Improvement of activated carbon characteristics by sonication and its application for pharmaceutical contaminant adsorption

Valorization of a poultry industry floated sludge as a raw material to produce char and activated carbon for pharmaceutical compounds adsorption

This study was intended to valorize a floated sludge of a poultry slaughterhouse using it as a precursor to producing char and activated carbon, which were tested as adsorbents in removing ketoprofen and diclofenac sodium from the water. The addition of zinc chloride or calcium hydroxide was determinant for forming a porous carbonaceous structure with a high surface area in AC-FSP (656.54 m2 g-1), differently from that exhibited by the CHAR-FSP (8.11 m2 g-1). Kinetic and equilibrium studies indicated that the pseudo-second-order and the Sips models were suitable. The AC- FSP maximum adsorption capacity for ketoprofen and diclofenac sodium was 124.98 mg g-1 and 138.32 mg g-1, respectively. The adsorption was a spontaneous and endothermic process. It was concluded that AC-FSP is a more efficient and promising adsorbent than CHAR-FSP for the adsorption of drugs in contaminated wastewater. In addition, AC-FSP can be reused, maintaining good adsorption levels for about 5 cycles. Therefore, this study is aligned with the 2030 Agenda for global sustainability since converting waste (valueless) into an adsorbent is also directly linked to the circular economy and neutral carbon.

Elimination of aspirin and paracetamol from aqueous media using Fe/N-CNT/β-cyclodextrin nanocomposite polymers: theoretical comparative survey via advanced physical models

The main purpose of this research is to theoretically investigate the adsorption of two pharmaceutical molecules, i.e. aspirin and paracetamol, using two composite adsorbents, i.e. N-CNT/β-CD and Fe/N-CNT/β-CD nanocomposite polymers. A multilayer model developed by statistical physics is implemented to explain the experimental adsorption isotherms at the molecular scale, so as to overpass some limitations of the classical adsorption models. The modelling results indicate that the adsorption of these molecules is almost accomplished by the formation of 3 to 5 adsorbate layers, depending on the operating temperature. A general survey of the number of adsorbate molecules captured by the adsorption site (n_pm) suggested that the adsorption process of pharmaceutical pollutants is multimolecular and that each adsorption site can capture several molecules simultaneously. Furthermore, the n_pm values demonstrated the presence of aggregation phenomena of aspirin and paracetamol molecules during adsorption. The evolution of the adsorbed quantity at saturation confirmed that the presence of Fe in the adsorbent enhanced the removal performance of the investigated pharmaceutical molecules. In addition, the adsorption of the pharmaceutical molecules aspirin and paracetamol on the N-CNT/β-CD and Fe/N-CNT/β-CD nanocomposite polymer surface involved weak physical type interactions, since the interaction energies do not overcome the threshold of 25 000 J mol^-1.

Insight into the adsorptive removal of ibuprofen using porous carbonaceous materials: A review

Over the last decade, the removal of pharmaceuticals from aquatic bodies has garnered substantial attention from the scientific community. Ibuprofen (IBP), a non-steroidal anti-inflammatory drug, is released into the environment in pharmaceutical waste as well as medical, hospital, and household effluents. Adsorption technology is a highly efficient approach to reduce the IBP in the aquatic environment, particularly at low IBP concentrations. Due to the exceptional surface properties of carbonaceous materials, they are considered ideal adsorbents for the IBP removal of, with high binding capacity. Given the importance of the topic, the adsorptive removal of IBP from effluent using various carbonaceous adsorbents, including activated carbon, biochar, graphene-based materials, and carbon nanostructures, has been compiled and critically reviewed. Furthermore, the adsorption behavior, binding mechanisms, the most effective parameters, thermodynamics, and regeneration methods as well as the cost analysis were comprehensively reviewed for modified and unmodified carbonaceous adsorbents. The compiled studies on the IBP adsorption shows that the IBP uptake of some carbon-based adsorbents is significantly than that of commercial activated carbons. In the future, much attention is needed for practical utilization and upscaling of the research findings to aid the management and sustainability of water resource.

Cassava bagasse as an alternative biosorbent to uptake methylene blue environmental pollutant from water

Herein, the methylene blue (MB) biosorption from the agroindustrial residue (cassava bagasse) is reported. The cassava bagasse residue presented an irregular surface, anionic character, and low specific surface area. The experiments were performed in batch mode. The biosorption behavior was investigated through the experimental variables, initial concentration of MB, pH, and temperature. The maximum biosorption capacity (170.13 mg g^-1) reached 328 K and pH 10.0. The equilibrium and kinetics were better fitted by the Sips and general order (R² ≥ 0.997 and R²_adj ≥ 0.996) models, respectively. Furthermore, the thermodynamic study revealed a spontaneous (ΔG⁰ < 0) and endothermic process. Finally, the results showed cassava bagasse is a potential material for biosorption dyes from the aqueous medium. In addition, the biosorbent has a low aggregate cost and high availability, which contributes to the destination of large amounts of waste and inspires engineering applications.

