Synthesis of magnetic activated carbon/α-Fe2O3 nanocomposite and its application in the removal of acid yellow 17 dye from water

Environmental remediation and sustainable design of iron oxide nanoparticles for removal of petroleum-derived pollutants from water: A critical review

The global problem of major oil spills not only generates crude oil pollution, but produces many derivatives that pose ecological and human health challenges. While extensive research has focused on understanding the types of these contaminants, their transport modes, detection techniques, and ecotoxicological impacts, there are still significant research gaps in mechanisms for removal of petroleum-derived pollutants by iron oxide nanoparticles (IONPs). This work summarizes systematically the types and green synthesis of IONPs for the environmental remediation of various petroleum contaminants. We also provide comprehensive coverage of the excellent removal capacity and latest environmental remediation of IONPs-based materials (e.g., pristine, modified, or porous-supported IONPs materials) for the removal of petroleum-derived pollutants, potential interaction mechanisms (e.g., adsorption, photocatalytic oxidation, and synergistic biodegradation). A sustainable framework was highlighted in depth based on a careful assessment of the environmental impacts, associated hazards, and economic viability. Finally, the review provides an possible improvements of IONPs for petroleum-derived pollutants remediation and sustainable design on future prospect. In the current global environment of pollution reduction and carbon reduction, this information is very important for researchers to synthesize and screen suitable IONPs for the control and eradication of future petroleum-based pollutants with low environmental impact.

High adsorption to methylene blue based on Fe3O4-N-banana-peel biomass charcoal

This research focused on utilizing banana peel as the primary material for producing mesoporous biomass charcoal through one-step potassium hydroxide activation. Subsequently, the biomass charcoal underwent high-temperature calcination with varying impregnation ratios of KOH : BC for different durations in tubular furnaces set at different temperatures. The resultant biomass charcoal was then subjected to hydrothermal treatment with FeCl3·6H2O to produce biochar/iron oxide composites. The adsorption capabilities of these composites towards methylene blue (MB) were examined under various conditions, including pH (ranging from 3 to 12), temperature variations, and initial MB concentrations (ranging from 50 to 400 mg L-1). The adsorption behavior aligned with the Langmuir model and demonstrated quasi-secondary kinetics. After five adsorption cycles, the capacity decreased from 618.64 mg g-1 to 497.18 mg g-1, indicating considerable stability. Notably, Fe3O4-N-BC exhibited exceptional MB adsorption performance.

Adsorption and photocatalytic degradation of 2,4-dicholrophenol using surgical mask derived SMAC-Fe2O3 composite; adsorption isotherms, kinetics, thermodynamics

Hybrid material of surgical mask activated carbon (SMAC) and Fe2O3 (SMAC-Fe2O3) composite was prepared by simple co-precipitation method and used as potential material for the remediation of 2,4-dicholrophenol (2,4-DCP). The XRD patterns exhibited the presence of SMAC and Fe2O3, FTIR spectrum showed the FeO-carbon stretching at the wavenumber from 400 to 550 cm-1. UV-Vis DRS results showed the band gap was 1.97 eV and 2.05 eV for SMAC-Fe2O3 and Fe2O3, respectively. The SEM images revealed that the Fe2O3 doped onto the fiber morphology of SMAC. The outcomes of the BET examination exhibited a surface area of 195 m2/g and a pore volume of 0.2062 cm3/g for the SMAC/Fe2O3 composite. The batch mode study shows the maximum adsorption and photocatalytic degradation efficacies which were 97% and 78%, respectively. The experimental data was studied with both linear and nonlinear adsorption isotherm and kinetics models. The nonlinear Langmuir isotherm and pseudo-second-order kinetics (PSOK) models have well fit compared with other models. The Langmuir maximum adsorption capacity (qmax) was found 161.60 mg/g. Thermodynamic analysis shows that the 2,4-DCP adsorption onto SMAC-Fe2O3 was a spontaneous and exothermic process. The PSOK assumes that the adsorption process was chemisorption. The photocatalytic degradation rate constant of 2,4-DCP was calculated using pseudo-first-order kinetics (PFOK) and the rate constant for SMAC-Fe2O3 and Fe2O3 were 0.859 × 10-2 min-1 and 0.616 × 10-2 min-1, correspondingly. In addition, the obtained composite exhibited good reusability after a few cycles. These results confirmed that SMAC-Fe2O3 composite is an effective adsorbent and photocatalyst for removing 2,4-DCP pollutants.

Photocatalytic Degradation of Antibiotics via Exploitation of a Magnetic Nanocomposite: A Green Nanotechnology Approach toward Drug-Contaminated Wastewater Reclamation

In the quest for eco-conscious innovations, this research was designed for the sustainable synthesis of magnetite (Fe3O4) nanoparticles, using ferric chloride hexahydrate salt as a precursor and extract of Eucalyptus globulus leaves as both a reducing and capping agent, which are innovatively applied as a photocatalyst for the photocatalytic degradation of antibiotics "ciprofloxacin and amoxicillin". Sugar cane bagasse biomass, sugar cane bagasse pyrolyzed biochar, and magnetite/sugar cane bagasse biochar nanocomposite were also synthesized via environmentally friendly organized approaches. The optimum conditions for the degradation of ciprofloxacin and amoxicillin were found to be pH 6 for ciprofloxacin and 5 for amoxicillin, dosage of the photocatalyst (0.12 g), concentration (100 mg/L), and irradiation time (240 min). The maximum efficiencies of percentage degradation for ciprofloxacin and amoxicillin were found to be (73.51%) > (63.73%) > (54.57%) and (74.07%) > (61.55%) > (50.66%) for magnetic nanocomposites, biochar, and magnetic nanoparticles, respectively. All catalysts demonstrated favorable performance; however, the "magnetite/SCB biochar" nanocomposite exhibited the most promising results among the various catalysts employed in the photocatalytic degradation of antibiotics. Kinetic studies for the degradation of antibiotics were also performed, and notably, the pseudo-first-order chemical reaction showed the best results for the degradation of antibiotics. Through a comprehensive and comparative analysis of three unique photocatalysts, this research identified optimal conditions for efficient treatment of drug-contaminated wastewater, thus amplifying the practical significance of the findings. The recycling of magnetic nanoparticles through magnetic separation, coupled with their functional modification for integration into composite materials, holds significant application potential in the degradation of antibiotics.

