Production of aminated peat from branched polyethylenimine and glycidyltrimethylammonium chloride for sulphate removal from mining water

Development of recoverable adsorbents for Cr(VI) ions by grafting of a dimethylamino group-containing monomer on polyethylene substrate and subsequent quaternization

A polymeric adsorbent for removal of hexavalent chromium (Cr(VI)) ions was developed by the photografting of 2-(dimethylamino)ethyl methacrylate (DMAEMA) to a polyethylene (PE) mesh and subsequent quaternization with iodoalkanes of different alkyl chain lengths. The grafting of DMAEMA and subsequent quaternization were verified by the FT-IR and XPS measurements. The Cr(VI) ion adsorption capacity of the DMAEMA-grafted PE meshes had the maximum value at the grafted amount of 2.6 mmol/g in a 0.20 mM K₂Cr₂O₇ solution at pH 3.0 and 30°C. The adsorption behaviour obeyed the pseudo-second order kinetic model and well expressed by Langmuir isotherm. These results suggest that the Cr(VI) ion adsorption occurs through the electrostatic interaction mainly between protonated dimethylamino groups and hydrochromate (HCrO₄^-) ions. The adsorption capacity of the quaternized PE-g-PDMAEMA meshes increased with an increase in the degree of quaternization and/or the alkyl chain length of the iodoalkanes used and the maximum adsorption ratio was obtained at the degree of quaternization of 54.2% for the iodoheptane-quaternized PE-g-PDMAEMA (PE-g-QC₇PDMAEMA) mesh. This value was about 1.86 times higher than that of the PE-g-PDAMEMA mesh. Cr(VI) ions were successfully desorbed from the PE-g-PDMAEMA and PE-g-QC₇PDMAEMA meshes in eluents such as NaOH, NaCl, and NH₄Cl. In 0.50 M NaCl, 0.10 M NH₄Cl, and 0.50 mM NaOH, the adsorption and desorption process was repeatedly performed without any considerable decrease and the desorption behaviour obeyed the pseudo-second order kinetic model. These results emphasise that the PE-g-PDMAEMA meshes and their quaternized products can be applied as an adsorbent for Cr(VI) ions.

Combination of adsorption/desorption and photocatalytic reduction processes for PFOA removal from water by using an aminated biosorbent and a UV/sulfite system

Per- and polyfluoroalkyl substances (PFAS) are stable organic chemicals, which have been used globally since the 1940s and have caused PFAS contamination around the world. This study explores perfluorooctanoic acid (PFOA) enrichment and destruction by a combined method of sorption/desorption and photocatalytic reduction. A novel biosorbent (PG-PB) was developed from raw pine bark by grafting amine groups and quaternary ammonium groups onto the surface of bark particles. The results of PFOA adsorption at low concentration suggest that PG-PB has excellent removal efficiency (94.8%-99.1%, PG-PB dosage: 0.4 g/L) to PFOA in the concentration range of 10 μg/L to 2 mg/L. The PG-PB exhibited high adsorption efficiency regarding PFOA, being 456.0 mg/g at pH 3.3 and 258.0 mg/g at pH 7 with an initial concentration of 200 mg/L. The groundwater treatment reduced the total concentration of 28 PFAS from 18 000 ng/L to 9900 ng/L with 0.8 g/L of PG-PB. Desorption experiments examined 18 types of desorption solutions, and the results showed that 0.05% NaOH and a mixture of 0.05% NaOH + 20% methanol were efficient for PFOA desorption from the spent PG-PB. More than 70% (>70 mg/L in 50 mL) and 85% (>85 mg/L in 50 mL) of PFOA were recovered from the first and second desorption processes, respectively. Since high pH promotes PFOA degradation, the desorption eluents with NaOH were directly treated with a UV/sulfite system without further adjustment. The final PFOA degradation and defluorination efficiency in the desorption eluents with 0.05% NaOH + 20% methanol reached 100% and 83.1% after 24 h reaction. This study proved that the combination of adsorption/desorption and a UV/sulfite system for PFAS removal is a feasible solution for environmental remediation.

