Initial Adsorbate Concentration Research Articles

Preparation of low-cost biochar from discarded tea waste for aqueous phase removal of hexavalent chromium [Cr(VI)]: kinetics, isotherm, and recyclability analysis

ABSTRACT The paper reports the application of iron–Jatropha leaf extract functionalized biochar derived from discarded tea waste to remove hexavalent chromium from aqueous matrices. The surface of the FeJa@TB was prepared from discarded tea waste and was functionalized by FeSO4, FeCl3, and Jatropha leaf extract. The batch mode adsorption experiments with various experimental conditions such as pH, contact time, initial adsorbate concentration, and temperature, were conducted to evaluate the ability of the adsorbent to remove Cr(VI). Kinetics of the sorption were analyzed by fitting the sorption data on various models namely, pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. The kinetic study concluded that chemisorption was the chief mechanism for the adsorptive removal of Cr(VI) as the sorption followed a pseudo-second-order model. Sorption data fitted better to the Freundlich isotherm model, suggesting multilayer Cr(VI) coverage onto the biochar surface. Thermodynamic parameters ΔG°, ΔH°, and ΔS° were computed to observe the influence of temperature on the process of sorption. The study concluded that the adsorptive removal of Cr(VI) onto biochar was non-spontaneous and exothermic with fewer randomness at the solid–liquid interface. The prepared biochar was recyclable up to six times with insignificant removal efficiency loss.

Conjugated polymers decorated lignocellulosic nanocomposites for malachite green contaminated water remediation

Various novel conjugated polymer composites were synthesized via in situ chemical oxidative polymerization on lignocellulosic waste, notably Azadirachta indica sawdust. The composites, including Azadirachta indica/polyindole (AIS/PIn), Azadirachta indica/polyaniline (AIS/PAn), Azadirachta indica/polythiophene (AIS/PTh), and Azadirachta indica/polypyrrole (AIS/PPy), were investigated for their porous structure, ease of synthesis, unique adsorptive properties, and adjustable morphology. The synthesized composites were characterized using SEM/EDS, TEM/SAED, XRD, BET, TGA, and FTIR, revealing detailed insights into their structural and morphological features. The potential of these composites as efficient adsorbents for removing malachite green (MG) dye from water was a vital focus of this research. Batch experiments were conducted to assess the impact of various factors on adsorption, such as adsorbent/adsorbate contact time (0–280 min.), adsorbent dosage (0.4–20.0 g/L), initial adsorbate concentration (25–100 ppm), pH (2–13), and temperature (30–60 °C). The results indicate a remarkable removal efficiency of 89.98 % for MG with an initial concentration (Co) of 50 mg/L, achieved within 120 min using 0.4 g/L of AIS/PIn at a pH above 8.3. The Langmuir adsorption isotherm model provided the best fit for the experimental data, with maximum adsorption capacities of 384.61 mg g−1 for AIS/PIn, 344.82 mg g−1 for AIS/PAn, 277.77 mg g−1 for AIS/PTh, and 256.41 mg g−1 for AIS/PPy. This suggests monolayer adsorption. The adsorption kinetics conformed to a pseudo-second-order model, with the process being endothermic, feasible, and associated with positive entropy, thereby underlining its favorability and spontaneity. The desorption studies determined that 0.1 M HCl was the most effective desorbing agent compared to NaOH, NaCl, CH3COOH, and H2O. The spectral and effect of pH analyses suggested that the adsorption mechanisms might involve multiple interactions, prominently including electrostatic interactions, hydrogen bonding, π-π interactions, and n-π interactions. Based on the findings, it is submitted that the conjugated polymer decorated biomass composite adsorbents exhibit reasonable recyclability over multiple cycles, versatility, and potent efficacy as low-cost adsorbents for eliminating MG dye from aqueous systems.