Metal Oxide-Impregnated Biochar for Azo Dye Remediation as Revealed through Kinetics, Thermodynamics, and Response Surface Methodology

This study reports for the first time the adsorption capacity of a novel adsorbent Croton bonplandianus Baill. biochar. Its adsorption capacity was further enhanced by loading magnetic composites on it, which makes it an efficient medium for the adsorption of dyes. Two azo dyes, Basic Brown 1 (BB1) and Basic Orange 2 (BO2), were studied for their effective adsorption from aqueous media. A comprehensive characterization was performed by using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) to study the properties of Fe2O3-loaded C. bonplandianus Baill. biochar (FO-CBPBB). A series of batch experiments were conducted to optimize various parameters (pH, contact time, adsorbent amount, initial BB1 and BO2 concentrations, and temperature) for the maximum adsorption of BB1 and BO2 on the FO-CBPBB adsorbent. The percentage of BB1 and BO2 dyes that adsorb to FO-CBPBB under the best experimental circumstances (pH of solution 7, contact time 80 min, temperature of solution 40 °C, initial BB1 and BO2 dye concentrations 80 mg L-1, and adsorbent dose 1 g L-1) was 93 and 95%, respectively. The best adsorption of BB1 and BO2 was accomplished by optimizing the effects of several factors, including the starting dye concentration, contact time, and temperature, based on the central composite design. The Freundlich and Langmuir isotherm models were used to examine the equilibrium data. The Langmuir isotherm with the greatest adsorption capacity and R2 value effectively captured the experimental results. When kinetic parameters were investigated, it was found that pseudo-second-order was appropriate, reflecting the fact that the dye-adsorbent interaction was the rate-controlling factor in this study. The sorption process was endothermic and spontaneous, as shown by the thermodynamic variables. Based on the interaction between the adsorbent and azo dyes, it was concluded that the adsorption process was electrostatic in nature. Adsorbents that have been synthesized can effectively remove azo dyes from wastewater. Excellent regeneration efficiency was exhibited by FO-CBPBB, which makes it an eco-friendly and cost-effective alternative to other costly techniques applied for water purification.

Synthesis and characterization of iron oxide-commercial activated carbon nanocomposite for removal of hexavalent chromium (Cr6+) ions and Mordant Violet 40 (MV40) dye

Iron Oxide-commercial activated carbon nanocomposite (CAC-IO) was prepared from commercial activated carbon (CAC) by the co-precipitation method, and the resulting nanocomposite was used as an adsorbent to remove hexavalent chromium (Cr6+) ions and Mordant Violet 40 (MV40) dye from wastewater. The produced materials (CAC, CAC after oxidation, and CAC-IO) were comparatively characterized using FTIR, BET, SEM, EDX TEM, VSM, and XRD techniques. The adsorption mechanism of Cr6+ ions and MV40 dye on CAC-IO was examined using Langmuir and Freundlich isotherm models.. Different models were applied to know the adsorption mechanism and it was obtained that Pseudo-second order fits the experimental data better. This means that the adsorption of the adsorbate on the nanocomposite was chemisorption. The maximum removal percent of Cr6+ ions by CAC-IO nanocomposite was 98.6% determined as 2 g L-1 adsorbent concentration, 100 mg L-1 initial pollutant concentration, solution pH = 1.6, the contact time was 3 h and the temperature was room temperature. The maximum removal percentage of Mordant Violet 40 dye (C.I. 14,745) from its solutions by CAC-IO nanocomposite was 99.92% in 100 mg L-1 of initial dye concentrations, 1.0 g L-1 of adsorbent concentration, solution pH = 2.07, the contact time was 3 h. The MV40 dye adsorption on CAC-IO was the most fitted to the Freundlich isotherm model. The maximum adsorption capacity was calculated according to the Langmuir model as 833.3 mg g-1 at 2 g L-1 of adsorbent concentration and 400 mg L-1 of initial MV40 dye concentration. The Cr6+ ions adsorption on CAC-IO was more fitted to the Freundlich model with Qmax, equal to 312.50 mg g-1 at 1 g L-1 adsorbent concentration and 400 mg L-1 of Cr6+ ions initial concentrations.

Orange peel magnetic activated carbon for removal of acid orange 7 dye from water

Magnetic activated carbon resources with a remarkably high specific surface area have been successfully synthesized using orange peels as the precursor and ZnCl2 as the activating agent. The impregnation ratio was set at 0.5, while the pyrolysis temperature spanned from 700 to 900 °C. This comprehensive study delved into the influence of activation temperatures on the resultant pore morphology and specific surface area. Optimal conditions were discerned, leading to a magnetic activated carbon material exhibiting an impressive specific surface area at 700 °C. The Brunauer-Emmett-Teller surface area reached 155.09 m2/g, accompanied by a total pore volume of 0.1768 cm3/g, and a mean pore diameter of 4.5604 nm. The material displayed noteworthy properties, with saturation magnetization (Ms) reaching 17.28 emu/g, remanence (Mr) at 0.29 emu/g, and coercivity (Hc) of 13.71 G. Additionally, the composite demonstrated super-paramagnetic behaviour at room temperature, facilitating its rapid collection within 5 s through an external magnetic field. Factors such as absorbent dose, initial concentration of the adsorbate, contact time, and pH were systematically examined. The adsorption behaviour for acid orange 7 (AO7) was found to adhere to the Temkin isotherm models (R2 = 0.997). The Langmuir isotherm model suggested a monolayer adsorption, and the calculated maximum monolayer capacity (Qm) was 357.14 mg/g, derived from the linear solvation of the Langmuir model using 0.75 g/L as an adsorbent dose and 150-500 mg/L as AO7 dye concentrations. The pseudo-second order model proved to be the best fit for the experimental data of AO7 dye adsorption, with a high coefficient of determination (R2) ranging from 0.999 to 1.000, outperforming other kinetic models.

Sequestration of chromium(vi) and nickel(ii) heavy metals from unhygienic water via sustainable and innovative magnetic nanotechnology

In a stride towards sustainable solutions, this research endeavors to address the critical issue of water pollution via heavy metals by coupling the power of magnetic nanotechnology, in combination with a green chemistry approach, to eliminate two noxious inorganic pollutants: chromium(vi) and nickel(ii) from aqueous environments. The synthesis of magnetite (Fe3O4) nanoparticles was achieved using ferric chloride hexahydrate (FeCl3·6H2O) as a precursor, with the assistance of Ziziphus mauritiana Lam. leaves extract, known for its remarkable salt-reducing properties. A range of bio-adsorbents, derived from corncob biomass, corncob pyrolyzed biochar, and magnetite/corncob biochar nanocomposite (NC), were engineered for their eco-friendly and biocompatible characteristics. Extensive parametric optimizations, including variations in pH, contact time, dose rate, and concentration, were carried out to gain insights into the adsorption behavior and capacity of these bioadsorbents concerning Cr(vi) and Ni(ii). Equilibrium and kinetic studies were undertaken to comprehensively understand the adsorption dynamics. In the case of Ni(ii), the Freundlich isotherm model provided a satisfactory fit for all bio-adsorbents, demonstrating R2 values of 0.91, 0.95, and 0.96 for BM, BC, and NC, respectively. Furthermore, the pseudo 1st order model emerged as the most suitable fit for Cr(vi) sequestration in corncob BM with an R2 value of 0.98, while pseudo 2nd order models were robustly fitted for BC and NC, yielding R2 values of 0.88 and 0.99, respectively. The magnetite/corncob nanocomposite outperformed other bioadsorbents in removing heavy metals from wastewater due to its environmental friendliness, larger surface area, reusability, and cost-effectiveness at an industrial scale.