Recent developments in MOF and MOF based composite as potential adsorbents for removal of aqueous environmental contaminants

With the growth of globalization which has been the primary cause of water pollution, it is utmost necessary for us living being to have access to clean water for the purpose of drinking, washing and various other useful applications. With the purpose of future security and to restore our ecological balance, it is essential to give much significance towards the removal of unwanted toxic contaminants from our water resources. In this regard adsorptive removal of toxic pollutants from wastewater with porous adsorbent is regarded as one of the most promising way for water decontamination process. Metal organic frameworks (MOFs) comprising of uniformly arranged pores, abundant active sites and containing an easily tunable structure has aroused as a promising material for adsorbent to remove the unwanted contaminants from water sources. The adsorption of pollutants by the different MOFs surface are driven by various interactions including π-π, acid-base, electrostatic and H-bonding etc. On the other hand, the removal of various contaminants by MOFs is influenced by various factors including pH, temperature and initial concentration. In this review we will specifically discuss the adsorptive removal of different organic and inorganic pollutants present in our water systems with the use of MOFs as adsorbent along with the various factors and interaction mechanism manipulating the adsorption behaviour.

Removal of Methyl Red from Aqueous Solution Using Polyethyleneimine Crosslinked Alginate Beads with Waste Foundry Dust as a Magnetic Material

In this study, a cost-effective adsorbent based on sodium alginate (SA) with waste foundry dust (WFD) was fabricated for the removal of methyl red (MR) from aqueous media. However, the utilization of WFD/SA beads to remove anionic dyes (such as MR) from effluents has limitations associated with their functional groups. To improve the adsorption performance, WFD/SA-polyethyleneimine (PEI) beads were formed via PEI crosslinking onto WFD/SA beads, which could be attributed to the formation of amide bonds from the carboxyl and amino groups due to the change of N-H bonds in the reaction. The Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) results indicated that PEI was crosslinked on the WFD/SA via a chemical reaction. In the FTIR spectra of WFD/SA-PEI, peaks of the –COO (asymmetric) stretching vibration shifted to 1598 and 1395 cm⁻¹, which could be attributed to the hydrogen-bonding effect of the N–H groups in PEI. In the N1s spectrum, three deconvoluted peaks were assigned to N in –N= (398.2 eV), –NH/–NH₂ (399.6 eV), and NO₂ (405.2 eV). WFD/SA-PEI beads were assessed and optimized for aqueous MR adsorption. The WFD/SA-PEI beads showed a high removal efficiency for MR (89.1%) at an initial concentration of 1000 mg/L, and presented a maximum MR adsorption capacity of 672.7 mg/g MR. The adsorption process showed a good fit with the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model. The amino and hydroxyl groups in the WFD/SA-PEI beads facilitate strong hydrogen bonding and electrostatic interactions. Moreover, these WFD/SA-PEI beads were easily recovered after the adsorption process.

Vanadium removal by cationized sawdust produced through iodomethane quaternization of triethanolamine grafted raw material

In this study, two-step surface modification of sawdust using triethanolamine (at 180 °C) and iodomethane (at 42 °C) was performed to produce a novel quaternized biosorbent, TEA-I-SD. The characterization studies revealed significant morphological changes in the sawdust and successful quaternization with a nitrogen content of 5.75%. The highest vanadium removal (96.2%) was achieved at pH 4 (dosage 1 g/L, initial vanadium concentration 19.1 mg/L). Equilibrium was achieved within 8 h of contact time and the adsorption kinetics were well fitted with the pseudo-second-order model. Both film diffusion and intra-particle diffusion contributed to the adsorption process, while the latter was the rate-limiting step. The maximum vanadium adsorption capacity of TEA-I-SD (35.0 mg/g, pH 4) was close to the theoretical value obtained from the Langmuir model. The best fit was achieved with the Redlich-Peterson model, exhibiting a monolayer adsorption phenomenon. Tests with real mine water containing 11 mg/L of vanadium also confirmed its high removal (91.3%, dosage 1 g/L) using TEA-I-SD at pH 4. The TEA-I-SD could be reused three times without significant capacity loss after regeneration, although the desorption efficiency was rather low (synthetic solution: 38.5-40.5% and mine water: 26.2-43.1%).

