Azo dye adsorption on ZrO2 and natural organic material doped ZrO2

Natural wastes and inorganic adsorbents are used for the removal of diazo dye Congo red (CR), which causes water pollution and is a carcinogen, from wastewater. Organic waste olive pulp (ZK), inorganic ZrO2 (Zr) and three different weight percent ZK/Zr (organic/inorganic) binary adsorbent systems prepared by ball-milling method were investigated for the effective removal of CR from wastewater. Characterization of both single and binary adsorbent systems were carried out by ATR/FTIR and SEM. According to the Langmuir isotherm, qmax values for ZK, Zr, 25ZK-75Zr, 50ZK-50Zr and 75ZK-25Zr at 45 °C were 588 mgg-1, 13 mgg-1, 46 mgg-1, 65 mgg-1 and 84 mgg-1, respectively. According to Frumkin-Fowler-Guggenheim and Temkin isotherms, the adsorption heat was found to be exothermic for ZK and 75ZK-25Zr at all three temperatures, while it was found to be endothermic for Zr, 25ZK-75Zr and 50ZK-50Zr. It was observed that the ΔG° values calculated from the thermodynamic data were consistent with the values in the Flory-Huggings isotherm. According to the kinetic data, it was observed that all adsorbents except ZK obeyed the pseudo-first-order rate equation. It was shown by error calculations that the experimental data obeyed the Langmuir or Freundlich isotherms better. It was observed that a new and effective organic/inorganic adsorbent system could be obtained by adding ZK to ZrO2 for the removal of Congo red (CR) from water.

Preparation and modification of polymer microspheres, application in wastewater treatment: A review

The removal of various pollutants from water is necessary due to the increasing requirements for the removal of various pollutants from wastewater and the quality of drinking water. Polymer microspheres are regarded as exemplary adsorbent materials due to their high adsorption efficiency, excellent adsorption performance, and ease of handling. Herein, the advantages and disadvantages of different preparation methods, modifications, applications and the current research status of polymer microspheres are summarized at large. Furthermore, the enhanced performance of modified composite microspheres is emphasized, including adsorption efficiency, thermal stability, and significant improvements in physical and chemical properties. Subsequently, the current applications and potential of polymeric microspheres for wastewater treatment, including the removal of inorganic and organic pollutants, heavy metal ions, and other contaminants are summarized. Finally, future research directions for polymer microspheres are proposed, outlining the challenges and solutions associated with the application of polymer microspheres in wastewater treatment.

Bionanocomposite MIL-100(Fe)/Cellulose as a high-performance adsorbent for the adsorption of methylene blue

World production of dyes is estimated at more than 800,000 t·yr-1. The purpose of this research falls within the scope of the choice of an effective, local, and inexpensive adsorbent to remove dyes from wastewater. Adsorptive elimination of dyes by commonly accessible adsorbents is inefficient. The metal-organic frameworks (MOFs) are an important class of porous materials offering exceptional properties as adsorbents by improving separation efficiency compared to existing commercial adsorbents. However, its powder form limits its applications. One way to overcome this problem is to trap them in a flexible matrix to form a hierarchical porous composite. Therefore, in this work, we prepared MIL-100 (Fe) embedded in a cellulose matrix named MIL-100(Fe)/Cell, and used it as an adsorbent of methylene blue (MB) dye. According to the BET analysis, the specific surface area of the synthesized MOF is 294 m2/g which is related to the presence of the cellulose as efficient and green support. The structure of this composite is approximately hexagonal. Adsorption was studied as a function of contact time, adsorbent mass and pollutant load (concentration), and pH, and the effect of each of them on absorption efficiency was optimized. The MIL-100(Fe)/Cell was capable of removing 98.94% of MB dye with an initial concentration of 150 mg/L within 10 min at pH = 6.5 and room temperature. The obtained maximum adsorption capacity was 384.615 mg/g. The adsorption isotherm is consistent with the Langmuir models. The mechanism of MB adsorption proceeds through п-п and electrostatic interactions.