Adsorption of recalcitrant contaminants of emerging concern onto activated carbon: A laboratory and pilot-scale study

According to the World Health Organization (WHO), the definition of water quality indicators, including contaminants of emerging concern (CECs), associated with the development of multi-barrier approaches for wastewater treatment, are crucial steps towards direct potable reuse of water. The aims of this study were 1) quantifying twelve CECs (including pharmaceutical, stimulant, and artificial sweetener compounds) in both untreated and treated wastewater samples in a Brazilian wastewater treatment plant (WWTP) using bidimensional liquid chromatography coupled with tandem mass spectrometry, allowing the selection of five marker (i.e., priority) CECs; 2) evaluating the adsorption potential of such selected CECs [caffeine, hydrochlorothiazide, saccharin, sucralose (SUC), and sulfamethoxazole (SMX)] onto coconut-shell granular activated carbon (GAC); and 3) investigating the removal of the same CECs by a multi-barrier system (pilot-scale, 350 L h^-1) treating the effluent of the WWTP and composed of reverse osmosis (RO), photoperoxidation (UV/H₂O₂), and filtration with GAC. Such technologies were tested separately and in binary or ternary combinations. Eleven and eight CECs were detected and quantified on the untreated and treated wastewater samples of the Brazilian WWTP, respectively. For the treated wastewater, the concentrations ranged from 499 ng L^-1 (SMX) to 87,831 ng L^-1 (SUC). The adsorption onto AC data fitted the Sips isotherm model, indicating monolayer chemisorption, which was also suggested by the mean adsorption energy values (>16 kJ mol^-1). SMX and SUC were the most and the least adsorbed CECs (4.33 and 1.21 mg g^-1, respectively). Concerning the pilot-scale treatment plant, the ternary combination (RO + UV/H₂O₂+GAC) removed >99% of the five marker CECs and promoted reductions on water color, turbidity, as well as on nitrogen and phosphorus concentrations. Further studies on water reuse could prioritize the selected marker CECs as quality indicators. While the removal of marker CECs is one of the WHO performance requirements, the RO + UV/H₂O₂+GAC system showed promising results as a first approach to direct potable reuse of water.

Easy and Low-Cost Method for Synthesis of Carbon–Silica Composite from Vinasse and Study of Ibuprofen Removal

Vinasse was successfully utilized to synthesize carbon–silica composite with a low-cost silica source available in Thailand (sodium silicate, Na2SiO3) and most commonly used source, tetraethyl orthosilicate (TEOS). The composites were prepared by a simple one-step sol–gel process by varying the vinasse (as carbon source) to silica source (Na2SiO3 or TEOS) weight ratio. The resulting composites were characterized by N2 adsorption, moisture and ash contents, pH, pHpzc, bulk density, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX). The composites had highest surface area of 313 and 456 m2/g, with average mesopore diameters of 5.00 and 2.62 nm when using Na2SiO3 and TEOS as the silica sources, respectively. The adsorption of a non-steroidal anti-inflammatory drug, ibuprofen, was investigated. The contact time to reach equilibrium was 60 min for both composites. The adsorption kinetics were fitted by a pseudo-second-order model with the correlation coefficient R2 > 0.997. The adsorption isotherms were well described by the Langmuir model (R2 > 0.992), which indicates monolayer adsorption. The maximal adsorption capacities of the Na2SiO3- and TEOS-based composites were as high as 406 and 418 mg/g at pH 2, respectively. The research results indicate that vinasse and a low-cost silica source (Na2SiO3) show great potential to synthesize adsorbents through a simple method with high efficiency.

Adsorption of basic fuchsin using soybean straw hydrolyzed by subcritical water

The valorization of agro-industrial residues can be improved through their full use, making the production of second-generation ethanol viable. In this scenario, hydrolyzed soybean straw generated from a subcritical water process was applied to the basic fuchsin adsorption. At pH eight, a high adsorption capacity was obtained. The mass test results showed that basic fuchsin's removal and adsorption capacity could be maximized with an adsorbent dosage of 0.9 g L-1. The linear driving force model was suitable for predicting the kinetic profile, and the kinetic curves showed that equilibrium was reached with only 30 min of contact time. Besides, the Langmuir model was the best to predict the adsorption isotherms. The thermodynamic parameters revealed a spontaneous and endothermic process. At 328 K, there is maximum adsorption capacity (72.9 mg g-1). Therefore, it can be stated that this material could be competitive in terms of adsorption capacity coupled with the idea of full use of waste.