Removal efficiency, metal uptake, and breakthrough curve of aqueous lead ions removal using olive stone waste

Olive industries generate olive stone waste (OSW), which is recognized as an organic contaminant. Jordan is one of the Mediterranean Sea countries that produces a large amount of these residues. Waste from olive stones could serve as a biosorbent. One of the most hazardous heavy metals produced in a variety of industries, including the production of paint and batteries, is lead ions. The purpose of this work is to remove lead ions using olive stone waste as a biosorbent by adsorption techniques. The effects of initial concentration, pH, adsorbent concentration, and contact time are covered in the first section of the adsorption parameters, which is comprised of batch studies. In the second section, the breakthrough curve study was carried out using a fixed bed adsorption column. Findings said that the ideal pH for highest removal efficiency was occurred at 6.8 acidity and the most promising removal efficiency, at 25 ± 2 °C and 1 g of adsorbent for every 0.25 L of solution, hit 82.5 % of the initial concentration of 9 mg/L while 1 g of adsorbate was adsorbed in 1.9 mg of adsorbent. The breakthrough study indicated that after 110 h of operation a 150 L of treated solution attained with maximum removal efficiency of 90 % for lead ions initial concentration of (18 mg/L).

A green and economic approach to synthesize magnetic Lagenaria siceraria biochar (γ-Fe2O3-LSB) for methylene blue removal from aqueous solution.

In the printing and textile industries, methylene blue (a cationic azo dye) is commonly used. MB is a well-known carcinogen, and another major issue is its high content in industrial discharge. There are numerous removal methodologies that have been employed to remove it from industrial discharge; however, these current modalities have one or more limitations. In this research, a novel magnetized biochar (γ-Fe2O3-LSB) was synthesized using Lagenaria siceraria peels which were further magnetized via the co-precipitation method. The synthesized γ-Fe2O3-LSB was characterized using FTIR, X-ray diffraction, Raman, SEM-EDX, BET, and vibrating sample magnetometry (VSM) for the analysis of magnetic properties. γ-Fe2O3-LSB showed a reversible type IV isotherm, which is a primary characteristic of mesoporous materials. γ-Fe2O3-LSB had a specific surface area (SBET = 135.30 m2/g) which is greater than that of LSB (SBET = 11.54 m2/g). γ-Fe2O3-LSB exhibits a saturation magnetization value (Ms) of 3.72emu/g which shows its superparamagnetic nature. The batch adsorption process was performed to analyze the adsorptive removal of MB dye using γ-Fe2O3-LSB. The adsorption efficiency of γ-Fe2O3-LSB for MB was analyzed by varying parameters like the initial concentration of adsorbate (MB), γ-Fe2O3-LSB dose, pH effect, contact time, and temperature. Adsorption isotherm, kinetic, and thermodynamics were also studied after optimizing the protocol. The non-linear Langmuir model fitted the best to explain the adsorption isotherm mechanism and resulting adsorption capacity ( =54.55mg/g). The thermodynamics study showed the spontaneous and endothermic nature, and pseudo-second-order rate kinetics was followed during the adsorption process. Regeneration study showed that γ-Fe2O3-LSB can be used up to four cycles. In laboratory setup, the cost of γ-Fe2O3-LSB synthesis comes out to be 162.75 INR/kg which is low as compared to commercially available adsorbents. The results obtained suggest that magnetic Lagenaria siceraria biochar, which is economical and efficient, can be used as a potential biochar material for industrial applications in the treatment of wastewater.

Green Synthesis of ZnO Nanoparticles for Efficient Cr(VI) Removal and Antioxidant/Microbial Properties

