Adsorbent Dosage Research Articles

Fabrication of tannic acid-incorporated polyvinylpyrrolidone/polyvinyl alcohol composite hydrogel and its application as an adsorbent for copper ion removal.

An effective tannic acid-incorporated polyvinylpyrrolidone/polyvinyl alcohol composite hydrogel with high-potential sorption capacity was developed for the removal of copper from aqueous solution. The composite hydrogel exhibited pH-dependent swelling, in which swelling and shrinking occurred reversibly with adjustment of the pH of the medium. At pH 4, the maximal adsorption capacity for copper at 30°C was 297.0mg g-1, and the adsorbent dose was 4g L-1. The adsorption kinetics were best fitted with a pseudo-second order kinetic model. The adsorption behavior was well predicted by the Freundlish isotherm. The thermodynamics parameters indicated a spontaneous and exothermic reaction with an increase in the entropy of the system. The chemical changes in the film structure before and after adsorption treatment were characterized by Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS). The FTIR, XPS and XAS results confirmed that Cu bound to the oxygens in the -OH, C = O and N-(C = O)- functional groups on the T-HD. XAS analysis revealed the chemical composition and molecular geometry of the adsorbed copper ions. The single-solute adsorption and coadsorption mechanisms, which provide insight into cobalt-copper, nickel-copper, or nickel-cobalt-copper complex solutions, were investigated. The composite hydrogel exhibited excellent regeneration ability in EDTA solution. Notably, the adsorbent retained an adsorption efficiency exceeding 87% even after five regeneration cycles. On the basis of both adsorbent characteristics and adsorption performance, it was determined that the composite hydrogel has the potential to be used as a platform for developing materials to treat wastewater containing high levels of metal contaminants such as those from the electroplating industry.

Kinetic modeling of the removal of phenolic compounds from olive mill wastewater by hierarchical zeolite/carbon nanotubes: Isotherm, kinetics, and thermodynamic

ABSTRACT In this study, plain zeolite (ZSM5) and hierarchical zeolite (H-ZSM5) were synthesized as efficient adsorbents for the removal of polyphenolic/antioxidant compounds from olive mill wastewater (OMW). The XRD and FTIR results confirmed the successful synthesis of ZSM5 zeolites. SEM images and BET demonstrated that H-ZSM5 possessed a markedly greater surface area of 337.99 m2/g in contrast to ZSM5 (162.84 m2/g). For H-ZSM5, the values determined for pore volume, total volume, and pore diameters are 77.655 cm3 g−1, 0.1844 cm3 g−1, and 2.1826 nm. The absolute zeta potential values varied between 5.36 ± 1.21 and − 46.41 ± 1.32 mV, with the peak absolute value of − 46.41 ± 1.32 mV occurring at pH 4. The optimal conditions for the removal of phenolic compounds, achieving an efficiency exceeding 90%, were identified as a pH of 4, an adsorbent dosage of 50 mg, and a contact duration of 90 minutes. The adsorption isotherm was found to align with the Langmuir model rather than the Freundlich model, indicating a monolayer adsorption capacity of 48.7 mg/g. Kinetic studies were consistent with a pseudo-first-order model (R2 >0.99). Ultimately, the thermodynamic analysis suggested that the adsorption of OMW onto ZSM5 is both spontaneous and governed by a physisorption mechanism.

Design and utilisation of a novel poly imino-phosphorane composite for the effective removal of Pb2+ and Cr3+ ions from contaminated water sources