A new alternative of a green polymeric matrix chitosan/alginate-polyethyleniminemethylene phosphonic acid for pharmaceutical residues adsorption

A new generation of a green polymeric matrix, chitosan/alginate-polyethyleniminemethylene phosphonic acid (CHIT/ALG-PEIMPA) was examined in comparative study of adsorption and preconcentration of non-steroidal anti-inflammatory drugs (NSAIDs), diclofenac and ibuprofen. The influences of experimental parameters like pH, time reaction, initial concentration, ionic strength were investigated. The scanning electron microscopy (SEM) images showed heterogeneous morphology with different particle sizes of agglomerates from few micrometers to a hundred micrometers and irregular particles shape, before pharmaceuticals products adsorption. However, after adsorption, SEM micrograph reveals a smooth surface structure of agglomerate, and even in this smaller magnification, it was possible to observe the formation of homogenous and regular surface of CHIT/ALG-PEIMPA. Elementary analysis (EDX) reveals that the phosphonic acid (PEIMPA) was successfully cross-linked onto chitosan/alginate. The maximal adsorption capacity was found to be 222 mg.g^-1, and 122 mg.g^-1 under optimum conditions for diclofenac and ibuprofen respectively. The kinetic modeling followed the pseudo-second-order rate expression for both pharmaceutical drugs. Thermodynamics data leads to an exothermic and spontaneous adsorption processes (∆H = -34.32 KJ mol^-1; ∆H =-21.59 KJ mol^-1), respectively for diclofenac and ibuprofen.

Saturated adsorption of lidocaine and coal tar dyes onto porous polytetrafluoroethylene

Polytetrafluoroethylene (PTFE) has excellent physical properties and has been used in a wide range of applications in various fields. Adsorption research on PTFE is essential as primary research for the further application of PTFE. We attempted to adsorb coal tar dyes and model drugs such as lidocaine onto PTFE as a guideline to search for medicines that adsorb onto PTFE. Saturation curves were obtained after analyzing the adsorption of coal tar dyes on PTFE using the Hanes-Woolf plot. In addition, we collected multiple cases of ATR-FTIR spectral changes and/or retention depending on TPM derivatives and other adsorbates. Lidocaine matched some coal tar dye for the apparent spectral changes between the adsorbed molecules and its crystalline powder. The apparent spectral changes are blue-shifted, suggesting a hydrophobic interaction between the dyes/lidocaine and porous PTFE. This work provides a promising strategy for further application of PTFE.

Removal of anti-inflammatory drugs using activated carbon from agro-industrial origin: current advances in kinetics, isotherms, and thermodynamic studies

Nonsteroidal anti-inflammatory drugs (NSAIDs) are highly consumed around the world and consequently found as emerging pollutants in water; they are found in concentrations up to µg L−1 making their removal a priority. In this matter, adsorption is an efficient alternative for drug removal, so using activated carbon (AC) as an adsorbent is a highly explored subject. The current interest is to obtain AC from waste, for example, those of agro-industrial origin, reducing this way the overall costs of the process. Although information regarding the use of AC from agro-industrial origin in the removal of NSAIDs is limited, an exclusive compilation is required to understand the state of the art to date. This work aims to update information related to the adsorption of ibuprofen, diclofenac, and naproxen on agro-industrial AC, and it is focused on the period 2016–2021. It highlights the characteristics of agro-industrial AC responsible for efficient adsorption. Recent adsorption studies, including kinetics, isotherms, and thermodynamics, are analyzed and compared. Progress on removing NSAIDs from real wastewater is also presented and finally proposed adsorption mechanisms and costs related to these removal processes.

Optimization of ketoprofen adsorption from aqueous solutions and simulated effluents using H2SO4 activated Campomanesia guazumifolia bark

This study used the bark of the forest species Campomanesia guazumifolia modified with H₂SO₄ to absorb the anti-inflammatory ketoprofen from aqueous solutions. FTIR spectra confirmed that the main bands remained after the chemical treatment, with the appearance of two new bands related to the elongation of the carbonyl group present in hemicellulose. Micrographs confirmed that the surface started to contain a new textural shape after acid activation, having new pores and cavities. The drug adsorption's optimum conditions were obtained by response surface methodology (RSM). The adsorption was favored at acidic pH (2). The dosage of 1 g L^-1 was considered ideal, obtaining good indications of removal and capacity. The Elovich model very well represented the kinetic curves. The isotherm studies indicated that the increase in temperature negatively affected the adsorption of ketoprofen. A maximum adsorption capacity of 158.3 mg g^-1 was obtained at the lower temperature of 298 K. Langmuir was the best-fit isotherm. Thermodynamic parameters confirmed the exothermic nature of the system (ΔH⁰ = -8.78 kJ mol^-1). In treating a simulated effluent containing different drugs and salts, the removal values were 35, 50, and 80% at 15, 30, and 180 min, respectively. Therefore, the development of adsorbent from the bark of Campomanesia guazumifolia treated with H₂SO₄ represents a remarkable alternative for use in effluent treatment containing ketoprofen.