Construction of attapulgite decorated cetylpyridinium bromide/cellulose acetate composite beads for removal of Cr (VI) ions with emphasis on mechanistic insights

Eco-friendly and renewable composite beads were constructed for efficient adsorptive removal of Cr (VI) ions. Attapulgite (ATP) clay decorated with cetylpyridinium bromide (CPBr) was impregnated into cellulose acetate (CA) beads, which were formulated through a simple and cost-effective solvent-exchange approach. FTIR, XRD, SEM, Zeta potential, and XPS characterization tools verified the successful formation of ATP-CPBr@CA beads. The composite beads displayed a spherical and porous shape with a positively charged surface (26.6 mV) at pH 2. In addition, higher adsorption performance was accomplished by ATP-CPBr@CA composite beads with ease of separation compared to their components. Meanwhile, equilibrium isotherms pointed out that the Langmuir model was optimal for describing the adsorption process of Cr (VI) with a maximal adsorption capacity of 302 mg/g. Moreover, the D-R isotherm model verified the physical adsorption process, while adsorption data obeyed the pseudo-second-order kinetic model. Further, XPS results hypothesized that the removal mechanism involves adsorption via electrostatic interactions, redox reaction, and co-precipitation. Interestingly, the ATP-CPBr@CA composite beads reserved tolerable adsorption characteristics with a maximum removal present exceeding 70% after reuse for seven successive cycles, proposing its feasible applicability as a reusable and easy-separable candidate for removing heavy metals from aquatic bodies.

Preparation and characterization of P-type zeolite for adsorption of Cr3+, Ni2+, and Co2

Acid-washed coal fly ash (AW-CFA) was subjected to wet grinding activation followed by hydrothermal crystallization to synthesize P zeolite (FAZ-P). The FAZ-P obtained at 120 °C for 24 h exhibited a maximum relative crystallinity of 93.15% and was employed for the adsorption of Cr3+, Ni2+, and Co2+ from aqueous solutions. The zeolitization of coal fly ash (CFA) leads to an increase in specific surface area to 44.00 m2/g, resulting in the formation of nano-sized P zeolite crystals with uniformly narrow fissures and sizes within the range of 10-30 nm. Adsorption experimental results indicate that FAZ-P exhibits maximum adsorption capacities of 49.03 mg/g for Cr3+, 22.20 mg/g for Ni2+, and 27.25 mg/g for Co2+. The adsorption equilibrium data for both mixed and single-metal ion solutions conform to the Langmuir model, with the affinity sequence for heavy metal ions being Cr3+  > Co2+  > Ni2+. The pseudo-first-order and pseudo-second-order kinetic models effectively described the adsorption behavior of Cr3+, Ni2+, and Co2+. Increasing the initial pH value of the solution significantly enhanced the adsorption capacity of the adsorbent for heavy metal ions. The removal mechanism of metal ions involves both adsorption and ion exchange processes. The thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic.

A critical and comprehensive review of the current status of 17β-estradiol hormone remediation through adsorption technology

Even at low concentrations, steroid hormones pose a significant threat to ecosystem health and are classified as micropollutants. Among these, 17β-estradiol (molecular formula: C18H24O2; pKa = 10.46; Log Kow = 4.01; solubility in water = 3.90 mg L-1 at 27 °C; molecular weight: 272.4 g mol-1) is extensively studied as an endocrine disruptor due to its release through natural pathways and widespread use in conventional medicine. 17β-estradiol (E2) is emitted by various sources, such as animal and human excretions, hospital and veterinary clinic effluents, and treatment plants. In aquatic biota, it can cause issues ranging from the feminization of males to inhibiting plant growth. This review aims to identify technologies for remediating E2 in water, revealing that materials like graphene oxides, nanocomposites, and carbonaceous materials are commonly used for adsorption. The pH of the medium, especially in acidic to neutral conditions, affects efficiency, and ambient temperature (298 K) supports the process. The Langmuir and Freundlich models aptly describe isothermal studies, with interactions being of a low-energy, physical nature. Adsorption faces limitations when other ions coexist in the solution. Hybrid treatments exhibit high removal efficiency. To mitigate global E2 pollution, establishing national and international standards with detailed guidelines for advanced treatment systems is crucial. Despite significant advancements in optimizing technologies by the scientific community, there remains a considerable gap in their societal application, primarily due to economic and sustainable factors. Therefore, further studies are necessary, including conducting batch experiments with these adsorbents for large-scale treatment along with economic analyses of the production process.