ABSTRACT This study introduces a novel chitosan-immobilised imino-phosphorane composite (Chi-iph) for the efficient removal of lead (Pb2+) and chromium (Cr3+) from wastewater. The successful synthesis of Chi-iph was confirmed using FT-IR, XPS, BET, EDX, TGA, 1H-NMR, 13C-NMR, EI/MS, and ICP-OES analyses. Various experimental parameters such as pH, equilibrium time, metal concentration, adsorbent dose, temperature, and eluents were optimised to enhance the adsorption performance. At 25°C, with pH values of 5.5 for Pb2+ and 4.5 for Cr3+, an initial concentration of 200 mg/L, and an agitation time of 20 min, the maximum adsorption capacities were 55 mg/g for Pb2+ and 45 mg/g for Cr3+. Kinetic modelling demonstrated that the pseudo-first-order model best predicted the adsorption process, yielding capacities of 56.65 mg/g for Pb2+ and 46.38 mg/g for Cr3+. Isotherm analysis showed that the Langmuir model was a better fit than the Freundlich model, with theoretical capacities of 56.81 mg/g for Pb2+ and 44.64 mg/g for Cr3+. The Dubinin–Radushkevich (D-R) isotherm revealed adsorption energy (E) values of 9.45 kJ/mol for Pb2+ and 8.64 kJ/mol for Cr3+, indicating a chemisorption process. Theoretical saturation capacities (qD) were 56.28 mg/g for Pb2+ and 45.58 mg/g for Cr3+. Temkin isotherm results, with bT values of 9.71 and 8.53 kJ/mol for Pb2+ and Cr3+ respectively, aligned closely with the D-R model, further confirming chemisorption. Thermodynamic studies indicated that the adsorption process is exothermic, spontaneous, and more favourable at lower temperatures. Complete desorption of the heavy metals was achieved using 1 M HNO₃, allowing for efficient metal recovery. In a practical application, the Chi-iph composite removed 11.5 mg/L of Pb2+ and 7.01 mg/L of Cr3+ from contaminated wastewater, demonstrating its potential for environmental remediation. The composite’s performance aligns with WHO and FAO guidelines, making it suitable for treating wastewater before disposal into marine environments.

Efficient Removal of Cu(II) and Ni(II) Ions from Aqueous Solutions Using Reduced Graphene Oxide/Bentonite Clay/ZnO Nanocomposites: Kinetics, Mechanisms, and Adsorption Performance

<p style="text-align:justify;text-indent:36.0pt;"><span style="font-family:"Arial","sans-serif";font-size:11pt;line-height:150%;">To assess the efficacy of removing heavy metals such as Cu (II) and Ni (II) ions from aqueous solution, the adsorption behaviour of a nanocomposite powder comprising of reduced Graphene Oxide (rGO), bentonite clay, and ZnO was investigated. Various analytical techniques including Fourier transform infrared spectroscopy, Field emission scanning electron microscopy, Energy-Dispersive X-ray spectroscopy, X-Ray diffraction analysis, and N<sub>2</sub> adsorption/desorption analysis were utilized to analyse the synthesized composites. Through the batch equilibrium approach, parameters influencing adsorption behaviours, including initial metal ion concentration, pH, adsorbent dosage, and contact time, were comprehensively examined. Adsorption data were shown to have good fit to the Langmuir isotherm model and pseudo-first-order model, with high R<sup>2</sup>, low root mean square error (RMSE), low chi square (Χ<sup>2</sup>), and low standard deviation (SD) values when using the linear regression approach. For the raw sample (rGO/ bentonite clay) containing copper and nickel, equilibrium was achieved in 80 minutes, while for samples with 1% (rGO/ bentonite clay/1% ZnO), 3% (rGO/ bentonite clay/3% ZnO), and 5% (rGO/ bentonite clay/5% ZnO), equilibrium was attained within 70 minutes. </span><span style="background-color:white;font-family:"Arial","sans-serif";font-size:11pt;line-height:150%;">Within the pH range of 2 to 12, the adsorption kinetics of copper and nickel exhibited a notable pH-dependent relationship, highlighting the pronounced influence of pH conditions on the adsorption process</span><span style="background-color:white;color:#374151;font-family:"Segoe UI","sans-serif";font-size:11pt;line-height:150%;">. </span><span style="background-color:white;font-family:"Arial","sans-serif";font-size:11pt;line-height:150%;">Copper consistently demonstrated superior removal efficiency compared to nickel in all conducted adsorption tests, attributed to its heightened propensity for bond formation with adsorbent surfaces.</span><span style="font-family:"Arial","sans-serif";font-size:11pt;line-height:150%;"> The primary pathways for copper and nickel adsorption on the composites involved intermolecular interactions, cation exchange, physisorption and electrostatic interactions. The Langmuir model revealed maximum Cu (II) adsorption capacities of 312.5 mg/g, 217.39 mg/g, 161.95 mg/g, and 101.96 mg/g for raw sample, 1%, 3%, and 5% samples, respectively. Nickel (II) adsorption capacity were measured at 252.41 mg/g, 185 mg/g, 125.03 mg/g, and 96.60 mg/g for the raw sample, 1%, 3%, and 5% samples, respectively.</span></p>