AbstractThe study focuses on fabrication of a cost‐effective Zinc Oxide nanoparticles (ZnONPs) adsorbent using Syngonium podophyllum leaves extract to remove hexavalent chromium (Cr6+) from synthetically prepared wastewater. Various spectroscopic techniques, including X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray analysis (EDX), and transmission electron microscopy (TEM), were used to characterize the ZnONPs. Fourier infra‐red spectroscopy (FTIR) detected that various organic compounds like flavonoids, terpenoids, and carboxylic acids acts as stabilizing and capping agent. The batch adsorption study was conducted to investigate the effects of Cr6+ adsorption time, pH, adsorbent concentration, and initial adsorbate concentration. The maximum adsorption capacity was 267.068 mg/g at 313 K. The Freundlich isotherm model was most suitable, indicating multilayer confiscation of Cr6+ on the heterogeneous surface. Chemisorption was identified as the mechanism of sequestration. Thermodynamic studies revealed that Cr6+ removal was spontaneous and feasible, with ΔG° values suggesting predominantly physisorption. Additionally, ZnONPs displayed strong antibacterial activity against S. aureus bacteria, making them a potential alternative to antibiotics. ZnONPs exhibited impressive antioxidant activity. Overall, ZnONPs synthesized through biosynthesis proved to be excellent nano‐sorbents, antioxidants, and biocompatible materials with promising applications in water remediation and healthcare.

Guar gum, Ulva lactuca L. biomass, and xanthan gum-based copolymer novel biosorbent for adsorptive removal of acid orange 10

The textile industry's wastewater discharge into water bodies has become a significant environmental concern due to its toxicity and adverse impact on the ecosystem. In response, this study presents the development of a highly effective adsorbent (GG@ULB@XG composites) by employing guar gum (GG), Ulva lactuca L. biomass (ULB), and xanthan gum (XG), using the ionic gelation method. Various characterization techniques including XRD, SEM, TGA, Zeta Sizer, Zeta Potential, BET, FTIR, and Point of Zero charge (pHPZC) were utilized to analyze the properties of the GG@ULB@XG composites. The removal efficiency of the composite for Acid Orange 10 dye was found to be exceptional, achieving a remarkable 93% removal rate. Optimal adsorption parameters were determined, including initial AO10 concentration (100 ppm), temperature (298K), pH (3), adsorbent concentration (100 mg), and contact time (15 min) at 480 λmax. The thermodynamic analysis provided valuable insights into the thermal stability of the adsorbent. Additionally, a comprehensive investigation of adsorption isotherms (linear and non-linear), such as Elovich, Freundlich, D-R, Langmuir, and Temkin Isotherms, was conducted to better understand the adsorption behavior. Various linear and non-linear adsorption kinetics models, including Elovich, first-order, interparticle diffusion, and second-order kinetic models, were employed to gain deeper insights into the chemistry of the adsorption process. This study highlights the potential of GG@ULB@XG composites as an effective and environmentally friendly solution for water treatment and dye removal in industrial wastewater and sets a foundation for future studies in the field of environmental remediation.

Adsorption of anionic wood dyes on KOH-activated carbons from Pinus radiata sawdust

AbstractChemically activated carbons synthesized from pine sawdust were applied efficiently for the elimination of wood dyes from aqueous solutions. Different proportions (1:2 and 1:4) of activating agent (KOH) and activation temperatures (600 and 850 °C) were used. Carbon surface morphology was characterized. The effect of pH (2–12), initial adsorbate concentration (5–500 mg L−1), and carbon dosage (0.1–0.5 g L−1) on dye adsorption were studied in batch mode. Langmuir model described well the adsorption equilibrium. The maximum found adsorption capacities were 1221.58, 1673.03, and 240.38 mg g−1 for blue and red at 500 mg L−1 and black at 100 mg L−1, respectively, using activated carbon at 850 °C and 1:4 (ACPS-4–850); at 25 °C, adsorbent dose 0.4 g L−1 for blue and black and 0.3 g L−1 for red dye and without change the pH for blue and red and at pH = 2 for black dye. The pseudo-second-order model explained the kinetics of adsorption except for the black dye at 100 mg L−1 using ACPS-4–850 for which it was the pseudo-first-order model. Desorption studies performed with ACPS-4–850 revealed that the adsorption was irreversible by chemical regeneration, whereas for the black dye, regeneration was efficient using H2O2 as desorbing agent.