Optimization and characterization of silver nanoparticle-modified luffa for the adsorption of ketoprofen and reactive yellow 15 from aqueous solutions

In the current work, luffa was modified with silver nanoparticles to prepare LF/AgNPs adsorbent for the elimination of ketoprofen and reactive yellow 15 (RY15) from aqueous media. Various characterization techniques, including FT-IR, XRD, BET, and SEM-EDS analysis, were employed to confirm the successful modification of LF/AgNPs. Several key parameters such as contact time, adsorbent dosage, concentration, pH, and agitation technique were fine-tuned to optimize the adsorption process. Ketoprofen removal was found to be most effective in weakly acidic conditions (pH = 5), while reactive yellow 15 adsorption was enhanced in an acidic environment (pH = 2). At 298 K, the highest adsorption capacities reached 56.88 mg/g for ketoprofen and 97.76 mg/g for reactive yellow 15. In both scenarios involving the elimination of ketoprofen and RY15, the Temkin isotherm exhibits higher R2 values, specifically 0.997 for ketoprofen and 0.963 for RY15, demonstrating a strong correlation with the observed adsorption data. Additionally, the kinetics of ketoprofen adsorption were best described by the Pseudo-first order model (R2 = 0.989), whereas the Pseudo-second order model provided the most accurate fit for reactive yellow 15 adsorption (R2 = 0.997). Importantly, the LF/AgNPs adsorbent displayed consistent performance over five consecutive reuse cycles, affirming its stability and efficacy in removing both contaminants. These findings underscore the exceptional potential of LF/AgNPs as a reliable adsorbent for the removal of reactive yellow 15 and ketoprofen from aqueous solutions.

Surface activity, kinetics, thermodynamics and comparative study of adsorption of selected cationic and anionic dyes onto H3PO4-functionalized bagasse from aqueous stream

The discharge of dyes into the water body creates toxicity to aquatic organisms because of their aromatic structure and difficult degradation. So, the treatment of dye-contaminated wastewater is required before releasing it. In the present study, thermally treated (600 °C) and H3PO4 (55%)-functionalized bagasse, henceforth called thermochemically activated bagasse (TCAB), was synthesized as potential adsorbent for the effective removal of selected cationic and anionic dyes from their aqueous stream. TCAB characterization was done employing FT-IR, SEM, XRD, zeta potential, BET, and PZC techniques. The comparative study shows that the relative adsorption on TCAB followed the sequence, methyl red (185 mg/g) > safranin (178 mg/g) > congo red (146 mg/g) > brilliant green (139 mg/g) > malachite green (130 mg/g) > bromocresol green (94 mg/g). The adsorption efficiency was investigated concerning the effect of change in TCAB dose (0.05-0.3 g/100 mL), initial dye concentration (20-200 mg/L), pH (4.0-10.0), ionic strength (0.1-0.5 M KCl), urea concentration (0.1-0.5 M) and temperature (25-45 °C). The representative adsorption isotherms belong to typical L-type. The time-dependent dye removal was best explained by the pseudo-second-order (PSO) kinetic model (R2 = 0.9859-0.9991), while equilibrium data were best explained by the Freundlich model (R2 = 0.9881-0.9961). Thermodynamic study showed the spontaneous (ΔG0 <0) and exothermic nature (ΔH0 <0) of the adsorption of different cationic and anionic dyes. The cyclic adsorption ability of TCAB for different dyes was checked up to three cycles (185 to 168 mg/L for MR, 178 to 165 mg/L for SF, 146 to 130 mg/L for CR, 139 to 127 mg/L for BG, 130 to 114 mg/L for MG and 94 to 80 mg/L for BCG), and no significant decrease in the adsorption capacity was noticed. So, the present study provides valuable insights into the adsorption of cationic and anionic dyes onto H3PO4-functionalized bagasse. Addressing the adsorptive aspects enhances the clarity, reliability and applicability of the study's findings and contributes to its overall scientific impact.