Instant and efficient greenly silver nanoparticles for remediating atrazine and methylene blue from contaminated water.

In an attempt to create economically feasible and sustainable wastewater treatment "green" techniques, Malva parviflora leaf water extract was used for biosynthesizing silver nanoparticles (Malva-AgNPs). Fourier transform infrared, ultraviolet-visible (UV-Vis), scanning electron microscopy, and dynamic light scattering (DLS) were used for the characterization of Malva-AgNPs. UV-Vis and DLS analysis revealed the stability of the Malva-AgNPs at a wavelength of 420nm and an average size of 100nm ± 1nm. A zeta potential of - 26.4mV provides additional support for the stability of the material. The removal studies were conducted using atrazine and methylene blue (MB) in a single or mixed liquid state. The adsorbent dose, pH, incubation time, and pollutant concentration in the adsorption process were investigated. The optimal removal for 500mg L-1 of atrazine and MB at the adsorbent dosage of 450mg, when incubated for 5min, was found to be 99.5% and 82.03% for atrazine and MB, respectively. Also, Malva-AgNPs eliminated more than 95% and 50% of the atrazine and MB mixture, respectively, in 5min. The kinetics study showed that the pseudo-second-order kinetics model was a better fit for explaining the experimental adsorption experiments for atrazine and MB. The obtained equilibrium adsorption data were examined using the Langmuir and Freundlich isotherm models, which indicate that atrazine and MB have maximum adsorption capacities of 434.78mgg-1 and 400mgg-1, respectively.

Fabrication of Mesoporous SiO<sub>2</sub> Shells for Dye Adsorption Studies

The present work focuses on the fabrication of novel hybrid materials for toxic dye removal from an aqueous environment. Nanocarbon template (20-30 nm) was coated with tri-ethyl-orthosilicate (TEOS). The core-shell structure developed was further air pyrolyzed at 600 °C to produce mesoporous silica shells. The pore structures and characteristics of the material were evaluated using XRD, nitrogen adsorption studies, SEM, and TEM. Owing to the hierarchical porosity in range of 1-4 nm and 10-20 nm their adsorption studies were investigated for Phenol-Red. Dye adsorption studies performed revealed 98% removal efficiency with only 20 mg of adsorbent dose within 15 minutes.

Response Surface Methodology: A Review on Optimization of Adsorption Studies

Herein, we reviewed response surface methodology (RSM), a powerful statistical tool widely used in optimizing adsorption processes to remove synthetic dyes, toxic heavy metals, and phenols from wastewater. The widely used RSM models during optimization are the central composite design and Box-Behnken, which are second-order polynomial models. The models give a predictive insight into the number of experimental runs to be carried out. Furthermore, an in-depth overview of RSM and its application in optimizing various adsorption parameters, such as adsorbent dosage, initial pollutant concentration, contact time, and pH is discussed. In addition, RSM enables researchers to efficiently determine the optimal conditions for maximum pollutant removal. Lastly, the findings of this research highlight the potential of RSM as a valuable tool for optimizing adsorption processes and contributing to sustainable water treatment technologies.