Numerical investigation of ibuprofen removal from pharmaceutical wastewater using adsorption process

In the present study, a mathematical modelling was developed to investigate ibuprofen adsorption from pharmaceutical wastewater into activated carbon and sonicated activated carbon. The developed model was dissolved based on the finite element method. Effect of different operating parameters including particle porosity and diameter as well as ibuprofen diffusion coefficient in solution on the amount of ibuprofen adsorption at different time point and position in the particle were evaluated. It was found good agreement between experimental values and modelling results in terms of ibuprofen adsorption as a function time. The 84.5% and 92.5% of maximum adsorption was achieved for the AC and SAC at the centre of particle after 150 min. Increasing the particle porosity and ibuprofen diffusion coefficient was improved the ibuprofen adsorption into the adsorbent. However, the particle diameter had negative impact on the system performance. There was a decrease in solute adsorption from 84.10 to 7.30 mg/g and from 106 to 15.73 mg/g for the AC and SAC respectively with increasing the particle radius from 173 to 500 µm. Finally, it was concluded that the particle specifications play important role in the adsorption process as it was observed considerable change in the amount of adsorption at different positions in the particle with changing the particle specifications.

Biosorption of ketoprofen and diclofenac by living cells of the green microalgae Chlorella sp

There is a growing interest for the removal of different pharmaceuticals from water owing to their toxicity to various organisms. The present study investigated the use of living cells of the green alga Chlorella sp. in the short-term adsorption of ketoprofen (KET) and diclofenac (DIF) from aqueous solutions. The bioremoval efficiency of both KET and DIF was highly dependent on various parameters such as time, pH, algal dosage, and drug concentration. The adsorption efficiencies of both KET and DIC were maximized at pH 6. The biosorption of KET was better described by pseudo-first-order kinetics, while DIC obeyed the pseudo-second-order model. The maximum adsorption capacities of KET and DIF were attained as 0.328 and 0.429 mg g^-1, respectively. The equilibrium data of the investigated drugs showed a better fit to the Freundlich model than the Langmuir model. The Elovich and Temkin models indicated that the algal surface was heterogeneous with different binding energies, while the intraparticle diffusion model assumed a boundary layer effect. Additionally, the Dubinin-Radushkevich isotherm indicated that the adsorption process was predominantly physisorption. FT-IR analysis revealed that H-bonding and n-π interactions were prominent in the biosorption process of the investigated pharmaceuticals on the surface of microalgae. The results of the present study showed that microalgae living cells could be applied as an eco-friendly and cost-effective biosorbent for the removal of KET and DIF at low concentrations.

High Selectivity and Reusability of Biomass-Based Adsorbent for Chloramphenicol Removal

Recently, biomass-based materials have attracted increasing attention because of their advantages of low cost, environment-friendly and nonpollution. Herein, the feasibility of using corn stalk biomass fiber (CF) and Fe₃O₄ embedded chitosan (CS) as a novel biomass-based adsorbent (CFS) to remove chloramphenicol (CAPC) from aqueous solution. Structure of CFS was characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM) and zeta potential techniques. The effects of solution pH, adsorption time and ion strength on the adsorption capacity were examined. Adsorption isotherms obtained from batch experiments were better fitted by Langmuir model compared with Freundlich model, Dubinin–Radushkevich model and Temkin model. Adsorption kinetic data matched well to the pseudo-second order kinetic model. CAPC adsorption was endothermic, spontaneous, and entropy-increasing nature on CFS. In addition, the CFS could be separated by an external magnetic field, recycled, and reused without any significant loss in the adsorption capacity of CAPC. Based on these excellent performances, there is potential that CFS can be considered as a proficient and economically suitable material for the CAPC removal from the water environment.

Efficient and selective removal of Ag+ as nano silver particles by the composite of SiO2 supported nano ferrous oxalate

Developing novel environmentally materials with high capacity and selectivity for Ag⁺ adsorption by transforming Ag⁺ to nano silver is important for the recovery of precious metals from Ag-containing solution. The present study systematically studied the Ag ⁺ adsorption process from solution by the composite of SiO₂ supported nano ferrous oxalate (SNFO) synthesized from biotite-containing minerals. Batch experiments, dynamics and isothermal adsorption fitting results showed that Ag⁺ removal behaviours were in accordance with the pseudo-first-order kinetic model and Langmuir model, and the maximal Ag⁺ removal capacity was 223.68 mg/g. Thermodynamic fitting results suggested that Ag ⁺ removal by the composite was a spontaneous and endothermic reaction process. XRD and TEM revealed that the reaction products were consisted of SiO₂ and nano silver particles, and FTIR and XPS results indicated that the Ag⁺ removal mechanisms were attributed to the synergistic reduction interaction between ferrous and the anions of oxalate. Meanwhile, the composite possesses high selectivity for Ag⁺ removal even at low Ag⁺ concentration. Moreover, the size of nano silver particles could be adjusted by different pH values. All above results demonstrated that the composite was an ideal material for selective recovery of Ag⁺ from Ag⁺ containing effluents in the form of nano silver.