Hexavalent chromium removal from water: adsorption properties of in natura and magnetic nanomodified sugarcane bagasse

Biosorption has become a viable and ecological process in which biological materials are employed as adsorbents for the removal of potentially toxic metals, such as hexavalent chromium, from aqueous matrices. This work proposed the use of in natura (SB) and nanomodified sugarcane bagasse (SB-NP) with ferromagnetic nanoparticles (Fe₃O₄) to adsorb Cr(VI) from water. These materials were analyzed by X-ray Spectroscopy (XRD), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FTIR) to investigate their morphology and interaction with Cr(VI). It was observed the efficient impregnation of magnetite on the SB surface and the presence of functional groups such as O-H, C-H, C=O, C-O-C, C-O, and Fe-O (characteristic of magnetite). The best conditions for Cr(VI) removal in aqueous medium were determined by assessing the pH at the point of zero charge (pH_PZC = 6.1 and 5.8 for SB and SB-NP, respectively), adsorption pH and kinetics, and adsorption capacity. Batch procedures were performed using increasing concentrations of Cr(VI), 10-100 mg/L at pH 1.0, and 30 min of contact time. The adsorbent dose was 10 mg/L, and the experimental adsorption capacities (SC_exp) for SB, NP, and SB-NP were 1.49 ± 0.06 mg/g, 2.48 ± 0.57 mg/g, and 1.60 ± 0.08 mg/g, respectively. All Cr contents were determined by flame atomic absorption spectrometry (FAAS). The pseudo-2nd-order kinetic equation provided the best adjustments with r² 0.9966 and 0.9931 for SB and SB-NP, respectively. Six isotherm models (Langmuir, Freundlich, Sips, Temkin, Dubinin-Radushkevich, and Hill) were applied to the experimental data, and Freundlich, Dubinin-Radushkevich (D-R), and Temkin were the models that best described the experimental sorption process. The binding energy values (E) provided by the D-R model were 0.11 ± 0.25, 0.09 ± 0.20, and 0.08 ± 0.25 kJ/mol, for NP, SB-NP, and SB, respectively, and denote a physical interaction for the studied adsorbate-adsorbent system. The nanomodification of the biomass slightly improved the efficiency for the sorption of Cr(VI) and facilitated the removal of Cr(VI)-containing biosorbents from water medium.

Efficient adsorption of diclofenac sodium in water by a novel functionalized cellulose aerogel

In this work, a novel cellulose aerogel (CNC-PVAm/rGO) was fabricated using cellulose nanocrystalline (CNC) modified with polyvinylamine (PVAm) and reduced graphene oxide (rGO). The resultant CNC-PVAm/rGO was then applied for the adsorption of diclofenac sodium (DCF), a typical non-steroidal anti-inflammatory drug. Characterization using ultra-high-resolution field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and the Brunauer-Emmett-Teller surface area revealed that the obtained CNC-PVAm/rGO displayed an evident 3D porous structure, which had an ultralight weight, good recovery, abundant surface functional groups (e.g., -NH₂ and -OH), and rGO nanosheets. In addition, the material presented a stable crystal structure and large specific surface area (105.73 m² g^-1). During the adsorption of DCF, the CNC-PVAm/rGO aerogel showed a rather excellent adsorption performance, with a maximum adsorption capacity (q_max) of 605.87 mg g^-1, which was approximately 53 times larger than that of the bare CNC aerogel (11.45 mg g^-1). The adsorption performance of CNC-PVAm/rGO was also better than that of other reported adsorbents. The adsorption of DCF to CNC-PVAm/rGO obeyed the Langmuir isotherm and pseudo-second-order kinetic models, and underwent a spontaneous exothermic process. Moreover, DCF was easily desorbed from CNC-PVAm/rGO with sodium hydroxide solution (0.1 mol L^-1), and the absorbent could be reused four times. The introduction of PVAm and rGO to the CNC-PVAm/rGO aerogel also greatly enhanced electrostatic interactions, π-π interactions, and hydrophobic effects. These enhancements significantly promoted the hydrogen bonding interactions between the DCF molecules and CNC-PVAm/rGO, thus resulting in a large improvement in the adsorption performance of the aerogel.

Facile green synthesis of ZnO-CdWO4 nanoparticles and their potential as adsorbents to remove organic dye

In this work, ZnO-CdWO₄ nanoparticles have been synthesized by the ecofriendly green method with lemon leaf extract to favorably anchor functional groups on their surface. The prepared ZnO-CdWO₄ nanoparticles are used as adsorbent to treat Congo red (CR) dye after characterization through FT-IR, UV-Vis, TEM, SEM-EDX, and HRTEM techniques. The equilibrium partition coefficient and adsorption capacity values for CR by ZnO-CdWO₄ are estimated as 21.4 mg g^-1 μM^-1 and 5 mg g^-1, respectively (at an initial dye concentration of 10 mg L^-1). The adsorption process is found as exothermic and spontaneous, as determined by the ΔG°, ΔS°, and ΔH° values. The Boyd plot has been used as a confirmatory tool to fit the adsorption kinetics data along with intraparticle diffusion and pseudo-second-order models. Based on this research, ZnO-CdWO₄ nanoparticles are validated as an effective adsorbent for CR dye in aqueous solutions.