Effect of Washing Temperature on Adsorption of Cationic Dyes by Raw Lignocellulosic Biomass

This study evaluated the potential of using raw Maclura pomifera and wild carob for the treatment of methylene blue (MB) and crystal violet (CV) as part of the search for new, abundant, and cost-effective natural materials applicable for wastewater treatment. Additionally, it explored the impact of washing water temperature on the adsorption performance of these raw organic materials. The physicochemical properties of the materials were characterized using BET, SEM/EDS, and FTIR analyses. The effects of various experimental parameters were investigated through batch adsorption experiments. The results demonstrated that the influence of washing water temperature was material-dependent. For Maclura pomifera, the maximum adsorption capacity of methylene blue and crystal violet decreased from 134.4 and 136.6 mg g−1 for MPC to 67.1 and 90.5 mg g−1 for MPH. In contrast, the adsorption capacities of wild carob biosorbents remained consistent, with the maximum amounts adsorbed for methylene blue and crystal violet by CC, CW, and CH being close, around 78.8 and 98.9 mg g−1, respectively, indicating a minimal effect of washing temperature on this material. The adsorption of both dyes onto the adsorbents was positively affected by increasing the pH, contact time, and initial dye concentration and was negatively affected by increasing adsorbent dose or ionic strength. Adsorption isotherms and kinetics were modeled using various mathematical approaches. The kinetic data were accurately described by a pseudo-second-order model, with a significant contribution from intraparticle diffusion. The Sips and Redlich–Peterson models provided the best fit for the adsorption isotherms of both dyes on the biosorbents. These findings confirm that the selected biomaterials are excellent adsorbents for the removal of cationic dyes.

Facile Synthesis of Polypyrrole-Decorated RGO-CuS Nanocomposite for Efficient Nickel Removal from Wastewater

Efficient wastewater treatment, particularly the removal of heavy metal ions, remains a challenging priority in environmental remediation. This study introduces a novel sandwich-structured nanocomposite, RGO-CuS-PPy, composed of reduced graphene oxide (RGO), copper sulfide (CuS), and polypyrrole (PPy), synthesized via a straightforward hydrothermal method. The unique combination of RGO, CuS, and PPy offers enhanced adsorption capacity for Ni(II) ions due to RGO’s high surface area and CuS’s active binding sites, supported by PPy’s structural stability contributions. This study is among the first to explore this specific nanocomposite architecture for Ni(II) removal, achieving an adsorption capacity of 166.67 mg/g and a high removal efficiency of 94.9% within 210 min for 55 mg/L of Ni(II) concentration at pH 6 and adsorbent dose of 3 mg/15 mL. The kinetic analysis shows the best fitted time-dependent experimental data with the pseudo-second-order model, indicating chemisorption. Isotherm studies confirmed the Langmuir model as the best fit, yielding a high monolayer adsorption capacity of 166.67 mg/g. Thermodynamic analysis shows the adsorption process was endothermic (ΔH° = 80.23 kJ/mol) and spontaneous (ΔG° ranging from −6.985 to −14.399 kJ/mol). Additionally, reusability tests using 0.1 M HCl for desorption demonstrated good reusability, emphasizing the RGO-CuS-PPy nanocomposite’s potential as a sustainable adsorbent for Ni(II) removal in wastewater treatment applications.

Electrospun nanofibers membranes of La(OH)3/PAN as a versatile adsorbent for fluoride remediation: Performance and mechanisms

Abstract Excessive existence of fluoride in water resources can lead to harmful impacts on ecosystems and organisms. Electrospun polyacrylonitrile (PAN) nanofiber membranes loaded with La(OH)3 nanorods composites (La(OH)3/PAN electrospun nanofiber membranes [ENFMs]) are fabricated and used as an efficient fluoride scavenger. Adsorbent fabricate protocols, pH, initial F− concentration, adsorbent dosage, and adsorption time, in addition to coexisting anions, were systematically evaluated. The investigation unveils that a pH of 3.0 is optimal for F− remediation. The adsorption kinetics and isotherm of La(OH)3/PAN ENFMs are well described by the pseudo-second-order model (R 2 > 0.997) with characteristics of chemisorption and Langmuir isotherm (R 2 > 0.999) with the feature of single-layer coverage. The existence of Cl−, SO4 2−, NO3 −, and CO3 2− does not significantly hinder fluoride removal by La(OH)3/PAN ENFMs with the exception of PO4 3−. Calculations of ΔH, ΔG, and ΔS reveal that the nature of F− adsorption onto La(OH)3/PAN ENFMs is endothermic and favorable at a higher temperature.

