene blue, Kinetics, Isothermal
 Bull. Chem. Soc. Ethiop. 2024, 38(1), 69-84. DOI: https://dx.doi.org/10.4314/bcse.v38i1.6

Application of Response Surface Design for Optimization of Direct Red Dye Biosorption onto Cockleshells

This work emphasizes the efficiency of the response surface design to optimize the parameters affecting the removal of a textile dye—Direct Red 81 (DR-81)—by biosorption on seafood waste, namely, cockleshells (CS). The adsorbent was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analysis of surface and pH points of zero charge (pHpzc). A Box–Behnken design (BBD) with three factors was used to optimize the experimental conditions. After the experiment and data analysis, the optimal conditions found were 1 g of adsorbents, 10 mg/L of initial dye concentration, and a pH of 2 in the adsorbate solution, with the highest removal efficiency of 99.98%. The experimental results were analyzed by the ANOVA test, and they demonstrated the acceptability of the quadratic regression model. The adjusted determination coefficient R2 (adj) was equal to 98.82%, indicating an excellent relationship between the predicted and experimental responses. Langmuir isotherms were determined to be the best-fitting model, and the maximum adsorption capacity was 4.65 mg/g. The adsorption process was endothermic and fit the pseudo-second-order model. The negative values of ∆H and ∆S in the thermodynamic research showed that the bio-adsorption technique for the removal of Direct Red 81 is exothermic, spontaneous, and feasible. In addition, the negative value of ∆G indicates that the adsorption mechanism occurs at solid–liquid interfaces with an increasing number of species.

Thermally treated biomass of pine (Pinus kesiya) leaves for effective removal of organic dyes from aqueous solutions

AbstractBACKGROUNDMethyl orange (MO) and methylene blue (MB) from aqueous solutions were effectively removed using thermally treated pine (Pinus kesiya) leaves. The influences of solution pH (2–10), contact time (10–240 min) and initial dye concentration (100–500 mg L−1) were found to be significant in the process of dye removal. The experimental data were fitted with four isotherm models (Langmuir, Freundlich, Sips and Temkin) and four kinetic models (Elovich, pseudo‐first‐order, pseudo‐second‐order and intraparticle diffusion). Some mechanisms of the MO and MB adsorption onto the adsorbent material were proposed and discussed.ResultsAmong the four isotherm models examined, the experimental data gave the best fit with the Langmuir model. The maximum Langmuir adsorption capacities were 136.99 mg g−1 for MO and 140.85 mg g−1 for MB. Kinetic studies illustrated that the biosorption of both dyes onto pine leaves aligns with Elovich, pseudo‐first‐order, pseudo‐second‐order and intraparticle diffusion models. Thermodynamic studies showed that the uptake of the two dyes was regulated by physisorption, and it was spontaneous and endothermic in nature. Electrostatic interactions, as well as other noncovalent forces such as π–π interactions and hydrogen bonds, were mechanisms of dye adsorption on heat‐treated pine leaf biomass.ConclusionThe present study suggests that pine leaves could be a potential biosorbent for wastewater treatment due to their high availability and production, resulting in several environmental advantages. © 2023 Society of Chemical Industry (SCI).