ENHANCING BIOADSORPTION EFFICIENCY OF PEANUT SKIN BASED ON PHYSICAL AND CHEMICAL ACTIVATION METHODS IN FE2+ ION REMOVAL USING COLUMN TECHNIQUE IN ARTIFICIAL WASTEWATER

In the interest of efficient heavy metal ion removal from water, various methods such as aeration, coagulation, filtration, sedimentation, and adsorption have been thoroughly investigated. Adsorption, specifically the column method with groundnut shell powder as a bio adsorbent, stands out as a practical, effective, and efficient approach. In this study, a fixed variable of 50 g adsorbent, a particle size of 35 mesh, and an initial adsorbate concentration of 100 ppm was used, along with a 10-liter adsorbate volume and a flow rate of 4 liters per minute. Sampling intervals of 0, 15, 30, 45, 60, 75, 90, 105, 120, 135, and 150 minutes were chosen, and the independent variables encompassed untreated adsorbents, physically activated adsorbents, and chemically activated adsorbents using 1N H2SO4 and 1N NaOH. The outcomes revealed that the adsorption of Fe2+ was notably influenced by the type of activator. The highest Fe2+ removal percentage, 55.90%, was achieved at 135 minutes, showcasing the efficacy of the bioadsorption process. Notably, the optimal bioadsorbent activation was attained using 1N NaOH. This study provides valuable insights into the dynamics of heavy metal ion removal, emphasizing the significance of bioadsorption with groundnut shell powder and underscoring the impact of specific activation methods on the efficiency of the adsorption process.

Adsorptive uptake of thymol blue from aqueous medium using calcined snail shells: equilibrium, kinetic, thermodynamic, neuro-fuzzy and DFT studies

ABSTRACTS The spontaneous discharge of pollutants or toxicants into the ecosystem as a result of various anthropogenic activities is alarming, this necessitates a drastic cheap, and eco-friendly clean-up approach. Out of all the methods, adsorption has proven to be the most effective. The batch adsorptive removal of Thymol Blue (TB) dye from aqueous solutions is examined in this study utilizing calcined snail shells (CalSS). With the aid of SEM, EDS, XRD, and FTIR, the synthesized adsorbent was examined for different physicochemical characteristics. A machine learning model namely Adaptive Neuro-Fuzzy Inference System (ANFIS) was developed to assess the TB adsorption process while taking into account the important adsorption parameters contact time, temperature, pH, adsorbent dosage, then initial adsorbate concentration. Adsorbent pHpzc was also evaluated. EDX and FTIR confirm the formation of CaO with sharp peaks at 547 cm−1 and C–O and O–H are present. SEM and XRD show an irregularly shaped highly crystalline adsorbent material having a typical particle size of 65 ± 2.81 nm and lattice parameter value of 8.611617 Å. The pHpzc value is 11.04, indicating basic surface characteristics. The pH of 3.0, an adsorbent dose of 10 mg and the highest achievable adsorption efficiency were measured to be 98.75% at 20 °C. The findings from the study fit nicely onto Brouser Sotolongo with q BS = 259.4887 mg/g and R 2 = 0.9888. The pseudosecond order model (PSOM) recorded the least error value of 0.3336 and R 2 = 0.9952. This indicates chemisorption and multilayer adsorption processes. The thermodynamic parameters ΔH° and ΔG° demonstrate the exothermic and spontaneous nature of the adsorption process. The ANFIS model for the TB sequestration was evaluated using relevant statistical metrics, giving Root Mean Square Error (RMSE) value of 1.4644, Mean Absolute Deviation (MAD) value of 0.576, Mean Absolute Error (MAE) value of 1.2974 and Mean Absolute Percentage Error (MAPE) value of 1.5141. This outcome revealed that the ANFIS model and experimental findings are in good agreement. The efficacy of calcined snail shell in removing Thymol Blue dye from aqueous solution was also examined using in-silico technique which was in accordance to the value of the calculated descriptors obtained from the adsorbent as well as the calculated binding affinity. The elimination of TB-polluted wastewater using calcined snail shells is demonstrated in this study to be a successful and environmentally benign process.