Application of a magnetic graphene nanocomposite modified with 5-aminoisophthalic acid amine group for chromium (VI) adsorption from aqueous solutions: kinetic and thermodynamic studies

ABSTRACT Polymer nanocomposites are composite materials that incorporate nanomaterials, such as magnetic graphene oxide (mGO), into a polymer matrix. To enhance its adsorption capacity, the surface of mGO nanoparticles was polymerised by a 5-aminoisophthalic acid amine group (mGO-AIPA) through a simplified co-precipitation method. The structural and morphological characteristics of the synthesised nanoparticles were evaluated through techniques such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), Thermogravimetric analysis (TGA), and Vibrating sample magnetometer (VSM). Response surface method (RSM) was used to evaluate the effectiveness of mGO-AIPA nanocomposite in removing chromium (VI) ions by examining variables such as solution of pH, contact time, adsorbent dose and initial concentration. Also, the study of kinetic models, adsorption isotherms and thermodynamic modelling of the process were evaluated. The results found that the mGO-AIPA nanocomposite has the maximum removal of chromium (VI) ions from the aqueous solution by 83.11% in optimal conditions including pH 3.5, contact time of 35 min, an adsorbent dosage of 25 mg g−1 and an initial concentration of 55 mg L−1. The pseudo-second-order kinetic and Langmuir isotherm models had a better fit with the experimental data of adsorption and the maximum adsorption capacity of chromium (VI) the base of the Langmuir model was 90.91 mg g−1. Moreover, the thermodynamic analysis indicated that the process was exothermic and nonspontaneous process, implying that it was energetically unfavourable. These findings suggest that the mGO-AIPA nanocomposite has a high performance as an effectual adsorbent to eliminate chromium heavy metal from an aqueous medium.

Zirconium-Modified Attapulgite Composite for Phosphorus Removal and Algae Control in Lake Water

Phosphorus removal is critical for effective water treatment and the prevention of eutrophication. This study focuses on the modification of attapulgite, an economical clay material, with zirconium (Zr@ATP) to enhance its phosphorus adsorption capacity. Zr@ATP was comprehensively characterized, and its phosphorus-removal mechanisms were investigated. Additionally, its performance in water treatment was evaluated using a lake water-sediment system. Zr@ATP exhibited a high surface area of 329.29 m2/g. The static adsorption experiments revealed that Zr@ATP achieved a phosphorus-removal efficiency of 95.8% at an adsorbent dosage of 5 g/L. Kinetic studies indicated that the adsorption followed a pseudo-second-order model, with the primary mechanism being chemisorption via ion exchange. Application of Zr@ATP in a lake water-sediment system resulted in an 83.6% reduction in total phosphorus. The chlorophyll concentration significantly decreased from 32.33 μg/L to 8.56 μg/L, and the algal density decreased by 84.6%, effectively inhibiting algal growth. These results suggest that Zr@ATP is a promising adsorbent for sustainable phosphorus removal and eutrophication control in aquatic environments.