Understanding the solid-liquid equilibria between paracetamol and activated carbon: Thermodynamic approach of the interactions adsorbent-adsorbate using equilibrium, kinetic and calorimetry data

In this work, we presented the paracetamol-activated carbon interactions and their effect on the adsorption capacity. We evaluated kinetic, equilibrium, and calorimetric data using different solvents (water, HCl 0.1 M, and NaCl 0.1 M) to evaluate the changes in the adsorbent-adsorbate interaction. In addition, the commercial activated carbon (AC) was modified through thermal (ACTT) and chemical (ACNA) methods to change the physicochemical properties of the adsorbents. The relative kinetic constants decrease with the content of basic groups on the activated carbon, indicating a lower influence of diffusion on the adsorption rate when the chemical interactions increase (0.1 _ACNA >0.09 _AC >0.03 _ACTT mmol g^-1). The adsorption capacity for AC at acidic pH increases slightly compared to tests carried out in the water. Under this condition, the adsorbed amount of paracetamol was 1.31 mmol g^-1. However, the maximum adsorption capacity was achieved on ACTT using water as solvent (1.57 mmol g^-1). The paracetamol adsorbed decreases in NaCl (osmotic, ionic strength) on all activated carbons by around 20%. The interaction enthalpy of the paracetamol-activated carbon interaction presents values between - 18.0 and 2.3 J per molecule adsorbed. The Gibbs energy released during the adsorption process is between - 33.1 and - 29.8 kJ mol^-1.

Novel Correlations between Spectroscopic and Morphological Properties of Activated Carbons from Waste Coffee Grounds

Massive quantities of spent coffee grounds (SCGs) are generated by users around the world. Different processes have been proposed for SCG valorization, including pyrolytic processes to achieve carbonaceous materials. Here, we report the preparation of activated carbons through pyrolytic processes carried out under different experimental conditions and in the presence of various porosity activators. Textural and chemical characterization of the obtained carbons have been achieved through Brunauer–Emmett–Teller (BET), ESEM, 13C solid state NMR, XPS, XRD, thermogravimetric and spectroscopic determinations. The aim of the paper is to relate these data to the preparation method, evaluating the correlation between the spectroscopic data and the physical and textural properties, also in comparison with the corresponding data obtained for three commercial activated carbons used in industrial adsorption processes. Some correlations have been observed between the Raman and XPS data.

Removal of ibuprofen from aqueous media by adsorption: A comprehensive review

Ibuprofen (IBP) is a non-steroidal anti-inflammatory drug released into the environment through hospital and medical effluents, pharmaceutical wastewater and veterinary use. The aim of this paper is to review the empirical findings on the adsorption of IBP from aqueous media. A preliminary ecotoxicological assessment confirmed the environmental risk of IBP in the aqueous environment. Open literature works considered in this review were for the past decade (2010-2020). Carbon-based adsorbents are the best class of adsorbent for the uptake of IBP and the highest reported maximum adsorption capacity (q_max) for IBP is 496.1 mg/g by SWCNTs. The range of adsorption capacities for IBP uptake in this review is between 0.0496 and 496.1 mg/g. The mechanism of uptake is majorly by hydrophobic interactions, π - π stacking, hydrogen bonds, electrostatic interactions and dipole-dipole interaction. IBP uptake was best fit to a wide variety of isotherm models but was well suited to the pseudo-second order kinetics model. The thermodynamics of IBP uptake depends majorly on the nature of the adsorbent and desorption from the solid phase is based on an appropriate choice of the eluent. Knowledge gaps were observed in used adsorbent disposal and process improvement. In the future, interest would increase in scale-up, industrial applications and practical utilisation of the research findings which would help in sustainable water resource management.

Preparation and Application of Efficient Biobased Carbon Adsorbents Prepared from Spruce Bark Residues for Efficient Removal of Reactive Dyes and Colors from Synthetic Effluents

Biobased carbon materials (BBC) obtained from Norway spruce (Picea abies Karst.) bark was produced by single-step chemical activation with ZnCl2 or KOH, and pyrolysis at 800 °C for one hour. The chemical activation reagent had a significant impact on the properties of the BBCs. KOH-biobased carbon material (KOH-BBC) had a higher specific surface area (SBET), equal to 1067 m2 g−1, larger pore volume (0.558 cm3 g−1), more mesopores, and a more hydrophilic surface than ZnCl2-BBC. However, the carbon yield for KOH-BBC was 63% lower than for ZnCl2-BBC. Batch adsorption experiments were performed to evaluate the ability of the two BBCs to remove two dyes, reactive orange 16 (RO-16) and reactive blue 4 (RB-4), and treat synthetic effluents. The general order model was most suitable for modeling the adsorption kinetics of both dyes and BBCs. The equilibrium parameters at 22 °C were calculated using the Liu model. Upon adsorption of RO-16, Qmax was 90.1 mg g−1 for ZnCl2-BBC and 354.8 mg g−1 for KOH-BBC. With RB-4, Qmax was 332.9 mg g−1 for ZnCl2-BBC and 582.5 mg g−1 for KOH-BBC. Based on characterization and experimental data, it was suggested that electrostatic interactions and hydrogen bonds between BBCs and RO-16 and RB-4 dyes played the most crucial role in the adsorption process. The biobased carbon materials showed high efficiency for removing RO-16 and RB-4, comparable to the best examples from the literature. Additionally, both the KOH- and ZnCl2-BBC showed a high ability to purify two synthetic effluents, but the KOH-BBC was superior.