Removal of Cr6+ ions and mordant violet 40 dye from liquid media using Pterocladia capillacea red algae derived activated carbon-iron oxides

In recent years, water pollution has become one of the most dangerous problems facing the world. Pollution of water with heavy metals and different dyes has caused many harmful effects on human health, living organisms and our environment. In this study, iron oxide nanomagnetic composite from Pterocladia Capillacea red algae-derived activated carbon (PCAC-IO) was synthesized by co-precipitation method using different iron salts and different base solutions. The synthesized nanocomposite was investigated with various characterization techniques such as FTIR, BET, SEM-EDX, TEM, XRD, and VSM. The obtained PCAC-IO adsorbent was used for Cr6+ ions and Mordant Violet 40 (MV40) dye removal. The adsorption mechanism of Cr6+ ions and MV40 dye on PCAC-IO was examined using several adsorption and kinetic isotherm models. Langmuir and Freundlich models were investigated using experimental data. Pseudo-first-order (PFO), Pseudo-second-order (PSO) and intraparticle diffusion models (IPDM) were applied to identify the adsorption mechanism. It has shown that the PSO kinetic model fits better with the experimental data obtained from PCAC-IO. This result can be interpreted as the adsorption of the adsorbate on the nanocomposite as chemical adsorption. The optimum conditions for maximum Cr6+ ions removal (96.88%) with PCAC-IO adsorbent occur at room temperature, 5 g L-1 adsorbent concentration, 100 mg L-1 initial pollutant concentration, pH 1 and at the end of 180 min, while maximum MV40 dye removal (99.76%), other conditions being the same, unlikely it occurred at pH 2.06 and after 45 min. The most suitable model for Cr6+ ions removal under the conditions of 1 L-1 g adsorbent concentration and 400 mg L-1 adsorbate concentration was Langmuir (Qmax = 151.52 mg g-1), while for MV40 removal it was Freundlich (Qmax = 303.03 mg g-1). We propose the use of activated carbon-supported iron oxide prepared from bio-waste material, especially from Pterocladia Capillacea red algae, as a promising adsorbent with high efficiency in the removal of Cr6+ ions and MV40 dye from aqueous media.

Response surface methodology, and artificial neural network model for removal of textile dye Reactive Yellow 105 from wastewater using Zeolitic Imidazolate-67 modified by Fe3O4 nanoparticles

The applicability of Zeolitic Imidazolate-67, Modified by Fe3O4 Nanoparticles, was studied for removing textile dye Reactive yellow 105 from wastewater by adsorption method using response surface methodology (RSM). For the adsorption characterization of the adsorbent used in HE-4G dye adsorption, BET, FTIR, XRD, and SEM analyses were performed. The impacts of variables, including initial HE-4G dye concentration (X1), pH (X2), adsorbent dosage (X3), and sonication time (X4), the highest removal efficiency as 98%, 10 mg/L initial concentration, pH 6, 0.025 g adsorbent dosage, and 6.0 min time respectively. Adsorption equilibrium and kinetic data it, that data were for the Langmuir isotherm, pseudo-second-order kinetics, and maximum adsorption capacity (105.0 mg/g), respectively. Thermodynamic parameters indicated HE-4G dye adsorption is feasible, spontaneous and exothermic. Promising treatment capabilities of the ZIF-67-Fe3O4NPs have been during the comparative adsorption removal of HE-4G dye from DI water against spiked natural water samples and synthetic Na+, K+, Ca2+, and Mg2+ solutions. The observed outcome is the suitability of the artificial neural network model as a tool for mean square error, (MSEANN = 0.53, and R2 = 0.9926) for removing HE-4G dye. Results that ZIF-67-Fe3O4NPs, like being recyclable, and cost-efficient made it a promising absorbent for wastewater.

Immunomagnetic Isolation of HER2-Positive Breast Cancer Cells Using a Microfluidic Device

Analysis of circulating tumor cells (CTCs) as a tool for monitoring metastatic cancers, early diagnosis, and evaluation of disease prognosis paves the way toward personalized cancer treatment. Developing an effective, feasible, and low-cost method to facilitate CTC isolation is, therefore, vital. In the present study, we integrated magnetic nanoparticles (MNPs) with microfluidics and used them for the isolation of HER2-positive breast cancer cells. Iron oxide MNPs were synthesized and functionalized with the anti-HER2 antibody. The chemical conjugation was verified by Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and dynamic light scattering/zeta potential analysis. The specificity of the functionalized NPs for the separation of HER2-positive from HER2-negative cells was demonstrated in an off-chip test setting. The off-chip isolation efficiency was 59.38%. The efficiency of SK-BR-3 cell isolation using a microfluidic chip with a S-shaped microchannel was considerably enhanced to 96% (a flow rate of 0.5 mL/h) without chip clogging. Besides, the analysis time for the on-chip cell separation was 50% faster. The clear advantages of the present microfluidic system offer a competitive solution in clinical applications.

Orange peels magnetic activate carbon (MG-OPAC) composite formation for toxic chromium absorption from wastewater

This work prepared a composite of orange peels magnetic activated carbon (MG-OPAC). The prepared composite was categorized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), Energy-dispersive X-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM) and vibrating-sample magnetometer (VSM) analyses. The MG-OPAC composite showed the surface area (155.09 m²/g), the total volume of pores (0.1768 cm³/g), and the mean diameter of pores (4.5604 nm). The saturation magnetization (Ms = 17.283 emu/g), remanence (Mr = 0.28999 emu/g) and coercivity (Hc = 13.714 G) were reported for the prepared MG-OPAC. Likewise, at room temperature, the MG-OPAC was in a super-paramagnetic state, which could be collected within 5 S (< 5 S) with an outside magnetic field. Influence of time of contact, absorbent dose, starting concentration of Cr⁶⁺ ions, and pH were tested to adjust the absorption process. The absorption behavior of MG-OPAC for hexavalent chromium was investigated by Langmuir (LIM), Freundlich (FIM) and Temkin (TIM) isotherm models (IMs). Applicability of LIM specifies that Cr⁶⁺ ions absorption procedure may be monolayer absorption. The maximum monolayer capacity (Q_m) premeditated by LIM was 277.8 mg/g. Similarly, the absorption process was tested with different kinetic models like intraparticle diffusion (IPDM), pseudo-first-order (PFOM), Elovich (EM), pseudo-second-order (PSOM), and Film diffusion (FDM). The PSOM was best fitted to the experimental results of Cr⁶⁺ ions absorption with R² ranging between 0.992 and 1.

Magnetic activated carbon synthesized using rubber fig tree leaves for adsorptive removal of tetracycline from aqueous solutions

The current study emphasizes the activated carbon fabrication from rubber fig leaves, the establishment of its composite with iron oxide nanoparticles (RFAC@Fe₂O₃), and its relevance in the adsorptive elimination of tetracycline. The physical and functional properties of RFAC@Fe₂O₃ nanocomposite were uncovered by multiple approaches. Elemental analysis portrayed the existence of carbon, oxygen, and iron, while FESEM analysis revealed that Fe₂O₃ nanoparticle agglomerates were entrenched in the activated carbon matrix rendering it a rough abrasive texture. FT-IR analysis reported the presence of functional groups attributing to CC, -OH, crystalline iron oxide, and Fe-O stretching vibrations, and XRD corroborated graphitic crystalline structure, oxygenated functional groups attached to carbon accompanied by crystalline plane corresponding to Fe₂O₃ nanoparticles. XPS spectra depicted signature peaks for C, O, and Fe, while VSM studies designated its superparamagnetic nature. The high surface area (662.73 m²/g), pore size (3.12 nm), and mesoporous nature of RFAC@Fe₂O₃ make it apt for the adsorption of pollutants from contaminated samples. The adsorption of tetracycline (50 ppm) by RFAC@Fe₂O₃ was maximum at pH 4.0. As the nanocomposite dosage and stirring speed increased to 2.0 g/L and 150 rpm, maximum adsorption was observed due to more active binding sites and improved mixing. Freundlich isotherm along with pseudo-second-order model well described adsorption process divulging that tetracycline was adsorbed onto RFAC@Fe₂O₃ composite in multi-layers by chemisorption. Thermodynamic analysis signified negative values for ΔG°, while positive values for ΔH° and ΔS were obtained, indicating spontaneous feasible endothermic adsorption.