Mineral Heterostructures for Simultaneous Removal of Lead and Arsenic Ions

This study focuses on Pb2+ and As(V) adsorption on mineral heterostructures based on a mixture of Si, Fe, and Ti oxides (MOHs). Various techniques were performed to analyze the morphological and structural properties of the synthesized metal oxide samples. In addition to the experimental optimization of the parameters determined by the response surface method (RSM), the effects of pH, adsorbent dosage, temperature, and contact duration on the batch and column system adsorption efficiency of single-component and simultaneous lead and arsenate removal were tested. The pseudo-second-order kinetic model and Weber–Morris model were more relevant to the adsorption on the metal(loid)s. The adsorption of Pb2+ was related to the Langmuir isotherm model, while the adsorption of As(V) was fitted to the Freundlich isotherm model. The thermodynamic parameters indicate the spontaneity of the adsorption process with a low endothermic character. The MOHs were more effective in removing Pb2+ and As(V) in the multi-component system (87.7 and 46.1%, respectively) than in the single-component system (56.3 and 23.4%, respectively). This study demonstrates that mineral heterostructures can be effectively used to remove cations and anions from water systems, and due to their fast kinetics, they can be applied to the needs of rapid interventions after pollution.

Synthesis of bagasse-derived magnetic biochar for the removal of fluoride from water solution

ABSTRACT Fluoride levels in drinking water pose a significant environmental threat, and adsorption is a common technique. However, many adsorbent materials have drawbacks such as poor adsorption capabilities, extended contact times, high pH levels, and large dosages. A biochar-based magnetic composite adsorbent has been developed for water defluoridation using a chemical co-precipitation process to immobilize iron particles on the biochar surface. X-ray diffraction analysis, Fourier transformed infrared spectroscopy, Brunauer–Emmett–Teller, and scanning electron microscopy were used to analyse the composite. The central composite design was used to design laboratory tests, which included four input variables: solution pH, dosage, contact time, and initial concentration. The adsorbent dosage was 5.92 g/L, the aqueous pH was 5.79, the contact time was 66.48 min, and the initial fluoride concentration was 12.38 mg/L. The removal efficiency was predicted to be 98.61%, with a 98.55% removal efficiency at optimum conditions. The study concluded that the composite adsorbent can be a reliable and sustainable solution for fluoride removal from water.

Low-cost Biochar from Parthenium Hysterophorus for Efficient Cr⁶⁺ Removal: A Sustainable Wastewater Treatment Solution

Aims: This study explores the development of innovative, cost-effective methods for removing Cr6+ from wastewater, focusing on biochar derived from Parthenium hysterophorus shoots. The biochar was prepared using a conventional slow-pyrolysis process and evaluated for its potential to treat Cr⁶⁺ in aqueous solutions. Study Design: Batch adsorption experiments are carried out in the study. Place and Duration of Study: The study was conducted in the Department of Environmental Science, G B Pant University of Agriculture & Technology, between Feb 2024 and July 2024. Methodology: Parthenium hysterophorus shoots were collected, reagents were purchased from HiMedia, and Cr⁶⁺ solutions were prepared and adjusted using NaOH and HCl. Shoots were washed, sun-dried, ground into powder and pyrolysed at 350°C for 180 minutes. Biochar yield was calculated, pH, proximal parameters (moisture, volatile matter, ash, fixed carbon) and ultimate analysis were measured, chemical functional groups by FTIR and morphology by XRD using Bruker D8 Advance was done. Cr⁶⁺ removal was studied using biochar adsorbent under varying pH, initial Cr6+ concentration, adsorbent dose and contact time, adsorption capacity (q) and removal percentage were then calculated. Results: Characterization techniques such as Fourier Transform Infrared (FTIR) spectroscopy and X-Ray Diffraction (XRD) confirmed the presence of multiple functional groups and crystalline structures, which contribute to its adsorption efficiency. Batch adsorption experiments were conducted to investigate the influence of prepared biochar dosage, initial Cr⁶⁺ concentration, pH and contact time. The optimal removal efficiency of 72.77% was achieved under conditions of pH 10, a biochar dose of 1 g/L, an initial Cr⁶⁺ concentration of 30 mg/L and a contact time of 72 hours. Conclusion: Although challenges remain in optimizing production and functionalization, this research highlights the potential of biochar for sustainable water treatment. Addressing production costs and practical challenges will further enhance its applicability, contributing to environmental sustainability efforts.