Efficient removal of Hg2+ from aqueous solution by a novel composite of nano humboldtine decorated almandine (NHDA): Ion exchange, reducing-oxidation and adsorption

Efficient removal of Hg²⁺ from aqueous solution is key for environmental protection and human health. Herein, a novel composite of nano humboldtine decorated almandine was synthesized from almandine for the removal of Hg²⁺. Results showed that the Hg²⁺ removal process followed pseudo-second-order kinetic model and Langmuir equation, and the maximum adsorption capacity was 575.17 mg/g. Furthermore, Hg²⁺ removal by the composite was pH-dependent and low pH value facilitated the removal of Hg²⁺. SEM and HADDF-STEM results suggested a new rod morphology was generated and the adsorbed mercury was mainly enriched into this structure after reaction with Hg²⁺ solution. The removal mechanisms of Hg²⁺ by the composite was pH dependent, and included ion exchange, surface complexation, reduction and oxidation. Our results demonstrated that the composite was an ideal material for Hg²⁺ removal and the transformation ways of mercury related species could be a significant but currently underestimated pathway in natural and engineered systems.

Evaluation of CNT-COOH/MnO2/Fe3O4 nanocomposite for ibuprofen and paracetamol removal from aqueous solutions

The nanocomposite CNT-COOH/MnO₂/Fe₃O₄ was synthesized and characterized by different techniques, namely X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetric analysis, Brunauer-Emmett-Teller analysis, magnetic measurement, point of zero charge and hydrophobicity index. Analyzes revealed the groups -COOH, MnO₂ and Fe₃O₄ attached to the carbon nanotubes, the acidic character of the obtained nanocomposite and its stability. The surface area for the obtained nanocomposite was 114.2 m² g^-1. The prepared nanocomposite was used for adsorption of ibuprofen and paracetamol from aqueous solution. Isotherm, kinetic and thermodynamic parameters were determined for predicting the ibuprofen and paracetamol adsorption on synthetized nanocomposite. The equilibrium data obtained from adsorption were well represented by Langmuir model and kinetics data were well fitted by the pseudo-second order model. The maximum adsorption capacity obtained for ibuprofen and paracetamol was 103.093 mg g^-1, 80.645 mg g^-1 respectively. The thermodynamic analysis showed that the adsorption process for both pollutants was spontaneous and endothermic. The synthetized nanocomposite can be a suitable new absorbent for ibuprofen and paracetamol removal from aqueous solutions due to its high adsorbing capacity and it can be separated by an external magnetic field.

Rapid elimination of trace bisphenol pollutants with porous β-cyclodextrin modified cellulose nanofibrous membrane in water: adsorption behavior and mechanism

A porous β-cyclodextrin modified cellulose nano-fiber membrane (CA-P-CDP) was fabricated and employed to treat the trace bisphenol pollutants (bisphenol A (BPA), bisphenol S (BPS), and bisphenol F (BPF)) in water. The characterization highlighted the porous structure, stable crystal structure, good thermal stability of the obtained CA-P-CDP, as well as abundant functional groups, which could greatly improve the adsorption of bisphenol pollutants and recovery. During the static adsorption process, the adsorbents dosage, temperature and pH showed significant influence on the adsorption performance. At the selected conditions (25 °C, 7.0 of pH and 0.1 g L^-1 of CA-P-CDP dosage), the BPA/BPS/BPF adsorption on CA-P-CDP could rapidly reached the equilibrium in 15 min by following the pseudo-second-order kinetic model, and the maximum adsorption capacities were 50.37, 48.52 and 47.25 mg g^-1, respectively, according to Liu isotherm model. The mechanisms between the bisphenol pollutants and CA-P-CDP mainly involved the synergism of hydrophobic effects, hydrogen-bonding interactions and π-π stacking interactions. Besides, the dynamic adsorption data showed that the volume of treated water for CA-P-CDP (0.58 L) was 14.5 times larger than that of pristine cellulose membrane (0.04 L), revealing satisfactory adsorption performance of trace BPA in water. Furthermore, during the treatment of real water samples (lake water and river water) with trace bisphenol pollutants, the complete removal of the pollutants were evidently observed, which strongly verified the possibility of CA-P-CDP for the practical application.