Adsorptive removal of tetracycline from aqueous solutions using magnetic Fe2O3 / activated carbon prepared from Cynometra ramiflora fruit waste

Herein, the sustainable fabrication of magnetic iron oxide nanoadsorbent prepared with activated carbon of inedible Cynometra ramiflora fruit has been investigated. Activated carbon was obtained from phosphoric acid-treated C. ramiflora fruit, which was then utilized for the synthesis of magnetic nanocomposite (CRAC@Fe₂O₃). The formed nanocomposite was a porous irregular dense matrix of amorphous evenly sized spherical nanoparticles, as visualized by FESEM, and also contained carbon, oxygen, iron, and phosphorous in its elemental composition. FT-IR spectrum depicted characteristic bands attributing to Fe-O, C-OH, C-N, CC, and -OH bonds. VSM and XRD results proved that CRAC@Fe₂O₃ was superparamagnetic with a moderate degree of crystallinity and high saturation magnetization value (1.66 emu/g). Superior surface area, pore size, and pore volume of 766.75 m²/g, 2.11 nm, and 0.4050 cm³/g respectively were measured on BET analysis of CRAC@Fe₂O₃ nanocomposite, indicating their suitability for use as an adsorbent. On application of this nanocomposite for adsorption of tetracycline, maximum removal of 95.78% of 50 ppm TC at pH 4, CRAC@Fe₂O₃ 0.4 g/L in 240 min. The adsorption of TC by CRAC@Fe₂O₃ was confirmed as monolayer sorption by ionic interaction (R² = 0.9999) as it followed pseudo-second-order kinetics and Langmuir isotherm (R² = 0.9801). CRAC@Fe₂O₃ showed a maximum adsorption capacity of 312.5 mg/g towards TC antibiotics indicating its potential for the treatment of antibiotic-contaminated samples. Since negative ΔG^o and positive ΔH^o and ΔS^o values were obtained at all tested temperatures during the thermodynamic studies, the adsorption was confirmed to be endothermic, spontaneous, and feasible with an enhanced degree of randomness.

Bio-Inspired Synthesis of Carbon-Based Nanomaterials and Their Potential Environmental Applications: A State-of-the-Art Review

Providing safe drinking water and clean water is becoming a more challenging task all around the world. Although some critical issues and limits remain unsolved, implementing ecologically sustainable nanomaterials (NMs) with unique features, e.g., highly efficient and selective, earth-abundance, renewability, low-cost manufacturing procedures, and stability, has become a priority. Carbon nanoparticles (NPs) offer tremendous promise in the sectors of energy and the environment. However, a series of far more ecologically friendly synthesis techniques based on natural, renewable, and less expensive waste resources must be explored. This will reduce greenhouse gas emissions and harmful material extraction and assist the development of green technologies. The progress achieved in the previous 10 years in the fabrication of novel carbon-based NMs utilizing waste materials as well as natural precursors is reviewed in this article. Research on carbon-based NPs and their production using naturally occurring precursors and waste materials focuses on this review research. Water treatment and purification using carbon NMs, notably for industrial and pharmaceutical wastes, has shown significant potential. Research in this area focuses on enhanced carbonaceous NMs, methods, and novel nano-sorbents for wastewater, drinking water, groundwater treatment, as well as ionic metal removal from aqueous environments. Discussed are the latest developments and challenges in environmentally friendly carbon and graphene quantum dot NMs.

Towards deep purification of secondary textile effluent by using a dynamic membrane process: Pilot-scale verification

The present investigation used regular powered activated carbon (PAC) as the dynamic membrane (DM) material and successfully built-up a pilot-scale DM system for deep purification of the secondary textile effluent, which aimed at verifying the technical and economic feasibility of the DM with real secondary textile effluent. The hydrodynamic experiments indicated that the filtration resistance gradually increased along with the operation of DM system, and among which, the PAC size was the most important influencing factor. More dosage and smaller sized PAC were beneficial to enhance the purification effect of micro-organic pollutants, but they simultaneously improved the operational costs, which implied that the adoption of DM materials should comprehensively consider the removal results and the type and dosage of DM materials for obtaining an optimal result, and the operational costs would be drastically reduced by regenerating the wasted PAC. More than 50% residual micro-organic pollutants were further removed by the system, and they were mainly some aliphatic and aromatic compounds, which were the main refractory organic pollutants in most textile effluents. It was also proved by the pilot-scale DM study that the removed residual pollutants from the secondary textile effluent were mainly aromatic protein II. Due to the contained complex functional groups in their molecular structure, soluble microbial metabolites were relatively easier to be removed by the DM layer.

Nano-sized hematite-assembled carbon spheres for effectively adsorbing paracetamol in water: Important role of iron

This study developed a new α-Fe2O3 (hematite) nanoparticles-loaded spherical biochar (H-SB) through the direct pyrolysis of glucose-derived spherical hydrochar and FeCl3. The optimal impregnation ratio (hydrochar and FeCl3) was 1/1.25 (wt/wt). H-SB was applied to remove paracetamol (PRC) from water. Results indicated that H-SB exhibited a relatively low surface area (127 m2/g) and total pore volume (0.089 cm3/g). The presence of iron particles in its surface was confirmed by scanning electron microscopy with energy dispersive spectroscopy. The dominant form of iron nanoparticles (α-Fe2O3) in its surface was confirmed by X-ray powder diffraction and Raman spectrum. The crystallite size of α-Fe2O3 in H-SB was 27.4 nm. The saturation magnetization of H-SB was 6.729 cmu/g. The analysis of Fourier-transform infrared spectroscopy demonstrated that the C-O and O-H groups were mainly responsible for loading α-Fe2O3 nanoparticles in its surface. The adsorption study indicated the amount of PRC adsorbed by H-SB slightly decreased within solution pH from 2 to 11. The adsorption reached a fast saturation after 120 min. The Langmuir maximum adsorption capacity of H-SB was 49.9 mg/g at 25 °C and pH 7.0. Ion-dipole interaction and π-π interaction played an important role in adsorption mechanisms, while hydrogen bonding and pore filling were minor. Therefore, H-SB can serve as a promising material for treating PRC-contaminated water streams.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material is available in the online version of this article at 10.1007/s11814-021-1013-z.