Acid mine drainage treatment with novel high-capacity bio-based anion exchanger

Aminated peat (termed PG-Peat) produced using polyethylenimine and glycidyltrimethylammonium chloride was used for the removal of sulphate from real acid mine drainage (AMD) in batch and column mode sorption studies. In the batch tests, the highest sulphate removal capacity achieved was 125.7 mg/g. PG-Peat was efficient and rapid in sulphate removal from AMD even at low temperatures (2-5 °C), achieving equilibrium within a contact time of 30 min. The PG-Peat column treating real AMD showed even higher sulphate uptake capacity (154.2 mg SO₄^2-/g) than the batch sorption studies. The regenerative and practical applicability of PG-Peat was also tested in column set-ups using synthetic sulphate solutions (at pH 5.8 and pH 2.0). The sulphate uptake capacity obtained was higher in column mode when the solutions were treated at acidic pH (2.0) compared to pH 5.8. This could be attributed to the presence of cationized amine groups on PG-Peat under acidic pH conditions. Almost complete sulphate desorption was achieved with NaCl in the column that treated synthetic sulphate solution at pH 5.8, while the lowest desorption rates were observed in the column that treated acidic synthetic sulphate solution (pH 2).

Synthesis and application of cationised cellulose for removal of Cr(VI) from acid mine-drainage contaminated water

Background: Acid mine drainage (AMD) leads to contamination of surface and ground water by high levels of toxic metals including chromium. In many cases, these waters are sources of drinking water for communities, and treatment is therefore required before consumption to prevent negative health effects. Methods: Cationised hemp cellulose was prepared by etherification with two quaternary ammonium salts: 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHPTAC) and glycidyltrimethylammonium chloride (GTMAC) and examined for (i) the efficiency of Cr(VI) removal under acid mine-drainage (AMD) conditions, and (ii) antibacterial activity. Adsorbents were characterised by electron microscopy, Fourier transform infrared (FTIR), CP-MAS 13C nuclear magnetic resonance (NMR) spectroscopy, elemental composition and surface charge. Results: FTIR and solid state 13C NMR confirmed the introduction of quaternary ammonium moieties on cellulose. 13C NMR also showed that cationisation decreased the degree of crystallisation and lateral dimensions of cellulose fibrils. Nevertheless, 47 %  - 72 % of Cr(VI) ions were removed from solutions at pH 4, by 0.1 g of CHPTAC and GTMAC-cationised cellulose, respectively. Adsorption kinetics followed the pseudo-second order model and isotherms were best described by the Freundlich and Dubinin-Radushkevich models. When GTMAC-modified cellulose was applied to AMD contaminated water (pH 2.7); however, Cr(VI) removal decreased to 22% likely due to competition from Al and Fe ions. Cationised materials displayed considerable antibacterial effects, reducing the viability of Escherichia coli by up to 45 % after just 3 hours of exposure. Conclusions: Together, these results suggest that cationised cellulose can be applied in the treatment of Cr(VI)-contaminated mine water particularly if pre-treatments to reduce Fe and Al concentrations are applied.

Application of a polyethylenimine-modified polyacrylonitrile-biomass waste composite fiber sorbent for the removal of a harmful cyanobacterial species from an aqueous solution

Cyanobacterial harmful algal blooms (Cyano-HABs) in water resources involving algal species such as Microcystis aeruginosa have become a serious environmental issue due to their severely negative effects. In the present study, an adsorption-based strategy was employed to control M. aeruginosa, with industrial waste-derived Escherichia coli biomass valorized to produce polyethylenimine-modified polyacrylonitrile-E. coli biomass composite fiber (PEI-PANBF). PEI-PANBF removed approximately 80% of M. aeruginosa cells from an aqueous solution without causing any cell damage. Interestingly, the thickness of PEI-PANBF had a strong influence on the efficiency of M. aeruginosa cell removal. In addition, PEI-PANBF simultaneously removed M. aeruginosa cells and their toxic secondary metabolite, microcystin-LR, from aqueous media. Thus, our proposed fiber represents a feasible utilization method of industrial waste biomass as a biosorbent for the control of Cyano-HABs.