Green synthesis of iron (III) oxide (Fe3O4) Nanoparticles Using Citrus sinensis Peel Extract for the Removal of Ciprofloxacin in Water

Ciprofloxacin is a widely used antibiotic that can contaminate water sources and pose environmental and health risks. Therefore, the objective of this paper is to explore the green synthesis of iron (III) oxide nanoparticles using Citrus sinensis peel extract for the removal of ciprofloxacin in water using standard techniques. The adsorption of ciprofloxacin on the nanoparticles was investigated under different conditions, such as pH, initial concentration of adsorbate, contact time, and different adsorbent doses. The adsorption data were fitted to different isotherm and kinetic models to understand the adsorption mechanism and parameters. The results of characterization revealed the particles to be of nanocrystalline structure with a cubic crystal shape, negative surface charge, and a high thermal stability with elemental composition primarily of Fe and O; it has z- average of 42.60, with Fe-O bond at 693.30cm-1 and UV-Visible absorbance at 221nm. The maximum adsorption capacity with ciprofloxacin was 29.21 mg/g (97.45%) at pH of 7 and room temperature of 25 °C. The results of the adsorption data indicated that the adsorption followed the Langmuir isotherm model and the pseudo-second-order kinetic model, suggesting a monolayer adsorption on a homogeneous surface with a finite number of identical sites. The synthesized nanoparticles showed a high efficiency and selectivity for the removal of ciprofloxacin from water, demonstrating it potential as an eco-friendly and low-cost adsorbent for water purification.

Custom and definitive screening designs for evaluating multiple adsorbents: bisphenol-A adsorption onto villi-structured polyaniline/carboxymethyl cellulose composites

ABSTRACT Polyaniline composites consisting of carboxymethyl cellulose (CMC) have enhanced adsorption properties, but recent studies indicate that the oxidised species – dialdehyde carboxymethyl cellulose (DCMC) – outperforms CMC-based composites. However, these studies fail to study the effect of DCMC's aldehyde content and compare the composites with CMC-based composites; numerous experiments required to investigate each adsorbent for each factor limit such studies. We explored a way to study whether villi-structured polyaniline (VSPANI), its CMC composite (CMC/PANI), and its DCMC composites with 35% (DCMC(A)/PANI) and 77% (DCMC(B)/PANI) aldehyde content would be great adsorbents for removing bisphenol-A (BPA). We first customised a D-optimal screening design to alleviate the pitfalls of definitive screening design (DSD), hence estimating all the main effects: initial concentration, pH, flow rate, adsorbent amount, sample volume and type of adsorbent. We excluded CMC/PANI and DCMC(A)/PANI composites, both with low adsorption capacities of 56.57 and 57.27 mg/g from further investigation. The DSD followed to estimate all second-order effects through which we projected a response surface method (RSM) to optimise and model the active factors. Increasing the aldehyde content on the composites favoured adsorption, but there lacked evidence to suggest VSPANI and DCMC(B)/PANI differed significantly in performance. The models were numerically and graphically proven adequate, explaining 80% and 99% of the variation when predicting removal efficiency and adsorption capacity. VSPANI showed potential as an adsorbent for BPA removal with 85% removal efficiency and 129 mg/g adsorption capacity. This comprehensive approach, combining both designs, allows for sustainable investigation of multiple adsorbents and factors, minimising experimental waste.

Remediation of toluidine blue O dye from aqueous solution using surface functionalized magnetite nanoparticles

Abstract In the current study, tannic acid-functionalized iron oxide nanoparticles have been synthesized using a cost-effective co-precipitation method and subsequently characterized using various instrumentation techniques such as Fourier transform infrared spectroscopy, X-ray diffractometer, field emission scanning electron microscopy, and thermal gravimetric analysis. Further, these surface-modified magnetite nanoparticles have been used for the adsorption of toluidine dye from an aqueous solution. The adsorption process was accompanied using batch procedure, and influences of several factors such as adsorbent dose, contact time, pH, temperature, and initial concentration of adsorbate were inspected concurrently. The maximum adsorption capacity of tannic acid-functionalized magnetite nanoparticles was found to be 50.68 mg/g. The adsorption process was observed to follow the Temkin isotherm model, whereas the kinetic study was well described by pseudo-second order. The thermodynamic study revealed the adsorption process to be endothermic and spontaneous in nature with a high degree of freedom between adsorbent and adsorbate. Therefore, the study indicated that the tannic acid-functionalized magnetite nanoparticles have promising adsorption capability and can be used as an excellent adsorbent for the removal of toluidine blue O dye from the aqueous solution.