Magnetic activated charcoal/Fe2O3 nanocomposite for the adsorptive removal of 2,4-Dichlorophenoxyacetic acid (2,4-D) from aqueous solutions: Synthesis, characterization, optimization, kinetic and isotherm studies

Magnetic activated charcoal/Fe₂O₃ nanocomposite (AC/Fe₂O₃NC) was fabricated using Spondias dulcis leaf extract by a facile method and used for the adsorptive removal of 2,4-Dichlorophenoxyacetic acid (2,4-D) from aqueous solutions for the first time. The nanocomposite was characterized by methods such as FE-SEM, EDS, XRD, FTIR, TGA, VSM, and BET to identify and confirm the surface morphology, elemental composition, crystalline nature, functional groups, thermal stability, magnetic behavior, and surface area respectively. Box-Behnken Design (BBD) - an optimization method, which belongs to the Response surface methodology (RSM) and a modeling tool - Artificial Neural Network (ANN) were employed to design, optimize and predict the relationship between the input parameters (pH, initial concentration of 2,4-D, time and agitation speed) versus the output parameter (adsorption efficiency of 2,4-D). Adsorption efficiency of 98.12% was obtained at optimum conditions (pH: 2.05, initial concentration: 32 ppm, contact time: 100 min, agitation speed: 130 rpm, temperature: 30 °C, and dosage: 0.2 g/L). The predictive ability of the ANN was superior (R² = 0.99) than the quadratic model, given by the RSM (R² = 0.93). The equilibrium data were best-fitted to Langmuir isotherm (R² = 0.9944) and the kinetics obeyed pseudo-second-order model (R² = 0.9993) satisfactorily. Thermodynamic studies revealed the spontaneity and exothermic nature of adsorption. The maximum adsorption capacity, q_m was found to be 255.10 mg/g, substantially larger than the reported values for 2,4-D adsorption by other magnetic nanoadsorbents. Therefore, this nanoadsorbent may be utilized as an excellent alternative for the elimination of 2,4-D from the waterbodies.

Flower-Like Dual-Defective Z-Scheme Heterojunction g-C3N4/ZnIn2S4 High-Efficiency Photocatalytic Hydrogen Evolution and Degradation of Mixed Pollutants

Graphitic carbon nitride (g-C₃N₄) with a porous nano-structure, nitrogen vacancies, and oxygen-doping was prepared by the calcination method. Then, it was combined with ZnIn₂S₄ nanosheets containing zinc vacancies to construct a three-dimensional (3D) flower-like Z-scheme heterojunction (pCN-N/ZIS-Z), which was used for photocatalytic hydrogen evolution and the degradation of mixed pollutants. The constructed Z-scheme heterojunction improved the efficiency of photogenerated charges separation and migration, and the large surface area and porous characteristics provided more active sites. Doping and defect engineering can change the bandgap structure to improve the utilization of visible light, and can also capture photogenerated electrons to inhibit recombination, so as to promote the use of photogenerated electron-hole pairs in the photocatalytic redox process. Heterojunction and defect engineering synergized to form a continuous and efficient conductive operation framework, which achieves the hydrogen production of pCN-N/ZIS-Z (9189.8 µmol·h^-1·g^-1) at 58.9 times that of g-C₃N₄ (155.9 µmol·h^-1·g^-1), and the degradation rates of methyl orange and metronidazole in the mixed solution were 98.7% and 92.5%, respectively. Our research provides potential ideas for constructing a green and environmentally friendly Z-scheme heterojunction catalyst based on defect engineering to address the energy crisis and environmental restoration.

Efficient removal of acetochlor pesticide from water using magnetic activated carbon: Adsorption performance, mechanism, and regeneration exploration

In this study, MnFe₂O₄ supported activated carbon magnetic adsorbent (MnFe₂O₄@AC) was successfully prepared by a simple one-pot solvothermal method and used for the adsorption and removal of acetochlor from aqueous media. Results showed that MnFe₂O₄@AC with a MnFe₂O₄/AC mass ratio of 1:2 was characterized by good magnetism and high acetochlor adsorption capacity over a wide ranging pH, ionic strength, and humic acid concentration in an aqueous solution. Acetochlor was adsorbed on MnFe₂O₄@AC mainly by hydrogen bonding, π-π interactions, and pore-filling via film, intraparticle, and pore diffusion steps. Adsorption reaction generally approached an equilibrium after 10 h, with the adsorption capacity being ca. 226 mg g^-1 for 0.2 g L^-1 adsorbent at 25 °C. Adsorbate (acetochlor) degradation and adsorbent regeneration were simultaneously achieved through heat-activated peroxymonosulfate (PMS) oxidation catalyzed by MnFe₂O₄ on the AC surface with >90% degradation efficiency at ≥9.6 mM PMS concentration at 70 °C within 12 h. However, the adsorption capacity of the regenerated adsorbent decreased by 50% of its original capacity. This needs to be addressed in future studies. MnFe₂O₄@AC adsorbent has the advantages of high adsorption capacity, good magnetism, and catalyzation, which are promising for adsorption, separation, and degradation for the effective removal and treatment of acetochlor as well as other organic contaminants in different types of waters.

Unveiling the correlation of Fe3O4 fractions upon the adsorption behavior of sulfamethoxazole on magnetic activated carbon

Magnetic particles (MPs) assisted powdered activated carbon (PAC) is a promising composite material for adsorption removal of micropollutants. The fractional amount of Fe₃O₄ impacts the balance between adsorption capacity and magnetic property of magnetic activated carbons (MPACs), and therefore it affects the extent of sulfamethoxazole (SMX) removal. Here, five MPACs with different mass ratios of Fe₃O₄: PAC (1:1, 1:2, 1:4, 1:6, and 1:8) were prepared using a hydrothermal method and characterized by various spectroscopic methods. The spherical shaped MPs were monolayerly deposited on PAC with fewer pores blocked when the mass ratio of Fe₃O₄ was comparatively low (≤ 20%). MPAC6 (14.3 wt% of Fe₃O₄) had the best overall performance, with good Langmuir adsorption capacities for SMX (173.0 mg g^-1) and excellent magnetic properties (9.0 emu g^-1). Corresponding adsorption kinetics fitted well with the pseudo second-order kinetic model. The negative ΔG⁰ (-25.6 to -27.2 KJ mol^-1) and ΔH⁰ (-9.14 KJ mol^-1), and positive ΔS⁰ (0.55 KJ mol^-1 K^-1) properties indicated the spontaneous and exothermic nature of the adsorption process accompanied by an increase in entropy. The strong cation-assisted electron donor-acceptor and hydrophobic interactions were contributed to a high extent of SMX removal in the pH range of 2-4. Formation of negative charge-assisted H-bonds was responsible for the adsorption of hydrophilic SMX^- on negatively charged MPAC6 in alkaline solution. Desorption and regeneration experiments showed SMX removal was still 92.3% in the 5th cycle. These findings give valuable insights into the interactions between SMX and MPACs and guide for choosing sustainable magnetic adsorbents for environmental applications.

Removal of anionic (Acid Yellow 17 and Amaranth) dyes using aminated avocado (Persea americana) seed powder: adsorption/desorption, kinetics, isotherms, thermodynamics, and recycling studies

Aminated avocado seed powder (AASP)-an eco-friendly novel adsorbent has been used for the removal of Acid Yellow 17 (AY 17) and Amaranth (AMR) from an aqueous phase. The AASP (before and after adsorption) was systematically characterized by different analytical techniques such as FT-IR, FESEM, EDX, and N₂ adsorption-desorption analysis. Non-linear form of various kinetic (PFO and PSO) and isotherm (Langmuir and Freundlich) models were used to examine the adsorption behavior of AY 17 and AMR onto AASP. The adsorption of AY 17 and AMR onto AASP was well illustrated by the PSO kinetic model and Langmuir isotherm models. At 303 K, the maximum adsorption capacities (obtained from the Langmuir) of the AASP for AY 17 and AMR was 42.7 and 89.2 mg/g, respectively. The AY 17 and AMR adsorption was strongly pH-dependent with an optimum pH value of 2.0. Activation energy was calculated as 12.3 and 16.3 kJ/mol for AY 17 and AMR respectively, suggesting physical adsorption. The positive values of ΔG^o and ΔH^o indicated that the adsorption process of AY 17 and AMR onto AASP was non-spontaneous and endothermic. The negligible loss of adsorption capacity and excellent regeneration of AASP were observed for the five cycles. Statement of novelty: The present research majorly focused on the synthesis of adsorbent from Avocado seed for the removal of Acid Yellow 17 and Amaranth anionic dyes from aqueous solution. Although the literature is available on direct seed powder as adsorbent, to the best of our knowledge, no chemical modified adsorbent synthesis was not available. Hence, to fill the gap in the literature, we chose the following study that significantly enhanced the adsorption efficiency of the selected anionic dyes.

