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With the development of industrial activities and the agricultural and mining industries, farmland soils are facing serious problems related to heavy metal contamination, especially cadmium (Cd) and arsenic (As) contamination. In this study, two industrial by-products, phosphogypsum (PG) and red mud (RM), were modified by lanthanum (La) impregnation to form a new composite (L-PR) to investigate the adsorption performance of Cd(II)/As(V) in both single and binary systems. The adsorption mechanisms of Cd(II)/As(V) on L-PR were analyzed using SEM, XRD, FTIR, and XPS. The passivation effect of L-PR on the Cd-As composite contaminated soil was confirmed through a soil cultivation experiment. The adsorption experiments revealed that L-PR showed superior adsorption capabilities for Cd(II) and As(V) compared to PG and RM. Additionally, L-PR was found to be less affected by changes in pH. The kinetic studies indicated that Cd(II) and As(V) adsorption by L-PR followed the second-order kinetic model most accurately. Isothermal adsorption experiments revealed that the adsorption of Cd(II) by L-PR was more in accordance with the Freundlich model, while As(V) was more in accordance with the Langmuir model. The mechanisms of Cd(II) and As(V) adsorption on L-PR involved electrostatic attraction, ion exchange, complexation, and precipitation. The adsorption of Cd(II) is dominated by complexation and precipitation, and the adsorption of As(V) is dominated by ion exchange and complexation. Soil cultivation experiments showed that L-PR significantly reduced the available Cd and As concentrations in soil by 86.01% and 27.80%, respectively, and it could induce the transformation of non-stable Cd(II)/As(V) to the more stable residual. In summary, L-PR exhibits facile preparation, excellent adsorption performance, and is capable of simultaneously removing Cd(II) and As(V) from aqueous solutions while immobilizing these contaminants in soil. These remarkable attributes made it a highly promising alternative for the simultaneous treatment of various toxic metal contaminants. [ABSTRACT FROM AUTHOR]

Constructed wetlands are an environmentally friendly and economically efficient sewage treatment technology, with fillers playing an important role in treatment processes. However, traditional wetland fillers (e.g. zeolite) are known to be imperfect because of their low adsorption capacity. In this paper, the adsorbent sodium titanate nano fillers (T3-F) was synthesized as an alternative to traditional filler with sodium titanate nanofibers (T3) as the raw material, epoxy adhesive as the adhesive agent and NH 4 HCO 3 as the pore-making agent. The properties of T3-F were characterized by powder X-ray diffraction (XRD), scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), porosity. The effect of different parameters such as pH, co-existing ions, contact time, initial metal ion concentrations and temperature was investigated for heavy metal adsorption. The results showed that the adsorption of heavy metal by T3-F followed the pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacities for Cu2+, Pb2+, Zn2+, Cd2+ were about 1.5–1.98 mmol/g, which were 4–5 times that of zeolite, the traditional commonly used filler. Moreover, T3-F could entrap toxic ions irreversibly and maintain structural stability in the adsorption process, which solved the issue of secondary pollution. In the presence of competing ions, the adsorption efficiency for Pb2+ was not reduced significantly. Adsorption was strongest at high pH. From the results and characterization, an adsorption mechanism was suggested. This study lays a foundation for the practical application of T3-F as a constructed wetland filler in the future. Image 1 • A new constructed wetland fillers was prepared by sodium titanate nanofibers. • Fillers show excellent adsorption ability towards Cu2+, Pb2+, Zn2+, Cd2+ ions. • Adsorption occurs through ion exchange mechanism. • Fillers could entrap toxic ions irreversibly. The filler can effectively adsorb heavy metal ions and permanently trap toxic cations in the fiber. [ABSTRACT FROM AUTHOR]