Sequestration of steroidal estrogen in aqueous samples using an adsorption mechanism: a systemic scientometric review

Steroidal estrogens (SEs) remain one of the notable endocrine disrupting chemicals (EDCs) that pose a significant threat to the aquatic environment in this era owing to their interference with the normal metabolic functions of the human body systems. They are currently identified as emerging contaminants of water sources. The sources of SEs are either natural or synthetic active ingredients in oral contraceptive and hormonal replacement therapy drugs and enter the environment primarily from excretes in the form of active free conjugate radicals, resulting in numerous effects on organisms in aquatic habitats and humans. The removal of SEs from water sources is of great importance because of their potential adverse effects on aquatic ecosystems and human health. Adsorption techniques have gained considerable attention as effective methods for the removal of these contaminants. A systemic review and bibliometric analysis of the application of adsorption for sequestration were carried out. Metadata for publications on SE removal utilizing adsorbents were obtained from the Web of Science (WoS) from January 1, 1990, to November 5, 2022 (107 documents) and Scopus databases from January 1, 1949, to November 5, 2022 (77 documents). In total, 137 documents (134 research and 4 review articles) were used to systematically map bibliometric indicators, such as the number of articles, most prolific countries, most productive scholars, and most cited articles, confirming this to be a growing research area. The use of different adsorbents, include activated carbon graphene-based materials, single and multi-walled carbon nanotubes, biochar, zeolite, and nanocomposites. The adsorption mechanism and factors affecting the removal efficiency, such as pH, temperature, initial concentration, contact time and adsorbent properties, were investigated in this review. This review discusses the advantages and limitations of different adsorbents, including their adsorption capacities, regenerative potential, and cost-effectiveness. Recent advances and innovations in adsorption technology, such as functionalized materials and hybrid systems, have also been highlighted. Overall, the bibliographic analysis provides a comprehensive overview of the adsorption technique for the removal of SEs from other sources, serving as a valuable resource for researchers and policymakers involved in the development of efficient and sustainable strategies to mitigate the effects of these emerging contaminants.

Enhanced phosphate adsorption studies on several metal-modified aluminum sludge: preparation optimization, adsorption behavior, and mechanistic insight

To solve the problems such as water eutrophication caused by excess phosphorus, the potential residual value of aluminum sludge was fully exploited and its phosphate adsorption capacity was further improved. In this study, twelve metal-modified aluminum sludge materials were prepared by co-precipitation method. Among them, Ce-WTR, La-WTR, Y-WTR, Zr-WTR, and Zn-WTR showed excellent adsorption capacity for phosphate. The adsorption performance of Ce-WTR on phosphate was twice that of the native sludge. The enhanced adsorption mechanism of metal modification on phosphate was investigated. The characterization results showed that the increase in specific surface area after metal modification was 9.64, 7.5, 7.29, 3, and 1.5 times, respectively. The adsorption of phosphate by WTR and Zn-WTR was in the accordance with Langmuir model, while the others were more following the Freundlich model (R² > 0.991). The effects of dosage, pH, and anion on phosphate adsorption were investigated. The surface hydroxyl groups and metal (hydrogen) oxides played an important role in the adsorption process. The adsorption mechanism involves physical adsorption, electrostatic attraction, ligand exchange, and hydrogen bonding. This study provides new ideas for the resource utilization of aluminum sludge and theoretical support for preparing novel adsorbents for efficient phosphate removal.