Fabrication, application, optimization and working mechanism of Fe2O3 and its composites for contaminants elimination from wastewater

Fe₂O₃ and its composites have been extensively investigated and employed for the remediation of contaminated water with the characteristics of low cost, outstanding chemical stability, high efficiency of visible light utilization, excellent magnetic ability and abundant active sites for adsorption and degradation. In this review, the potentials of Fe₂O₃ in water remediation were discussed and summarized in detail. Firstly, various synthesis methods of Fe₂O₃ and its composites were reviewed and compared. Based on the structures and characteristics of the obtained materials, their applications and related mechanisms in pollutants removal were surveyed and discussed. Furthermore, several strategies for optimizing the remediation processes, including dispersion, immobilization, nano/micromotor construction and simultaneous decontamination, were also highlighted and discussed. Finally, recommendations for further work in the development of novel Fe₂O₃-related materials and its practical applications were proposed.

High-pressure Raman investigation of high index facets bounded-Fe2O3pseudocubic crystals

High index facet bounded α-Fe2O3pseudocubic crystals has gained the attention of the scientific community due to its promising electrochemical sensing response towards aqueous ammonia. The structural stability of α-Fe2O3pseudocubic crystals is investigated through high-pressure Raman spectroscopy up to 22.2 GPa, and those results are compared with ourab initiotheoretical calculations. The symmetry of the experimental Raman-active modes has been assigned by comparison with theoretical data. In addition to the Raman-active modes, two additional Raman features are also detected, whose intensity increases with compression. The origin of these two additional peaks addressed in this study, reveals a strong dependence on the geometry and the low dimensionality as the most plausible explanation.

Effect of dispersant on the synthesis of cotton textile waste-based activated carbon by FeCl2 activation: characterization and adsorption properties

Considering the accumulation and high consumption of activating agents, anhydrous ethanol (AE) could be used to dissolve them to improve the dispersion effect, which was an effective way of improving the practical utilization rate. In this study, FeCl₂ was dissolved in AE and further impregnated cotton textile waste (CTW) to prepare activated carbons (ACs) by pyrolysis. Afterward, ACs prepared in optimal conditions determined by the orthogonal experiment evaluated the physicochemical properties and adsorption capacities for Cr(VI). The results illustrated that AE greatly increased the dispersion of FeCl₂ on CTW, reduced the conventional impregnation dosage, and remarkably improved the activation efficiency. Textural analyses revealed that ACs exhibited excellent porosity properties and graphite carbon structure. FeCl₂ catalyzed the decomposition of volatile substances to produce gaseous products and promoted the transformation of amorphous carbon to graphite carbon that was conducive to pore development, followed by the formation of developed micropores and crystal structures. The adsorption performance of ACs was estimated using Cr(VI), and the adsorption was fitted with the pseudo-second-order kinetic and the Langmuir isotherm. Furthermore, the ACs possessed superior magnetization and reusability. Graphical abstract.

Dye removal from water and wastewater by nanosized metal oxides - modified activated carbon: a review on recent researches

The conventional water and wastewater treatment methods are unable to provide up-to-data organized standards for drinking water and discharging effluents into natural ecosystems. Therefore, developing advanced and cost-effective methods to achieve published standards for water and wastewater and population needs are nowadays necessity. The important parts of this article are providing literature information about dyes and their effects on the environment and human health, adsorption properties and mechanism, adsorbent characteristics, and recent information on various aspects of modified activated carbons with nanosized metal oxides (AC- NMOs) in the removal of dyes. This review also summarized the effect of main environmental and operational parameters such as adsorbent dosage, pH, initial dye concentration, contact time, and temperature on the dye adsorption using AC-NMOs. Furthermore, the applied isotherm and kinetic models have been discussed.

Magnetic nanoparticles incorporation into different substrates for dyes and heavy metals removal-A Review

Substantial discharge of hazardous substances, especially dyes and heavy metal ions to the environment, has become a global concern due to many industries neglecting the environmental protocols in waste management. A massive discharge of contaminantsfrom different anthropogenic activities, can pose alarming threats to living species and adverse effect to the ecosystem stability. In the process of treating the polluted water, various methods and materials are used. Hybrid nanocomposites have attained numerous interest due to the combination of remarkable features of the organic and inorganic elements in a single material. In this regards, carbon and polymer based nanocomposites have gained particular interest because of their tremendous magnetic properties and stability. These nanocomposites can be fabricated using several approaches that include filling, template, hydrothermal, pulsed-laser irradiation, electro-spinning, detonation induced reaction, pyrolysis, ball milling, melt-blending, and many more. Moreover, carbon-based and polymer-based magnetic nanocomposites have been utilized for an extensive number of applications such as removal of heavy metal and dye adsorbents, magnetic resonance imaging, and drug delivery. This review emphasized mainly on the production of magnetic carbon and polymer nanocomposites employing various approaches and their applications in water and wastewater treatment. Furthermore, the future opportunities and challenges in applying magnetic nanocomposites for heavy metal ion and dye removal from water and wastewater treatment plant.

Single-step pyrolysis for producing magnetic activated carbon from tucumã (Astrocaryum aculeatum) seed and nickel(II) chloride and zinc(II) chloride. Application for removal of nicotinamide and propanolol

The present research describes the synthesis of new nanomagnetic activated carbon material with high magnetization, and high surface area prepared in a single pyrolysis step that is used for the carbonization, activation, and magnetization of the produced material. The pyrolysis step of tucumã seed was carried out in a conventional tubular oven at 600 °C under N₂-flow. It was prepared three magnetic carbons MT-1.5, MT-2.0, MT-2.5, that corresponds to the proportion of biomass: ZnCl₂ always 1:1 and varying the proportion of NiCl₂ of 1.5, 2.0, and 2.5, respectively. These magnetic nanocomposites were characterized by Vibrating Sample Magnetometer (VSM), X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, hydrophobic/hydrophilic balance, CHN/O elemental analysis, modified Boehm titration, N₂ adsorption-desorption isotherms; and pH_pzc. All the materials obtained presented Ni particles with an average crystallite size of less than 33 nm. The MT-2.0 was employed for the removal of nicotinamide and propranolol from aqueous solutions. Based on Liu isotherm, the Q_max was 199.3 and 335.4 mg g^-1 for nicotinamide and propranolol, respectively. MT-2.0 was used to treat simulated pharmaceutical industry effluents attaining removal of all organic compounds attaining up to 99.1 % of removal.