Adsorption of levofloxacin (LEV) onto four types of magnesium (Mg)-impregnated biochars, fabricated via thermal pyrolysis of wood chips pretreated with MgSO4 was investigated. The Mg-impregnated biochars were characterized with various tools and techniques. Batch sorption experiments were conducted to determine the sorption kinetics and isotherms of LEV onto the Mg-impregnated biochars. The pseudo-second order kinetic model described the adsorption kinetic data better than the pseudo-first order kinetic model and the Elovich equation. Due to multi-mechanisms, the Freundlich model described the experimental isotherms better than the Langmuir model. The Langmuir maximum adsorption capacities of the Mg-impregnated biochars to LEV ranged from 7.38 to 25.2 mg g−1. In the fixed-bed column experiment, higher bed height and lower flow rate led to greater LEV removal. Findings from this work indicate that Mg-impregnated biochars can be used as an alternative adsorbent to effectively remove LEV from aqueous solutions. [ABSTRACT FROM AUTHOR]

The focus of the this work is to develop mesoporous silica and amine modified sand loaded with iron (Fe) and copper (Cu) species from electroplating wastewater for a further removal of phosphorus (P) from wastewater. First, it is shown that Fe or Cu supported sand adsorbent can effectively remove phosphorus (P) from aqueous solutions. The influence of pH, initial ion concentration (C 0 ), contact time (t) on the adsorption of P by both sand adsorbents was studied. The maximum adsorption efficiency at room temperature reached 98% for the Fe-supported adsorbent under conditions of pH = 4, C 0  = 25 mg/L, t = 180min and 96.3% for the Cu-supported sand under conditions of pH = 2, C 0  = 5 mg/L, t = 120min respectively. The kinetics of P adsorption by the Fe or Cu supported sands followed the pseudo second-order kinetic model, while the adsorption isotherms fitted the Langmuir model. Based on the above results, an iron and copper co-supported sand adsorbent was prepared successfully by encapsulating Fe and Cu from a copper electroplating wastewater. In the meantime, Cu in the electroplating wastewater was reduced from 222 to 0.12 mg/L. This wastewater derived sand-based adsorbent had the same efficiency as the Fe-supported sand adsorbent. It was used to remove P from aqueous solution until the residual P in solution met China National Standard of WastewaterEmission. By this way, a dual approach to synergistically purify both anions and cations polluted wastewaters is developed. [ABSTRACT FROM AUTHOR]

MXenes are considered as an emerging class of two-dimensional (2D) adsorbent for various environmental applications. In this work, two different morphologies of Ti 3 C 2 T x MXene (multilayer (ML-Ti 3 C 2 T x) and delaminated titanium carbide (DL-Ti 3 C 2 T x)) were prepared through mild in situ HF etching and further delamination. The structural differences between the two were explored with a focus on their effects on the performance and mechanism of removing heavy metals from water. In comparison to ML-Ti 3 C 2 T x , DL-Ti 3 C 2 T x had more oxygen-containing functional groups, higher specific surface area (19.713 vs. 8.243 m2/g), larger pore volume (0.135 vs. 0.040 cm3/g), higher maximum Pb(II) adsorption capacity (77.0 vs. 56.68 mg/g), but lower maximum Cu(II) adsorption capacity (23.08 vs. 55.46 mg/g). Further investigation revealed that the removal of Pb(II) by the MXenes was mainly controlled through electrostatic attraction and surface complexation mechanisms, while Cu(II) was removed mainly through surface reduction by Ti-related groups. Because delamination of ML-Ti 3 C 2 T x increased the surface area and surface functional groups, DL-Ti 3 C 2 T x became a better sorbent for Pb(II) in water. During sonication, however, delamination inevitably led to partial oxidation of Ti 3 C 2 T x nanosheets and thus weakened the reducing ability of DL-Ti 3 C 2 T x for Cu(II) in water. Nevertheless, both ML- and DL-Ti 3 C 2 T x not only exhibited excellent heavy metal adsorption capacity under different solution conditions, but also showed good reusability. Findings of this study indicate that Ti 3 C 2 T x MXenes are promising adsorbents for treating heavy metal pollutants in water. [Display omitted] • Multilayer and delaminated Ti 3 C 2 T x showd great potential in removing heavy metals. • Delamination raised the surface area of Ti 3 C 2 T x , enhancing Pb(II) adsorption. • Delamination oxidized Ti 3 C 2 T x nanosheets, reducing their Cu(II) reduction ability. [ABSTRACT FROM AUTHOR]