Magnetic graphene derivates for efficient herbicide removal from aqueous solution through adsorption.

2,4-Dichlorophenoxyacetic acid (2,4-D) is an herbicide and is among the most widely distributed pollutant in the environment and wastewater. Herein is presented a complete comparison of adsorption performance between two different magnetic carbon nanomaterials: graphene oxide (GO) and its reduced form (rGO). Magnetic functionalization was performed employing a coprecipitation method, using only one source of Fe2+, requiring low energy, and potentially allowing the control of the amount of incorporated magnetite. For the first time in literature, a green reduction approach for GO with and without Fe3O4, maintaining the magnetic behavior after the reaction, and an adsorption performance comparison between both carbon nanomaterials are demonstrated. The nanoadsorbents were characterized by FTIR, XRD, Raman, VSM, XPS, and SEM analyses, which demonstrates the successful synthesis of graphene derivate, with different amounts of incorporate magnetite, resulting in distinct magnetization values. The reduction was confirmed by XPS and FTIR techniques. The type of adsorbent reveals that the amount of magnetite on nanomaterial surfaces has significant influence on adsorption capacity and removal efficiency. The procedure demonstrated that the best performance, for magnetic nanocomposites, was obtained by GO∙Fe3O4 1:1 and rGO∙Fe3O4 1:1, presenting values of removal percentage of 70.49 and 91.19%, respectively. The highest adsorption capacity was reached at pH 2.0 for GO∙Fe3O4 1:1 (69.98mgg-1) and rGO∙Fe3O4 1:1 (89.27mgg-1), through different interactions: π-π, cation-π, and hydrogen bonds. The adsorption phenomenon exhibited a high dependence on pH, initial concentration of adsorbate, and coexisting ions. Sips and PSO models demonstrate the best adjustment for experimental data, suggesting a heterogeneous surface and different energy sites, respectively. The thermodynamic parameters showed that the process was spontaneous and exothermic. Finally, the nanoadsorbents demonstrated a high efficiency in 2,4-D adsorption even after five adsorption/desorption cycles.

Absorbance Enhancement of a Treated Tanzanian kaolin for Removal of Synthetic Dyes from Water

The absorbance efficiency of local kaolin clay from Tanzania (Pugu kaolin) has been enhanced to improve its utilization in removal of textile dyes from water. The clay was acid-activated using H2SO4, after calcination at 750oC. Characterization by XRF, XRD, ATR-FTIR and Porosimeter showed kaolinite [Al2Si2O5(OH)4], silica (SiO2) and microcline [KAlSi3O8] as the main phases. Upon acid treatment, silica increased from 44.18% to 58.81% due to the appearance of tridymite, and alumina decreased from 26.70% to 12.74% due to disappearance of the kaolinite. Surface area increased from 15.36 to 149.61 m2 /g due to removal of acid-soluble impurities. The chemical composition showed decrease of Fe2O3 and increase of other major oxides. The impact of acid-activation on contact time, temperature, adsorbent dose, initial pH and absorbate concentration was investigated through batch adsorption technique using basic blue 9 (BB9) and direct red 28 (DR28) dyes. The results at optimal conditions of 3 hours contact time, 27oC temperature, 0.9 g adsorbent dose, initial pH of 11 and initial adsorbate concentration of 90 mg/L, showed that acid modification of the clay increased its capacity to adsorb BB9 from 96.82% to 99.91%, and DR28 from 86.33% to 95.04%. These findings established the influence of modifying the raw clay for its dye removal applications.