Comparative and Equilibrium Studies on Anionic and Cationic Dyes Removal by Nano-Alumina-Doped Catechol Formaldehyde Composite

Nano-alumina-doped catechol formaldehyde polymeric composite was prepared, characterized, and applied as an adsorbent for the removal of an anionic dye Congo red (CR) and a cationic dye SafraninO (SF), by adsorption process especially from aqueous solutions. Characterizations such as particle size distribution, zeta potential, BET, FTIR, and FESEM-EDAX were carried out for the adsorbent prepared. All experiments were conducted at the batch condition to study the effects of initial dye concentration (CR: 30–90 mg/L and SF: 10–50 mg/L), pH (2–11), temperature (25–55°C), and adsorbent dosage (0.05–0.3 g) on dye removal. The isotherm models (Langmuir, Freundlich, and Temkin) were analyzed for this adsorption work. The kinetic data obtained were analyzed by the pseudo-first-order, pseudo-second-order, Bangham, and Chien–Clayton equations. Dyes adsorption data were well fitted with the Freundlich isotherm equilibrium model and the pseudo-second-order kinetic model. Study results suggested that the nano-alumina-polymeric composite could be an effective adsorbent for anionic dye rather than cationic dye.

Application of Efficient Magnetic Particles and Activated Carbon for Dye Removal from Wastewater

Since the turn of the 21st century, water pollution has been a major issue, and most of the pollution is generated by dyes. Adsorption is one of the most commonly used dye-removal methods from aqueous solution. Magnetic-particle integration in the water-treatment industry is gaining considerable attention because of its outstanding physical and chemical properties. Magnetic-particle adsorption technology shows promising and effective outcomes for wastewater treatment owing to the presence of magnetic material in the adsorbents that can facilitate separation through the application of an external magnetic field. Meanwhile, the introduction of activated carbon (AC) derived from various materials into a magnetic material can lead to efficient organic-dye removal. Therefore, this combination can provide an economical, efficient, and environmentally friendly water-purification process. Although activated carbon from low-cost and abundant materials has considerable potential in the water-treatment industry, the widespread applications of adsorption technology are limited by adsorbent recovery and separation after treatment. This work specifically and comprehensively describes the use of a combination of a magnetic material and an activated carbon material for dye adsorption in wastewater treatment. The literature survey in this mini-review provides evidence of the potential use of these magnetic adsorbents, as well as their magnetic separation and recovery. Future directions and challenges of magnetic activated carbon in wastewater treatment are also discussed in this paper.

Magnetic Fe3O4 Nanoparticle Biochar Derived from Pomelo Peel for Reactive Red 21 Adsorption from Aqueous Solution

In this study, Fe3O4 nanoparticle-loaded biochar derived from the pomelo peel (FO-PPB) was synthesized and applied as an affordable material for the adsorption of Reactive Red 21 (RR21) in an aqueous solution. The characteristics of FO-PPB were evaluated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), Raman spectra, Fourier transform infrared spectra (FTIR), and Brunauer–Emmett–Teller (BET) surface area. The adsorption process of FO-PPB with RR21 was evaluated through batch experiments to examine various parameters including solution pH, contact time, adsorbent dose, initial RR21 concentration, and solution temperature. Results show that FO-PPB produced by the impregnation ratio between iron (Fe) and pomelo peel biochar (PPB) of 5 : 1 (w/w) had the best adsorption performance. The adsorption capacities of PPB and FO-PPB at optimum experimental conditions (solution pH 3, contact time of 60 min, solution temperature of 40°C, initial RR21 concentration of 300 mg/L, and adsorbent dose of 2 g/L) were 18.59 and 26.25 mg/g, respectively. The adsorption isotherms of RR21 on PPB and FO5-PPB were described well by Langmuir and Sips models with high R2 values of 0.9826 and 0.9854 for FO5-PPB and 0.9701 and 0.9903 for PPB, respectively. The obtained data also well matched the pseudo-first-order and pseudo-second-order models with R2 values ≥ 0.96. Chemisorption through sharing or electronic exchange was determined as the main adsorption mechanism.

Efficient Removal of Diclofenac from Aqueous Solution by Potassium Ferrate-Activated Porous Graphitic Biochar: Ambient Condition Influences and Adsorption Mechanism

Porous graphitic biochar was synthesized by one-step treatment biomass using potassium ferrate (K₂FeO₄) as activator for both carbonization and graphitization processes. The modified biochar (Fe@BC) was applied for the removal of diclofenac sodium (DCF) in an aqueous solution. The as-prepared material possesses a well-developed micro/mesoporous and graphitic structure, which can strengthen its adsorption capacity towards DCF. The experimental results indicated that the maximum adsorption capacity (q_max) of Fe@BC for DCF obtained from Langmuir isotherm simulation was 123.45 mg·L⁻¹ and it was a remarkable value of DCF adsorption in comparison with that of other biomass-based adsorbents previously reported. Thermodynamic quality and effect of ionic strength studies demonstrated that the adsorption was a endothermic process, and higher environmental temperatures may be more favorable for the uptake of DCF onto Fe@BC surface; however, the presence of NaCl in the solution slightly obstructed DCF adsorption. Adsorption capacity was found to be decreased with the increase of solution pH. Additionally, the possible mechanism of the DCF adsorption process on Fe@BC may involve chemical adsorption with the presence of H-bonding and π–π interaction. With high adsorption capacity and reusability, Fe@BC was found to be a promising absorbent for DCF removal from water as well as for water purification applications.

High index facet bounded α-Fe2O3 pseudocubic nanocrystals with enhanced electrochemical properties: Zn2+ ion assisted solvo-hydrothermal synthesis

Pseudocubic α-Fe₂O₃ nanocrystals were grown by a surfactant-free, low temperature, solvo-hydrothermal process and characterised by XRD, FESEM, TEM, FTIR, Raman, XPS and UV-vis analysis.

Adsorptive Removal of Methylene Blue and Crystal Violet onto Micro-Mesoporous Zr3O/Activated Carbon Composite: A Joint Experimental and Statistical Modeling Considerations

Zirconium oxide/activated carbon (Zr3O/AC) composite was synthesized to remove methylene blue (MB) and crystal violet (CV) from the aqueous medium. The Zr3O/AC sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analyses (EDS), Raman spectroscopy (RS), BET surface area, and Fourier transform infrared spectroscopy (FTIR). XRD profiles confirmed the successful synthesis of the zirconium oxide/activated carbon composite. SEM images showed multideveloped walls with irregular particle size with channel arrays. The nitrogen physisorption combines I and IV types with a calculated BET surface area of 1095 m2/g. Raman spectrum illustrated a disorder of both crystalline structure and the graphitic structure. The adsorption was better fitted to the pseudo-second-order (PSO) kinetic model. Langmuir model fitted better the experimental results of MB adsorption, whereas the CV was better consistent with the Freundlich model. The obtained results suggested that the MB and CV adsorption might be influenced by the mass transfer that involves multiple diffusion steps. The maximum adsorption capacities are 208.33 and 204.12 mg/g for MB and CV, respectively. The MB and CV removal mechanisms were proposed, and statistical optimization was performed using central composite design combined with the response surface methodology.