Highlights: [•] Adsorption of ciprofloxacin was conducted by carbon from aqueous solution. [•] Adsorption of Ni(II) was conducted by carbon from aqueous solution. [•] Cosorption of ciprofloxacin and Ni(II) was investigated. [•] The addition of ciprofloxacin suppressed the adsorption of Ni(II) onto carbon. [•] The presence of Ni(II) increased the adsorption of CIP in certain pH range. [ABSTRACT FROM AUTHOR]

Abstract: Preparation of highly developed mesoporous activated carbons from renewable source Arundo donax Linn was performed using H4P2O7 as activator. The influences of chemical impregnation ratio (mass of H4P2O7:A. donax Linn), activation temperature and soaking time on the properties (yield, BET surface area, pore volume and surface functional group) of activated carbon were investigated. The optimal activated carbon (ALAC) was characterized by scanning electron micrograph (SEM), N2 adsorption/desorption isotherms, X-ray photoelectron spectrometry (XPS) and oxytetracycline (OTC) adsorption experiments. Results showed that the pore development was significant at temperatures >400°C, and reached a maximum BET surface area (1463m2/g) at 600°C and maximum total pore volume (1.24cm3/g) at 500°C. At a low impregnation ratio of 0.4, BET surface area and pore volume could reach as high as 1150.69m2/g and 0.59m3/g. Both BET surface area and pore volume initial increase followed by a decrease after reaching a maximum, with the maximal surface area was obtained at an impregnation ratio of 0.75 and maximal pore volume at 1.0. BET surface area and mesopore volume reached maximum after 10h of soaking. Acidic surface groups followed the order of: strong acidic groups>weak acidic groups>intermediate acidic groups. Low activation temperature was favorable to the formation of acidic surface functional groups. With the increase of soaking time, the acidic surface functional initial increase was followed by a gradual decrease and finally tended to level off. [Copyright &y& Elsevier]

Abstract: A composite sorbent (ACprepared by grafting amine-group onto activated carbon (AC). Both raw AC and ACcharacterized by scanning electron microscopy (SEM), Fourier transformed infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). Batch experiments with variable pH, time, and concentrations of Cr(VI) were conducted to evaluate the sorption performance of Cr(VI) by both adsorbents from aqueous solutions. The total chromium in the aqueous solution was also recorded to study the mechanism of adsorption/transformation of Cr(VI). The ratio of the amount of Cr(VI) to Cr(III) on the sorbent was confirmed by the XPS analysis results. Langmuir, Freundlich and Temkin adsorption isotherms were used to fit the experimental equilibrium data and values of the parameters of the isotherms were reported. When compared with the untreated activated carbon, the modified activated carbon provided more faster kinetics and the sorbent exhibits greater adsorption capacity for chromium(VI) by comparing the maximum adsorption capacity calculated by Langmuir model. Overall, ACffectively remove Cr(VI) from aqueous solutions under a wide range of experimental conditions. [Copyright &y& Elsevier]

Abstract: Two activated carbons employing Cyperus alternifolius as precursor were produced by using two different activating agents, H3PO4 and H4P2O7 (AC-H3PO4 and AC-H4P2O7). Both of activated carbons were allowed by single-step to get carbonized at 450°C in a muffle furnace for 1h. Activated carbons differed with the physical structure and chemical properties which were derived from Scanning Electron Microscope, N2 adsorption/desorption isotherms and Fourier-transform infrared spectroscopy (FTIR). Batched sorption studies were performed to compare the ciprofloxacin (CIP) adsorption properties of two carbons. The results indicated that AC-H3PO4 had 1066.4m2/g of surface area and 1.151cm3/g of total pore volume, while AC-H4P2O7 had 1040.3m2/g of surface area and 1.227cm3/g of total pore volume. Moreover, AC-H4P2O7 exhibited a higher portion of mesopores than AC-H3PO4. Fourier transform infrared spectra indicated two samples had similar functional groups. For both adsorbents, the adsorption kinetics followed the pseudo-second-order model. The adsorption equilibrium data were very well represented by three commonly used isotherm model for AC-H3PO4 (Langmuir, Freundlich and Temkin equations). As for AC-H4P2O7, the adsorption isotherm models fitted the data in the order: Langmuir>Temkin>Freundlich isotherms. The thermodynamic parameters indicated that the adsorption of CIP onto both adsorbents was spontaneous and thermodynamically favorable, with exothermic nature of the adsorption of CIP onto AC-H3PO4 and endothermic nature onto AC-H4P2O7. [Copyright &y& Elsevier]