Adsorption Investigations on the Removal of Azoic Dye by Untreated Wood Sawdust

Batch adsorption of the azoic dye Congo red (CR) was carried out successfully on untreated low-cost wood sawdust. The impact of several variables (contact time, amount of solid adsorbent, initial adsorbate concentration, temperature, and pH) on the sorption process was studied. A maximum removal efficiency was achieved after 50 minutes at pH = 5 and 25 °C. To characterize the adsorbent, FTIR, SEM, EDX, and BET analyses were performed. The equilibrium isotherms were described using four alternative models. The data were found to fit the Freundlich model the best. The kinetic analysis demonstrates that the process is best represented by a pseudo-second-order model. The thermodynamic studies revealed the spontaneity and the exothermic nature of the sorption process. The optimal isotherm model served as the foundation for the design of a one-stage batch adsorber for the sorption of CR onto wood sawdust.

Batch adsorption study of Congo Red dye using unmodified Azadirachta indica leaves: isotherms and kinetics

Abstract A low-cost adsorbent developed from unmodified Azadirachta indica leaves was used for adsorptive removal of the Congo Red dye from an aqueous medium. The adsorbent was characterized by the Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), and scanning electron microscopy (SEM) techniques. For optimization of operational parameters such as dye concentration, solution pH, adsorbent dose, contact time, and temperature, batch adsorption experiments were performed. It was found that for neem leaves powder (NLP), the optimum conditions were as follows: adsorbent dose of 0.8 g, contact time of 100 min having a solution with pH value of 5, adsorbate initial concentration of 40 ppm at temperature 60 °C where maximum amount of dye, i.e., 84%, removal was observed. The process followed pseudo-first-order kinetics, which reveals physical adsorption. According to isothermal investigations, sorption data were best fit with the Freundlich isotherm model. Thermodynamically, the adsorption of the Congo Red dye by the neem leaf powder was exothermic. Furthermore, the mechanistic removal of the Congo Red dye by the NLP has been explored with the help of the surface complex formation (PHREEQC) mechanism. Overall, the results of the study explore the promising nature of NLP for Congo Red dye removal.

Evaluation of the adsorption capacity of surfactant-modified biomass in an aqueous acid blue 193 system

The study explored the capacity of modified pinewood dust (S-dust) for adsorbing acid blue 193 dye. The novel adsorbent was prepared via the insitu intercalation of quaternized ammonium copolymer (cationic surfactant) onto pinewood dust. The synthesized biosorbent was characterized using the Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersion X-ray (EDX) and Brunauer–Emmett–Teller (BET) surface area equipment. To establish the variable effects on the dye uptake, the ranges of solution pH, initial adsorbate concentration, contact time and adsorbent dosage were varied. The maximum monolayer adsorption capacity of 117.58 mg/g was recorded at pH 4.0, 0.1 g/L adsorbent dose and 2 h sorption duration. The process kinetics and isotherm modelling fitted best to the pseudo-first-order and Freundlich models, respectively. From the mechanistic/diffusion studies, intraparticle and pore diffusion mechanisms were respectively postulated at low and high initial adsorbate concentrations. Also, the occurrence of a nonspontaneous endothermic uptake process was inferred from the thermodynamics evaluations. Therefore, the effective acid blue 193 dye uptake onto novel S-dust was confirmed in this study.

The potential capability of treated perlite for removal of penta chloro nitrobenzene