Environmental threatening concern and efficient removal of pharmaceutically active compounds using metal-organic frameworks as adsorbents

An alarming number of contaminants of emerging concern, including active residues from pharmaceuticals and personal care products (PPCPs), are increasingly being introduced in water systems and environmental matrices due to unavoidable outcomes of modern-day lifestyle. Most of the PPCPs based contaminants are not completely eliminated during the currently used water/wastewater treatment processes. Therefore, highly selective and significant removal of PPCPs from environmental matrices remains a scientific challenge. In recent years, a wide range of metal-organic frameworks (MOFs) and MOF-based nanocomposites have been designed and envisioned for environmental remediation applications. MOF-derived novel cues had shown an adsorptive capability for the extraction and removal of an array of trace constituents in environmental samples. Noteworthy features such as substantial surface area, size, dispersibility, tunable structure, and repeated use capability provide MOFs-derived platform a superiority over in-practice conventional adsorptive materials. This review provides a comprehensive evaluation of the efficient removal or mitigation of various categories of PPCPs by diverse types of MOF-derived adsorbents with suitable examples. The growing research investigations in this direction paves the way for designing more efficient porous nanomaterials that would be useful for the elimination of PPCPs, and separation perspectives.

Modified Biopolymer Adsorbents for Column Treatment of Sulfate Species in Saline Aquifers

In the present study, variable forms of pelletized chitosan adsorbents were prepared and their sulfate uptake properties in aqueous solution was studied in a fixed-bed column system. Unmodified chitosan pellets (CP), cross-linked chitosan pellets with glutaraldehyde (CL-CP), and calcium-doped forms of these pellets (Ca-CP, Ca-CL-CP) were prepared, where the removal efficiencies and breakthrough curves were studied. Dynamic adsorption experiments were conducted at pH 4.5 and 6.5 with a specific flow rate of 3 mL/min, fixed-bed height of 200 mm, and an initial sulfate concentration of 1000 mg/L. Breakthrough parameters demonstrated that Ca-CP had the best sulfate removal among the adsorbents, where the following adsorption parameters were obtained: breakthrough time (75 min), exhaust time (300 min), maximum sulfate adsorption capacity (q_max; 46.6 mg/g), and sulfate removal (57%) at pH 4.5. Two well-known kinetic adsorption models, Thomas and Yoon-Nelson, were fitted to the experimental kinetic data to characterize the breakthrough curves. The fixed-bed column experimental results were well-fitted by both models and the maximum adsorption capacity (46.9 mg/g) obtained was for the Ca-CP adsorbent. A regeneration study over four adsorption-desorption cycles suggested that Ca-CP is a promising adsorbent for sulfate removal in a fixed-bed column system.

Adsorption of sulfate ion from water by zirconium oxide-modified biochar derived from pomelo peel

Zirconium oxide-modified pomelo peel biochar (ZrBC) was synthesized for the adsorption of sulfate ion from aqueous solution. Zirconyl chloride octahydrate (ZCO) was used to modify pomelo peel biochar into ZrBC. The optimal dose of ZCO for modification is 0.5 mol/L, at which ZrBC shows the highest adsorption of sulfate ion. The adsorbents were characterized by the field emission scanning electron microscopy, X-ray photoelectron spectroscopy and surface area measurement. The results confirm that the presence of zirconium oxides and hydroxide groups on the ZrBC surface, and ZrBC has a porous structure and a higher specific surface area in comparison with pomelo peel biochar. ZrBC shows good affinity for sulfate ion with a maximum sulfate adsorption capacity of 35.21 mg/g, which is much higher than that of pomelo peel biochar (1.02 mg/g). The adsorption of sulfate on ZrBC is pH dependent, and acidic conditions favor the adsorption. The adsorption can reach near-equilibrium in approximately 120 min. The adsorption kinetics and isotherm follow the pseudo second-order equation and Langmuir adsorption model, respectively. Furthermore, nitrate and fluoride anions exhibit little influence on the adsorption of sulfate by ZrBC, whereas phosphate inhibits the adsorption under the same concentration conditions. ZrBC has the potential to be used for removal of sulfate from aqueous solution.