Radioactive cesium ion removal from wastewater using polymer metal oxide composites

Radioactive cesium ion (Cs-137) removal from wastewater was investigated by novel composite adsorbents, chitosan-bone powder (CS-KT) and chitosan-bone powder-iron oxide (CS-KT-M) at 25 and 50 °C. The characterization of adsorbents was performed by Fourier-Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Brunauer-Emmett-Teller and Barrett-Joyner-Hallenda (BET-BJH), and Atomic Force Microscopy (AFM) analyses. While BET surface areas of CS-KT and CS-KT-M adsorbents were found to be 131.5 and 144.9 m²/g, respectively, average pore size and pore volume values were 4.69 nm/0.154 cm³/g and 7.49 nm/0.271 cm³/g, respectively. Amongst Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) models, Langmuir model fits well for Cs⁺ ion sorption by these adsorbents. The maximum adsorption capacity obtained from Langmuir adsorption isotherm was 0.98 × 10^-4 mol/g at 25 °C, and 1.16 × 10^-4 mol/g at 50 °C for CS-KT; it was found to be 1.79 × 10^-4 mol/g at 25 °C and 2.24 × 10^-4 mol/g at 50 °C for CS-KT-M. FT-IR analyses showed that Cs⁺ sorption occurs by its interaction with CO₃^2-, PO₄^3- and -NH₂ groups. The average adsorption energy "E" was calculated as ca.11 kJ/mol from D-R adsorption isotherm. The adsorption kinetics was interpreted well by pseudo-second order model.

Adsorption of ibuprofen, ketoprofen, and paracetamol onto activated carbon prepared from effluent treatment plant sludge of the beverage industry

The presence of emerging contaminants such as pharmaceuticals in aquatic means presents as a serious threat, since their real consequences for the environment and human health are not well known. Therefore, this work consisted of preparing and characterize sludge-derived activated carbons (beverage sludge activated carbon - BSAC and acid-treated beverage sludge activated carbon - ABSAC) to investigate their use in the pharmaceuticals adsorption in aqueous media. The morphology study has demonstrated that ABSAC, unlike BSAC, exhibited an abundant porous structure, with smaller particles and bigger roughness. Adsorption results indicated that the ABSAC was more effective that BSAC, since it presented superior surface area (642 m² g^-1) and total pore volume (0.485 cm³ g^-1) values. Pseudo-second-order kinetic model was more suitable to predict experimental data. Sips model best described the equilibrium data, with maximum adsorption capacities of 145, 105, and 57 mg g^-1 for paracetamol, ibuprofen, and ketoprofen, respectively. Besides, the sludge-derived adsorbent was highly efficient in the treatment of a simulated drug effluent, removing 85.16% of the pharmaceutical compounds. Therefore, the material prepared in this work possesses intrinsic characteristics that make it a remarkable adsorbent to be applied in the treatment of pharmaceutical contaminants contained in industrial wastewater.

Removal of aqueous Cr(VI) by magnetic biochar derived from bagasse

We prepared a novel adsorbent functionalized by bagasse magnetic biochar (BMBC). To study the removal behaviors and mechanisms of Cr(VI) by BMBC, batch adsorption experiments were conducted by modifying variables, such as pH, adsorption time, BMBC dosages, initial Cr concentration, co-existing ions, and ionic strength, and characterizing BMBC before and after Cr(VI) adsorption. BMBC was primarily composed of Fe₂O₃ and Fe₃O₄ on bagasse boichar with an amorphous structure. The specific surface area of BMBC was 81.94 m² g⁻¹, and the pH_pzc of BMBC was 6.2. The fabricated BMBC showed high adsorption performance of Cr(VI) in aqueous solution. The maximum Cr(VI) adsorption capacity of BMBC was 29.08 mg g⁻¹ at 25 ºC, which was much higher than that of conventional biochar sorbents. The adsorption process followed pseudo-second-order kinetics and could be explained by the involvement of the Langmuir isotherm in monolayer adsorption. The crystalline structure of Fe₃O₄ in the BMBC changed slightly during the adsorption process; Fe₃O₄ improved the adsorption of Cr(VI) on BMB. The desorption capacity of Cr(VI) was 8.21 mg g⁻¹ when 0.2 mol L⁻¹ NaOH was used as the desorption solution. After being reused three times, the removal efficiency is still as high as 80.36%.