GO-CuO nanocomposites assimilated into CA-PES polymer membrane in adsorptive removal of organic dyes from wastewater

Textile industries are one of the leading environmental pollutants by releasing harmful dye effluents. In many textile distrts, the amount of excess color in treated textile effluent that exceeds regulatory limitations is still being a major concern. The combining usage of nanomaterials and polymer material to solve these issues using various techniques. In this research, graphene oxide-copper oxide (GO-CuO) nanomaterial have been incorporated into cellulose-acetate (CA), poly-ether sulfone (PES) blend polymer by using phase inversion process to fabricate thin film nanocomposite (TFN) membrane for removal of dye pollutant. The physiochemical properties of prepared TFN materials were studied by Fourier transform infra-red spectroscopy (FT-IR), X-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), thermo gravimetric analysis (TGA), and mechanical strength analysis. Dye adsorption experiments were performed with four typical water-soluble organic dyes methylene blue (MB), rhodamine blue (Rh. B), methyl orange (MO) and Congo red (CR). After reaching adsorption equilibrium, the composite membrane final removal effectiveness for MB 92.42%, Rh. B 89.39%, CR 68.39%, and MO 58.82% respectively. As a result, the fabricated TFN material proves to be an effective adsorbent material for cationic dye molecules. Also, when the fabricated material was tested with textile industry effluent sample, all physio-chemical properties exhibited a considerable decrease in concentrations when compared to the real textile effluent concentration. The treated effluents permitted for a relatively greater growth and germination index of Tropical amaranth roots than the textile effluent, this demonstrates that phytotoxicity testing was also successful. The most effective temperature, concentration and pH were found to be 273 K, 1 × 10^-5 M and pH 9. The fabricated TFN membrane material (GO-CuO @ CA-PES) can be recommended for water treatment applications.

Preparation and Adsorption Properties of Magnetic Molecularly Imprinted Polymers for Selective Recognition of 17β-Estradiol

In this paper, magnetic molecularly imprinted polymers (MMIPs) were fabricated on the surface of Fe3O4 by surface molecular imprinting technology, which can selectively adsorb 17β-estradiol (E2). The optimized experiments demonstrated that MMIPs possessed the best adsorption capacity when methanol was used as the solvent and MAA was used as the crosslinking agent, with a molar ratio of E2: MMA: EGDMA as 1:4:50. SEM, FTIR, and XRD were employed to investigate the morphologies of MMIPs and the results demonstrated that the MMIPs that can selectively adsorb E2 were successfully prepared on Fe3O4 particles. The adsorption experiments showed that 92.1% of E2 was adsorbed by the MMIPs, which is higher than the magnetic non-molecularly imprinted polymers (MNIPs). The Freundlich isotherm model was more suitable to describe the adsorption process of E2 by MMIPs. Meanwhile, MMIPs had a better recognition ability for E2 and its structural analogs such as estrone and estriol. The MMIPs still had good adsorption performance after methanol regeneration five times. The prepared MMIPs had the advantages of efficient adsorption ability and high reusability, so they can be applied for selective recognition and removal of E2.

Carbon Nanotubes/Polydopamine/ZSM-5 Composite Soil Conditioner with Good Controlled Release and Adsorption Properties

Currently, the excessive application of fertilizers and the random discharge of waste water, waste gas, and residues have led to more and more serious soil pollution problems. Zeolite is the most promising material for preparing a green and environmentally friendly soil conditioner. Herein, the carbon nanotubes/polydopamine/ZSM-5 composite soil conditioner was prepared by a facile two-step method, and it was used to release fulvic acid and adsorb methylene blue to improve the environment. The cumulative release rate of the composite soil conditioner was 52% within 430 h for fulvic acid, which had a good sustained release effect and could be sustained-released in different acid-based surroundings. In addition, it showed a good adsorption capacity of methylene blue, and it is about 80.02 mg/g which was about six times higher than that of ZSM-5. It was beneficial for the adsorption of methylene blue in a neutral environment. Finally, it could promote the growth of brassica chinensis and maize, and the promotion effect was 60 and 35%, respectively. Therefore, the carbon nanotubes/polydopamine/ZSM-5 composite soil conditioner is a green and efficient material, which provides a new strategy to solve the problem of soil pollution.