Abstract Perlite is an example of clayey type geologic mineral. Perlite is a cheap and abundant adsorbent and it can be used for versatile applications in food, pharmacy and chemistry industries. Perlite was chosen for the removal of penta chloro nitrobenzene (PCNB) pesticide. This pesticide is used for the control of fungi species in farming commonly. Adsorbent surface area and pore volumes were determined as 288.15 m2/g and 78.24 cm3/g (BET method). The characteristics of the adsorbent were furnished by evaluating the SEM and FTIR images. The adsorption equilibrium was reached in 80 min. Initial adsorbate concentration and pH of the medium were also investigated from this point of view. The experimental data were evaluated with proper isotherm models such as Langmuir, Freundlich and Halsey. Langmuir and Freundlich isotherms give the best results. Monolayer capacity was found as 238.095 mg/g. The kinetic mechanisms of the phenomon was analyzed by employing the pseudo first and second order models. Pseudo first order kinetic results were better than the second one with the higher regression coefficients and close experimental and calculated uptake values. Those values were found as 0.615 and 0.6587 mg/g for 1 μg/mL aqueous pesticide solution. Activation energy was found approximately 5094 J/mol which was shown a physisorption mechanism of the adsorption. Activation energy is also employed for interpreting the sticking probability factor. The thermodynamic of adsorption were also evaluated and found as −2.385 J/g at the room temperature. The negative Gibbs energy shows the feasibility and spontaneous nature of PCNB removal on perlite.

Absorbance enhancement of a treated Tanzanian kaolin for removal of synthetic dyes from contaminated water

Kaolin possesses unique features suitable for removing pollutants from aqueous solutions, in this regard, improving its effectiveness as an adsorbent is important. This study focused on refining the absorbance efficiency of Pugu kaolin clay from Tanzania to enhance its utilization in removing textile dyes from contaminated water. The process involved acid-activation after calcination at 750oC. Characterization using X-ray Fluorescence (XRF), X-ray diffraction (XRD), Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Porosimeter techniques revealed the presence of kaolinite [Al2Si2O5(OH)4], silica (SiO2) and microcline [KAlSi3O8] as the main phases. Acid treatment resulted in an increase in silica content from 44.18% to 58.81% due to the appearance of tridymite, while alumina decreased from 26.70% to 12.74% due to the removal of kaolinite. Surface area significantly expanded from 15.36 to 149.61 m2/g as acid-soluble impurities were eliminated. Chemical composition was also altered, with a decrease in Fe2O3 and increase in other major oxides. The impact of acid activation on the adsorption capacity of the clay was investigated by studying various parameters such as contact time, temperature, adsorbent dose, initial pH and adsorbate concentration. Basic Blue 9 (BB9) and Direct Red 28 (DR28) dyes were used as model adsorbates. The results obtained at optimal conditions of 3 hours contact time, 27oC temperature, 0.9 g adsorbent dose, initial pH of 11 and initial adsorbate concentration of 90 mg/L, showed that acid modification of the clay increased its capacity to adsorb BB9 from 96.82% to 99.91%, and DR28 from 86.33% to 95.04%. These findings underscore the positive impact of modifying the raw clay, enhancing its suitability for dye removal applications.

Removing fluoride ions from wastewater by Fe3O4 nanoparticles: Modified Rhodophytes (red algae) as biochar

The present study seeks to utilize the biochar prepared from red algae (AR) and its composite with iron oxide (Fe3O4)-nanoparticle (MBC-AR) to estimate their batch extent potential decontamination mechanism for fluoride ion removal from aqueous solution. Various characterization techniques have been analyzed to study the functional groups, including FT-IR, XRD, EDS, SEM, FE-SEM, TEM and VSM of the synthesized adsorbent (MBC-AR). Several adequate batch adsorption studies were performed to ascertain the equilibrium state. The research yielded a well-established langmuir adsorption isotherm with a capacity for adsorption of 96.4 mg/g, and it suited well to a pseudo-second-order kinetic model. According to reports, the MBC-AR is a useful bio-adsorbent for eliminating fluoride ions from wastewater and other large-scale uses. At room temperature (298 K), the effects of bio-adsorbent doses (10–150 mg), initial concentration of adsorbate taken (20–80 mg/L), pH value (2.0–10.0), as well as contact time (0–250 min) were assessed for fluoride removal using MBC-AR. The efficacy of adsorption and its statistical data were well-established with a pseudo-second-order mechanism and Langmuir isotherm (R2 = 0.99). It was determined that the highest adsorption efficacy and capacity were 96.4 mg/g in the phase equilibrium process.