Chitosan impregnated sugarcane bagasse biochar for removal of anionic dyes from wastewater

Wastewater treatment is of utmost importance in providing all equitable and safe drinking water. In the present study, a chitosan impregnated sugarcane bagasse biochar SCNC biocomposite has been synthesized for the removal of Congo red (CR) dye from an aqueous solution. The SCNC biocomposite was thoroughly characterized through Brunauer, Emmett and Teller (BET) and N2 adsorption isotherm, point of zero charge (pHPZC), elemental analysis, Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric analysis (TGA) analysis. Moreover, SCNC biocomposite was further employed to remove CR dye from the aqueous solution in batch mode. The SCNC biocomposite could remove more than 95.0% of CR at an initial concentration of (100mgL− 1), adsorbent dosage (0.05 g), time (200 min), pH ~ 3. The SCNC biocomposite achieved maximum adsorption capacity of 170mgg− 1. The equilibrium adsorption data for CR dye were best fitted to the Langmuir isotherm model with R2, 0.999. The kinetic and isotherm were statistically investigated using the chi-square statistic (χ2 ), mean square error (MSE), and the sum of squares error (SSE) Because of the higher correlation coefficient (R2 ≥ 0.999) and lower error functions, the equilibrium CR adsorption isotherms for a single-dye system fit Langmuir and the PSO kinetic model. The thermodynamic studies revealed the spontaneous and endothermic nature of adsorption of CR dye onto SCNC biocomposite. The SCNC biocomposite can be regenerated up to the 5th cycle successfully. The mechanism of CR adsorption onto SCNC was elucidated.

Modeling and Optimization of Cadmium and Lead Adsorption onto Natural Pterocarpus santalinoides Fruit

The presence of heavy metals in wastewater has raised concern in developing countries because of their impact on human health and environmental ecology. Therefore, this study aims to remove cadmium and lead ions from wastewater using natural Pterocarpus santalinoides fruit through the adsorption method. The Box-Behnken design (BBD) of the response surface methodology (RSM) method was adopted to optimize the process variables such as contact time (20-100 min), adsorbent dose (0.1-0.5 g), initial metal ion concentration (10-50 mg/l), and temperature (30-70 °C). The ANOVA results clearly indicate that the linear model was not sufficient to best predict the removal performance of cadmium (R2 = 0.4009) and lead (R2 = 6353). The optimum conditions for the maximum Cd (94.81%) and Pb (89.23 %) adsorption onto the adsorbent were achieved at contact time (42.16 min), adsorbent dose (0.25 g), initial metal ion concentration (21.52 mg/l), and temperature (37.00 °C). According to the findings of the present work, Pterocarpus santalinoides shows to be a potential eco-friendly and cheap adsorbent for the removal of Cd and Pb from aqueous solutions. The BBD-RSM actual and predicted values of the Cd and Pb ions response show non-significant correlation, suggesting poor agreement between the two, revealing that the BBD-RSM model applied is not effective for the relationship between the four parameters examined in the Cd and Pb ions removal process.

Synthesis of cubic mesoporous silica SBA16 functionalized with carboxylic acid in a one-pot process for efficient removal of wastewater containing Cu2+: Adsorption isotherms, kinetics, and thermodynamics