Nitrate adsorption onto surface-modified red mud in batch and fixed-bed column systems: equilibrium, kinetic, and thermodynamic studies

This research aimed to develop a novel composite as a low-cost adsorbent for the removal of nitrate ion from aqueous solutions. The characterization of this composite (composition of red mud with dimethyldioctadecylammonium bromide (DDAB)) was performed by XRF, XRD, FTIR, and BET analyses. The most influential variables on nitrate adsorption, including contact time, solution acidity, adsorbent amount, and temperature were studied. The maximum amount of nitrate adsorbed onto the prepared adsorbent was obtained at pH 5.5 and contact time 30 min. The heterogeneous adsorption occurred during the uptake of nitrate. The results of kinetic study revealed that intra-particle diffusion was the major limitation for nitrate adsorption rate. The values of thermodynamic parameters illustrate the non-spontaneous, associative, and exothermic adsorption process. Increasing the temperature enhances the tendency of the process to non-spontaneously. Research on fixed-bed column has been done under different initial nitrate concentrations. The adsorption capacity of nitrate was increased with an increase in the initial concentration of nitrate. The results of column data were successfully explained using the Thomas and Yoon-Nelson models.

Endosulfan Elimination Using Amine-Modified Magnetic Diatomite as an Adsorbent

Pesticides are among the most dangerous developing toxins since they are very hazardous to the environment and threaten human health. In this study, researchers successfully manufactured surface-modified magnetic diatomite (m-DE-APTES) and used them as a sorbent to extract endosulfan from an aqueous solution. There is no other study like it in the scholarly literature, and the results are astounding. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), electron spin resonance (ESR), and surface area measurements were used to analyze magnetic diatomite particles with surface modification. According to the analysis results, magnetic diatomite has a wide surface area and a porous structure. Furthermore, m-DE-APTES has a higher endosulfan adsorption capacity (97.2 mg g⁻¹) than raw diatomite (DE) (16.6 mg g⁻¹). Adsorption statistics agree with Langmuir adsorption isotherm (R² = 0.9905), and the adsorption occurred spontaneously at −2.576 kj mol⁻¹ in terms of ΔG^o. Finally, m-DE-APTES are a viable alternative adsorbent for removing pesticides from aqueous solutions.

A Multifunctional Microspheric Soil Conditioner Based on Chitosan-Grafted Poly(acrylamide-co-acrylic acid)/Biochar

A multifunctional microspheric soil conditioner based on chitosan-grafted poly(acrylamide-co-acrylic acid)/biochar [CS-g-P(AM-co-AA)/BC] was prepared. First, the P(AM-co-AA) was synthesized and successfully grafted onto CS, and the three-dimensional network structure of microspheres was formed with N,N-methylenebis(acrylamide) as the cross-linking agent according to the inverse suspension polymerization method. Meanwhile, BC and urea were encapsulated into the body of microspheres during the polymerization. The structure of the microspheres was analyzed by Fourier transform infrared spectroscopy, polarized optical microscopy, and scanning electron microscopy, and the mechanism of adsorption of Cu²⁺ on the microspheres was investigated by X-ray photoelectron spectroscopy. Furthermore, the experimental results demonstrated the excellent water absorption and retention capabilities of microspheres, and the release rate of urea was dramatically reduced. Importantly, the introduction of BC significantly enhanced the adsorption performance of the microspheres with respect to heavy metal ions. Consequently, the multifunctional soil conditioner held promise for use in soil improvement and agricultural production.