Design and characterization of a biomass template/SnO2 nanocomposite for enhanced adsorption of 2,4-dichlorophenol

2,4-Dichlorophenol (2,4-DCP) is a hazardous chlorinated organic chemical derived from phenol that exerts serious effects on living organisms. In the present study, SnO₂ templated with grapefruit peel carbon as a nanocomposite (SnO₂@GPC) was designed via ball-milling, and its mechanism of 2,4-DCP adsorption in aqueous solution was determined. Batch adsorption experiments revealed that the maximum adsorption efficiency of SnO₂@GPC occurred at 6.0 pH, 3 mg L^-1 initial adsorbate concentration, 2 h contact time, and 293 K temperature. The SnO₂@GPC nanocomposite and its non-tin-bearing counterpart, grapefruit derived char (@GPC), showed maximum adsorption capacities (Q_L) of 45.95 and 22.09 mg g^-1 and partition coefficients of 41.77 and 10.83 mg g^-1 μM^-1, respectively. The adsorption of 2,4-DCP was best described by the Redlich-Peterson model followed by the Langmuir model with high correlation coefficients (R² ≥ 0.96), and the adsorption kinetic data best fitted the pseudo-second-order model (R² ≥ 0.98). The thermodynamic parameters indicated that the reaction was spontaneous, exothermic, and involved high affinity between SnO₂@GPC and 2,4-DCP. The high desorption efficiency obtained (>80%) demonstrated the recyclability of the adsorbent. The enhanced Q_L of SnO₂@GPC was due to the effective combination of GPC and SnO₂. A thin porous layer of GPC on SnO₂ nanoparticles provided effective channels, a large surface area, and an abundance of active sites for 2,4-DCP adsorption. Thus, the SnO₂@GPC nanocomposite could potentially be used as a low-cost adsorbent to remove 2,4-DCP from water.

Adsorptive decontamination of Cu2+-contaminated water and soil by carboxylated graphene oxide/chitosan/cellulose composite beads

Graphene adsorbents have been applied to remove diverse pollutants from aqueous systems. However, the mechanical strength of most graphene adsorbents is low and the fragile graphene sheets are released into the environment. In this study, we prepared carboxylated graphene oxide/chitosan/cellulose (GCCSC) composite beads with good mechanical strength for the immobilization of Cu²⁺ from both water and soil. The proportional limit of GCCSC beads was 3.2 N, a much larger value than graphene oxide beads (0.2 N). The largest pressure for GCCSC beads recorded before brittle failure was 26 N. The Cu²⁺ adsorption capacity of GCCSC beads was 22.4 mg/g in aqueous systems at initial Cu²⁺ concentration of 40 μg/mL, which is competitive with many efficient adsorbents. The partition coefficient (PC) for the Cu²⁺ adsorption onto GCCSC beads was 1.12 mg/g/μM at C_e of 0.83 mg/L and q_e of 14.3 mg/g. The PC decreased to 0.055 mg/g/μM at C_e of 26.0 mg/L and q_e of 22.4 mg/g. The adsorption kinetics of Cu²⁺ on GCCSC beads were moderately fast and required approximately 3 h to reach equilibrium with a k₂ of 0.0021 g/(mg·min). A lower temperature and higher pH slightly increased the adsorption capacity of GCCSC beads. The ionic strength did not influence the adsorption. The porous structure of GCCSC beads blocked the direct contact between soil and the graphene surface; thus, a high Cu²⁺ immobilization efficiency was achieved by GCCSC beads applied to soil. The implications for the design of high-performance graphene adsorbents for water and soil remediation are discussed.

A novel hierarchical stiff carbon foam with graphene-like nanosheet surface as the desired adsorbent for malachite green removal from wastewater

A novel hierarchical stiff carbon foam (HSCF) was successfully prepared via a carbothermal reduction between the carbon foam with two-level pore structure and the Al₂O₃ from aluminum sulfate, and used as a bulk adsorbent for removing malachite green (MG) dye. The structures of the HSCF were characterized using SEM, XRD, FTIR, BET, and XPS, and the effects of adsorption condition on the MG removal were studied through batch adsorption experiments. Results show that large-sized and complex-shaped HSCF can be easily fabricated with a high compression strength of 1.58 MPa at a low bulk density (0.10 g cm^-3). The HSCF possesses a fluffy graphene-like nanosheet surface with a mesoporous structure and meanwhile exhibits good hydrophilicity loaded with aluminum hydroxide. The experimental maximum adsorption capacity for MG reaches 425.2 mg g^-1 with a relatively high partition coefficient of 9.38 mg g^-1 μM^-1 at the optimal condition. The experimental data are in good agreement with Langmuir isotherm and pseudo-second-order kinetic model, and meanwhile, the adsorption of MG onto the HSCF is a spontaneous and endothermic process. Also, the HSCF still exhibits good adsorption ability and stability after seven regeneration cycles.