Ultrafast removal of radioactive strontium ions from contaminated water by nanostructured layered sodium vanadosilicate with high adsorption capacity and selectivity

Layered sodium vanadosilicates was synthesized for removing soluble strontium ion (Sr²⁺) from simulated radioactive wastewater. SEM, EDS and TEM images indicated that layered sodium vanadosilicates had a nanostructure with flake-like shape providing an extremely large surface area. XRD, FTIR and XPS analyses further revealed a framework structure of adsorbent consisting of corner-sharing SiO₄ tetrahedra and VO₆ octahedra, with sodium ion being the major cation in the synthesized nanostructured layered sodium vanadosilicate. This study for the first time showed ultrafast adsorption of Sr²⁺ by nanostructured layered sodium vanadosilicates in a time frame of seconds with a high adsorption capacity of 174.3 mg/g estimated from Langmuir isotherm. It was found that about 99.0% of Sr²⁺ at an initial concentration of 5.00 mg/L and adsorbent dosage of 0.5 g/L could be removed within several seconds. The kinetic analysis further revealed that pseudo-second-order instead of pseudo-first-order kinetics could satisfactorily describe the observed ultrafast removal of Sr²⁺. In particular, the nanostructure layered sodium vanadosilicates exhibited an excellent affinity to Sr²⁺ over a wide pH range of 3-11. It was also demonstrated that the working mechanisms of nanostructured layered sodium vanadosilicates for Sr²⁺ removal mainly included surface electrostatic interaction and ion-exchange with sodium ion. Furthermore, nanostructure layered sodium vanadosilicates had significant advantages for Sr²⁺ removal compared with other adsorbents. Consequently, it is reasonable to expect that nanostructured layered sodium vanadosilicates synthesized in this study could be considered as a promising adsorbent for ultrafast and high-efficiency removal of radioactive Sr²⁺ from radioactive wastewaters.

Adsorption of 2-nitrophenol using rice straw and rice husks hydrolyzed by subcritical water

The potential of rice husks and straw as adsorbents after being processed by subcritical water hydrolysis (SWH) was investigated. The influences of temperature (453, 493 and 533 K) and liquid/solid ratio (7.5 and 15 g water/g biomass) on the rice straw and rice husks characteristics and on the adsorption capacity of 2-nitrophenol were evaluated at pH 4 and 7. Adsorption kinetics, equilibrium and thermodynamic parameters were also studied. The adsorption capacity was favored at pH 7. Pseudo-first-order model was suitable to predict the kinetic curves for 2-nitrophenol concentrations of 25, 50, 75 and 100 mg/L and the isotherm data obeyed the Freundlich model. Overall, the thermodynamic results revealed a spontaneous and exothermic process. The maximum adsorption capacity (92.97 ± 1.31 mg/g) was obtained for rice straw that has undergone an SWH at 453 K and 7.5 g water/g straw. The integration of processes to valorize co-products can make the production of cellulosic bioethanol more feasible.

Enhanced catalytic degradation of amoxicillin with TiO2-Fe3O4 composites via a submerged magnetic separation membrane photocatalytic reactor (SMSMPR)

A novel photo-Fenton catalytic system for the removal of organic pollutants was presented, including the use of photo-Fenton process and a submerged magnetic separation membrane photocatalytic reactor (SMSMPR). We synthesized TiO₂–Fe₃O₄ composites as the photocatalyst and made full use of the magnetism of the photocatalyst to realize the recollection of the catalyst from the medium, which is critical to the commercialization of photocatalytic technology for wastewater treatment. The photo-Fenton performance of TiO₂–Fe₃O₄ is evaluated with amoxicillin trihydrate (AMX) as a target pollutant. The results indicate that the TiO₂–Fe₃O₄/H₂O₂ oxidation system shows efficient degradation of AMX. Fe₃O₄ could not only enhance the heterogeneous Fenton degradation of organic compounds but also allow the photocatalyst to be magnetically separated from treated water. After four reaction cycles, the TiO₂–Fe₃O₄ composites still exhibit 85.2% removal efficiency of AMX and show excellent recovery properties. Accordingly, the SMSMPR with the TiO₂–Fe₃O₄ composite is a promising way for removing organic pollutants.

With a TiO₂–Fe₃O₄ composite as the catalyst, amoxicillin was degraded via a photo-Fenton process using a submerged magnetic separation membrane photocatalytic reactor.

Kinetic, equilibrium, and thermodynamic studies on the adsorption of ciprofloxacin by activated carbon produced from Jerivá (Syagrus romanzoffiana)

High specific surface area activated carbon prepared from endocarp of Jerivá (Syagrus romanzoffiana) (ACJ) was used for ciprofloxacin (CIP) antibiotic removal from aqueous effluents. The activated carbon (AC) was characterized via scanning electron microscope, Fourier transform infrared spectroscopy, N₂ adsorption/desorption, and pH value at the zero-charge point. Avrami kinetic model was the one that best fit the experimental results in comparison to the pseudo-first-order and pseudo-second-order kinetic models. The equilibrium data obeyed the Liu isotherm equation, showing a maximum adsorption capacity of 335.8 mg g^-1 at 40 °C. The calculated thermodynamic parameters indicate that the adsorption of CIP was spontaneous and endothermic at all studied temperatures. Also, the free enthalpy changes (∆H° = 3.34 kJ mol^-1) suggested physical adsorption between CIP and ACJ. Simulated effluents were utilized to check the potential of the ACJ for wastewater purification. The highly efficient features enable the activated carbon prepared from endocarp of Jerivá, an attractive carbon adsorbent, to remove ciprofloxacin from wastewaters.