Wastewater containing heavy metal ions, such as Cu2+, that are released into the environment will cause irreparable damage to the nature and human health of living. It is, therefore, absolutely crucial to remove these toxic ions from water. Herein, this paper utilizes the cyano group as a functional reagent to prepare carboxyl-functionalized SBA16 for adsorbing Cu2+ in water. In this paper, 2-cyanoethyltriethoxysilane is employed as a functionalizing reagent to prepare carboxyl-functionalized SBA16 through a one-pot method. The prepared material was characterized using various techniques, such as WXRD, TEM, FT-IR, and XPS. The results indicated that the introduction of the functionalizing reagent did not disrupt the original cage-like cubic mesoporous structure (Im3m symmetry) of SBA16. Crucial adsorption factors, namely pH, adsorbent dosage, Cu2+ initial concentration, and contact time, affecting the removal of Cu2+ were monitored and the optimum adsorption conditions were determined. Isotherm and kinetic investigations were conducted and a non-linear fitting method of experimental data was used to obtain isotherm and kinetic parameters. Maximum adsorption capacity reaches 181.3 mg g−1 was achieved in 60 min at pH = 3. Adsorption kinetics and adsorption isotherm followed the pseudo-second-order (R2 = 0.999) and Langmuir (R2 = 0.999) models, respectively. This suggests that the adsorption process primarily involves chemisorption and monolayer coverage. Thermodynamic parameters showed the spontaneous and endothermic nature of the adsorption process. After 5 cycles, the adsorbent still maintains a good adsorption capacity for Cu2+. This suggests promising applications for the adsorbent in treating wastewater containing Cu2+.

Simultaneous Removal of Strontium, Manganese, Lead and Arsenate from Wastewaters Using a Green and Low-Cost Adsorbent Derived from Nut Residues

The potential of a nut residue, activated only by physical means, to simultaneously adsorb Sr2+, Mn2+, Pb2+ and As5+ from contaminated waters was investigated. Mono-metal and multi-metal adsorption behavior and adsorption capacities by the solid material were compared for a range of initial metals concentrations, adsorbent dose, contact time and solution pH. The mechanisms of adsorption were examined by conducting structural, mineralogical and chemical analyses and applying two isotherm models to simulate experimental data. In the case of mono-metal adsorption, the maximum uptake of Sr2+ by the biochar was 12.3, of Mn2+ 23.8, of Pb2+ 24.7 and of As5+ 12.4 mg/g. In the case of multi-metal adsorption, the uptake of each metal was enhanced as the total ion flux density increased, revealing that there was no competition between these ions for biochar’s sorption sites. For an adsorbent dose of 2 g/L, the maximum adsorption capacity of biochar for Sr2+, Mn2+, Pb2+ and As5+ could be raised up to 47.6, 49.9, 25 and 48.7 mg/g, respectively. Potential adsorption mechanisms were chemical complexation or electron coordination between the metals and the biochar matrix, as well as mineral precipitation on the adsorbent surface.

Magnetic activated carbonaceous materials from sugarcane bagasse: Preparation, characterization, and hexavalent chromium removal

The presence of hexavalent chromium (Cr (VI)) in effluents remains a global concern due to its toxic properties. Even though adsorption has been employed for its removal from water, developing sustainable materials with higher adsorption capacities is still pivotal to tackling such contamination. In this study, two magnetic carbons (MC) were produced by hydrothermal carbonization (HTC) of sugarcane bagasse in the presence of iron (III) nitrate at 230 and 270 °C. Both MCs were thermochemically activated at 500 and 700 °C using KOH (1:2; w:w). The materials were characterized in terms of composition, structure, morphology, texture, and surface properties and then evaluated in adsorption studies of Cr (VI). After HTC, some iron phases such as α-Fe2O3, γ-Fe2O3, and Fe3O4 were observed, while thermochemical activation additionally revealed Fe0 and Fe4[Fe(CN)6]3. Activation increased the amount of meso- and macropores, specific surface area, pHzpc, surface hydrophilicity, and carbon and nitrogen contents. The adsorption kinetics study indicated that the pseudo-second-order model describes better the behavior of the materials. The investigation of adsorbent dose showed that doses below 1.00 g L−1 were more efficient in Cr (VI) removal. MC-230 and MC-270 thermochemically activated at 700 °C exhibited the highest Cr (VI) adsorption capacities (10.5 and 15.5 mg g−1, respectively). Therefore, the improved adsorption capacity for Cr (VI) of the materials thermochemically activated at 700 °C was mainly due to their enhanced textural properties.