Antibiotic Removal from the Aquatic Environment with Activated Carbon Produced from Pumpkin Seeds

Antibiotics are among the most critical environmental pollutant drug groups. Adsorption is one of the methods used to eliminate these pollutants. In this study, activated carbon was produced from pumpkin seed shells and subsequently modified with KOH. The adsorbent obtained through this procedure was used to remove ciprofloxacin from aqueous systems. Fourier Transform-Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), elemental, X-ray Photoelectron Spectroscopy (XPS), Brunauer–Emmett–Teller (BET) and Zeta analyses were used to characterize the adsorbent. The surface area, in particular, was found to be a very remarkable value of 2730 m²/g. The conditions of the adsorption experiments were optimized based on interaction time, adsorbent amount, pH and temperature. Over 99% success was achieved in removal operations carried out under the most optimal conditions, with an absorption capacity of 884.9 mg·g⁻¹. In addition, the Langmuir isotherm was determined to be the most suitable model for the adsorption interaction.

Microporous activated carbon developed from KOH activated biomass waste: surface mechanistic study of methylene blue dye adsorption

In this work, sugarcane bagasse waste (SBW) was used as a lignocellulosic precursor to develop a high-surface-area activated carbon (AC) by thermal treatment of the SBW impregnated with KOH. This SBW activated carbon (SBWAC) was characterized by crystallinity, porosity, surface morphology and functional groups availability. The SBWAC exhibited Type I isotherm which corresponds to microporosity with high specific surface area of 709.3 m²/g and 6.6 nm of mean pore diameter. Further application of SBWAC as an adsorbent for methylene blue (MB) dye removal demonstrated that the adsorption process closely followed the pseudo-second order kinetic and Freundlich isotherm models. Conversely, a thermodynamic study revealed the endothermic nature and spontaneity of MB dye adsorption on SBWAC with high acquired adsorption capacity (136.5 mg/g). The MB dye adsorption onto SBWAC possibly involved electrostatic interaction, H-bonding and π-π interaction. This work demonstrates SBW as a potential lignocellulosic precursor to produce high-surface-area AC that can potentially remove more cationic dyes from the aqueous environment.

Performance of activated carbons prepared from spent tyres in the adsorption of rhodamine B in aqueous solutions

Activated carbons were produced from spent tyre pyrolysis char by steam or CO₂ activation and evaluated for their performance in rhodamine B (RhB) adsorption in aqueous solutions. The effect of RhB starting concentration (80-150 mg L^-1), contact time (0-80 min), temperature (298-318 K) and initial pH on the adsorption process was examined. Pseudo-first-order and pseudo-second-order models were carried out to fit the experimental data to derive RhB adsorption kinetics. Langmuir, Freundlich and Temkin isotherm models were applied to depict RhB adsorption behaviour of the prepared activated carbons. Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) were calculated. It has been found that the activated carbons can effectively adsorb RhB due to high mesoporosity and RhB equilibrium adsorption capacity (q_e) increased almost linearly with increasing total mesopore volumes, regardless of the activation agents. When BET surface areas are similar, CO₂-activated carbon obtained higher q_e than steam due to higher mesoporosity of CO₂-activated carbon. The results show that pseudo-second-order well fitted the experimental data. RhB starting concentration increased from 80 to 150 mg L^-1 causing q_e increased from 158 to 251 mg g^-1 but RhB removal decreased from 99.7 to 84.5%. The RhB adsorption process follows the Langmuir model and thermodynamic calculation, indicating RhB adsorption is an endothermic, spontaneous process, dominated by both chemisorption and physisorption.

Water-soluble polymeric particle embedded cryogels: Synthesis, characterisation and adsorption of haemoglobin

Making cryogels, which are among today’s accepted adsorbents, more functional with different methods, has been one of the subjects spent overtime. In this study, water-soluble poly(maleic anhydride-alt-acrylic acid) polymer embedded in poly(2-hydroxyethyl methacrylate) cryogels. Copper ions were then immobilised to this structure, and this polymer was used for adsorption of haemoglobin from aqueous systems. Adsorption interaction was carried out on an electrostatic basis, and approximately 448.62 mg haemoglobin/g polymer adsorption capacity value was obtained. It was found that the same material has managed to maintain its adsorption ability by 90.3% even after the use of it five times in the adsorption/desorption cycle. The adsorption interaction was determined to be appropriate for the Langmuir model by isotherm studies. The change in Gibbs free energy value was calculated as −2.168 kJ/mol.