Lanthanun oxide (La2O3) is a lanthanum chemical compound incorporates a sensible anionic complexing ability; however, it lacks stability at a low pH scale. Biochar fibers will give the benefit of their massive space and plethoric uses on the surface to support a metal chemical compound. Herein, wet spinning technology was used to load La3+ onto sodium alginate fiber, and to convert La3+ into La2O3 through carbonization. The La2O3-modified biochar (La-BC) fiber was characterized by SEM, XRD and XPS, etc. An adsorption experiment proved that La-BC showed an excellent adsorption capacity for chromates, and its saturation adsorption capacity was about 104.9 mg/g. The information suggested that the adsorption was in step with both the Langmuir and Freundlich models, following pseudo-second-order surface assimilation mechanics, which showed that the Cr (VI) adsorption was characterized by single-phase and polyphase adsorption, mainly chemical adsorption. The thermodynamic parameters proved that the adsorption process was spontaneous and endothermic. The mechanistic investigation revealed that the mechanism of the adsorption of Cr (VI) by La-BC may include electrostatic interaction, ligand exchange, or complexation. Moreover, the co-existing anions and regeneration experiments proved that the La-BC is recyclable and has good prospects in the field of chrome-containing wastewater removal. [ABSTRACT FROM AUTHOR]

Highlights: [•] The lignin-based activated carbon was prepared by physical activation with steam. [•] The influences of various process parameters were investigated. [•] The optimum preparation conditions were determined. [•] The lignin-based carbon prepared by steam activation exhibited a mesoporous structure. [•] The static adsorption experiment and adsorption isotherms were studied. [Copyright &y& Elsevier]

Abstract: Low-cost activated carbon with high surface area was prepared from lignin of papermaking black liquor (BL) by KOH activation with pre-carbonization method. The effects of lignin/KOH ratio, activation temperature and activation time on the BET surface area were investigated. In addition, the adsorption capacity of Ni(II) on BLAC was also studied. Through BET surface area, scanning electron microscopy, Fourier transformed infrared spectroscopy and thermo gravimetric analysis, the BL-activated carbon (BLAC) was discovered to have porous structure with a high surface area up to 2943m2/g. The results showed that the lignin/KOH ratio was the main factor influencing the surface area and the maximum surface area activated carbon was obtained at lignin/KOH ratio of 3:1, the activation temperature of 750°C and the activation time of 1h. The sorption experiments indicated that the pseudo-second-order model was well fitted the kinetic data and the adsorption equilibrium data were better simulated by Langmuir model. The adsorption ability of Ni(II) increased with increasing pH, indicating the electrostatic attraction mechanism. [Copyright &y& Elsevier]

Abstract: Using first-principles calculations, we investigate magnetic properties and electronic structures of graphene with H, N and P adsorptions. With a change in adsorption density from 1/50 to 1/162 a band gap changing from ∼1.2 to 0.1eV emerges in a H-absorbed graphene, leading to the semiconducting graphene and showing ferromagnetism with the magnetic moment of the system changing from 0.76 to 0.42μ B. The unpaired electrons in the absorbed N/P atoms are polarized and thus it exhibits magnetic moment per N/P atom changing from 0.38/0.20 to 0.60/0.14μ B and metallic and half-metallic magnetism, respectively. The spin-polarized graphene system has a great application prospect in spintronics. [ABSTRACT FROM AUTHOR]