Activated magnetic biochar by one-step synthesis: Enhanced adsorption and coadsorption for 17β-estradiol and copper

In this study, activated magnetic biochars (AMBCs) were successfully synthesized via one-step synthetic method with different temperature (300, 500 and 700 °C). Characterization experiments indicated that AMBCs had larger surface area, higher pore volume and more contained‑oxygen functional groups compared to the pristine biochar. In addition, AMBCs showed better adsorption performance for 17β-estradiol (E2) and copper (Cu(II)) in single/binary-solute systems than unmodified pristine biochar. AMBC-700 exhibited the highest capacity (153.2 mg/g) for E2, while the AMBC-300 showed the best adsorption capacity (85.93 mg/g) for Cu(II) in single-solute system. Adsorption of Cu(II) and E2 both followed by pseudo-second-order and Langmuir isothermal model. The initial pH of the solution had an effect on the adsorption of E2 and Cu(II) in single-solute system. Coadsorption experiments indicated that there existed site competition and enhancement of E2 and Cu(II) on the sorption in binary-solute system. Results from this study indicated that the E2 was adsorbed by hydrogen bonds, π-π EDA interactions. Cu(II) was mainly adsorbed via chemical complexation between contained‑oxygen functional groups and Cu(II) ions. Therefore, the AMBCs via one-step synthesis could be converted into value-added biochar as effective sorbent for simultaneous removal of E2 and Cu(II) from water.

Fabrication of novel sandwich nanocomposite as an efficient and regenerable adsorbent for methylene blue and Pb (II) ion removal

An adsorbent, which is easy to be separated and reused after adsorption, is very important for the removal of pollutants in aqueous solution. Hence, a novel nanofibrous sandwich structured adsorbent of silica nanofiber/magnetite nanoparticles/porous silica (SNF/MNP/PS) was designed and synthesized for the first time. The magnetite nanoparticles with diameter less than 10 nm were evenly distributed on the surface of silica nanofiber, which was subsequently fully covered by a layer of porous silica. The novel adsorbent was proved possessing good adsorption capacity for both methylene blue (MB) and Pb (II) ion (Pb²⁺), and the adsorption equilibrium could be well described by the Langmuir-isotherm model with the maximum adsorption capacity of 103.1 mg/g for MB and 243.9 mg/g for Pb²⁺ at 288 K. Moreover, in MB-Pb²⁺ mixed system the measured adsorption capacity reached 74.5 mg/g for MB and 202.4 mg/g for Pb²⁺, respectively. The saturated adsorbent could be readily magnetically separated from the solution and then efficiently regenerated by heterogeneous Fenton-like reaction (for MB) or acidic desorption process (for Pb²⁺), respectively. After 5 cycles of adsorption-regeneration, the adsorption capacity of the reused adsorbent still reached 81.0% (for MB) and 70.9% (for Pb²⁺) of the initial value. The SNF/MNP/PS behaves good adsorption properties for different types of pollutants, high magnetic recoverability and regeneration efficiency, which make it applicable to different contaminants removal.

Facile synthesis of surface-functionalized magnetic nanocomposites for effectively selective adsorption of cationic dyes

A new magnetic nano-adsorbent, polycatechol modified Fe₃O₄ magnetic nanoparticles (Fe₃O₄/PCC MNPs) were prepared by a facile chemical coprecipitation method using iron salts and catechol solution as precursors. Fe₃O₄/PCC MNPs owned negatively charged surface with oxygen-containing groups and showed a strong adsorption capacity and fast adsorption rates for the removal of cationic dyes in water. The adsorption capacity of methylene blue (MB), cationic turquoise blue GB (GB), malachite green (MG), crystal violet (CV) and cationic pink FG (FG) were 60.06 mg g^- 1, 70.97 mg g^- 1, 66.84 mg g^- 1, 66.01 mg g^- 1 and 50.27 mg g^- 1, respectively. The adsorption mechanism was proposed by the analyses of the adsorption isotherms and adsorption kinetics of cationic dyes on Fe₃O₄/PCC MNPs. Moreover, the cationic dyes adsorbed on the MNPs as a function of contact time, pH value, temperature, coexisting cationic ions and ion strength were also investigated. These results suggested that the Fe₃O₄/PCC MNPs is promising to be used as a magnetic adsorbent for selective adsorption of cationic dyes in wastewater treatment.

Fabrication of cotton textile waste-based magnetic activated carbon using FeCl3 activation by the Box–Behnken design: optimization and characteristics

Cotton textile waste-based magnetic activated carbon was prepared via simultaneous activation-pyrolysis using FeCl₃ as a novel activating agent.

Efficient removal of amoxicillin and paracetamol from aqueous solutions using magnetic activated carbon

Activated carbon (AC)/CoFe₂O₄ nanocomposites, MAC-1 and MAC-2, were prepared by a simple pyrolytic method using a mixture of iron(III)/cobalt(II) benzoates and iron(III)/cobalt(II) oxalates, respectively, and were used as efficient adsorbents for the removal of amoxicillin (AMX) and paracetamol (PCT) of aqueous effluents. The synthesized nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The sizes of cobalt ferrite nanoparticles formed from benzoates of iron(III)/cobalt(II) and oxalates of iron(III)/cobalt(II) precursors were in the ranges of 5-80 and 6-27 nm, respectively. The saturation magnetization (M _s), remanence (M _r) and coercivity (H _c) of the MAC-2 nanocomposites were found to be 3.07 emu g^-1, 1.36 emu g^-1 and 762.49 Oe; for MAC-1, they were 0.2989 emu g^-1, 0.0466 emu g^-1 and 456.82 Oe. The adsorption kinetics and isotherm studies were investigated, and the results showed that the as-prepared nanocomposites MAC-1 and MAC-2 could be utilized as an efficient, magnetically separable adsorbent for environmental cleanup. The maximum sorption capacities obtained were 280.9 and 444.2 mg g^-1 of AMX for MAC-1 and MAC-2, respectively, and 215.1 and 399.9 mg g^-1 of PCT using MAC-1 and MAC-2, respectively. Both adsorbents were successfully used for simulated hospital effluents, removing at least 93.00 and 96.77% for MAC-1 and MAC-2, respectively, of a mixture of nine pharmaceuticals with high concentrations of sugars, organic components and saline concentrations.

Selective removal of toxic anionic dyes using a novel nanocomposite derived from cationically modified guar gum and silica nanoparticles

A novel nanocomposite derived from cationically modified guar gum and in-situ incorporated SiO2 NP (cat-GG/SiO2) has been developed. The cat-GG has been synthesised by grafting poly(2-(diethylamino)ethyl methacrylate) on GG backbone. Various analyses endorse the suitability of cat-GG as well-organized template for the development of homogeneous SiO2 NPs. Dye adsorption studies predict that cat-GG/SiO2 efficiently and selectively adsorb anionic dyes (reactive blue-RB and Congo red-CR) from mixture of dye solutions. This is because of high surface area, multifunctional chelating H-bonding interactions and electrostatic interactions of cationic adsorbent with anionic dyes. Dyes adsorbed on the composite surface are desorbed reversibly using pH 10 stripping solution. Besides, cat-GG/SiO2 has been recycled efficiently with no prominent loss of dye uptake capacity, even after 4 adsorption-desorption cycles.

Sustainable development of coconut shell activated carbon (CSAC) & a magnetic coconut shell activated carbon (MCSAC) for phenol (2-nitrophenol) removal

Slow pyrolysis coconut shell (CSAC) and magnetic coconut shell (MCSAC) activated carbons were prepared, characterized and used for aqueous 2-nitrophenol (2-NP) removal.