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Adsorption with activated carbon (AC) is an important method for the treatment of heavy metal wastewater, but there are still certain challenges in the separation and reuse of activated carbon. The preparation of magnetic activated carbon (MAC) by modifying AC is one of the effective means to realize the separation of AC from solution after the adsorption process. In this work, lignite and poplar leaves were used as raw materials for co-pyrolysis, and the co-pyrolysis char was activated and modified to prepare MAC. The structure and properties were characterized by VSM, N2 adsorption, SEM, XRD, and FT-IR. At the same time, the adsorption performance of MAC on wastewater containing Pb and Cd ions was studied. The results show that the prepared MAC contains Fe3O4, and the saturation magnetization (Ms) of the MAC is 13.83 emu/g; the specific surface area of the MAC is 805.86 m2/g, and the micropore volume is 0.23 cm3/g; the MAC exhibited a good porous structure. When the pH value of the solution was 5, the adsorption time was 120 min, the dosage of MAC was 4 g/L, the initial concentration of Pb ion solution was 50 mg/L, and that of Cd ion solution was 25 mg/L, and the adsorption temperature was 30 °C, the adsorption efficiency of Pb, Cd ions were 84.40 and 78.80%, respectively, and the adsorption capacities were 10.55 and 4.93 mg/g, respectively. The adsorption of Pb and Cd ions by MAC conforms to the Langmuir adsorption model, which is a monolayer adsorption. The adsorption process is mainly chemical adsorption, which can be better described by the pseudo-second-order model. The adsorption thermodynamic analysis showed that the adsorption of Pb and Cd ions by MAC was a spontaneous reaction, and the higher the temperature, the stronger the spontaneity. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations are used to explore the adsorption characteristics and degradation mechanism of sulfacetamide on anatase TiO2(101) and (001) surfaces. The most probable adsorption configuration was firstly determined by comparing the adsorption energies and structural bond lengths before and after adsorption. After adsorption, some of the bond lengths are elongated. We have proposed about six possible degradation pathways of sulfacetamide, such as branch chain breaking, benzene ring dihydroxylation, amino substitution and sulphur nitrogen bond breaking. And the relevant degradation processes are studied in detail. Based on the calculated results, we conclude that the TiO2(001) surface is more suitable for the degradation of sulfacetamide considering its much smaller energy barriers in several degradation paths than the TiO2(101). Among all the six possible degradation paths, we find that the hydroxyl radical attacks of C(1), C(3) and N(6) atoms of the (001) surface and the C(4) atom of (101) surface sulfacetamide are most probable reaction pathways due to their much smaller energy barriers, i.e. 7.7, 26.1 kcal mol−1 and 14.6, 23.4 kcal mol−1 indicating that these reactions can easily take place in room temperature. Our computational results are not only consistent with the experimental results of sulfacetamide degradation, but also reveal the possible microscopic mechanisms of the photocatalytic reaction. [ABSTRACT FROM AUTHOR]

The activated biochar (ABC) was prepared, characterized and examined the feasibility of removing ethylparaben (EP) from aqueous solution. The characterization results showed that ABC possessed multi-porous structure and high surface area. The adsorption isotherm was well fitted the Langmuir isotherm and the adsorption kinetic followed the pseudo-second-order model. The maximum adsorption capacity of EP onto ABC was 349.65 mg/g at 298 K. The adsorption capacity maintained 90.82% after five successive adsorption/desorption cycles. ABC possessed high adsorption capacity, usability and stability, which indicating that ABC has great potential to be a promising adsorbent for removal of EP from aqueous solution. [ABSTRACT FROM AUTHOR]

This work describes the synthesis and anti-fouling properties of poly(vinylidene fluoride) membrane, grafted with carboxybetaine-based zwitterions. An amphiphilic copolymer, poly(vinylidene fluoride)-graft- poly(N,N-dimethylamino-2-ethylmethacrylate) (PVDF-g-PDMAEMA), was synthesized by radical graft copolymerization, followed by casting the copolymer into a flat membrane, by an immersed phase inversion method. PVDF-g-PDMAEMA membrane was reacted with sodium chloroacetate (SCA) to yield a carboxybetaine-based zwitterionic surface. The membrane showed significantly enhanced hydrophilicity, due to the hydration ability of carboxybetaine-based zwitterions, which inhibited protein adsorption. Compared to pristine PVDF-g-PDMAEMA membrane, carboxybetaine-based zwitterionic membrane exhibited a higher flux recovery in the cyclic filtration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Structure and core level spectra of CoSi 2 -like to Co-rich silicides are discussed. • 200 ML Co on Si(1 1 1) forms a closed metallic Co thin film in contrast to 100 ML. • Thermostable CoSi 2 and Co-Si(1 1 1) ring clusters do not bind CO at RT. • CO adsorption at RT only occurs on Co-rich silicides and metallic Co. We report on the structure and reactivity of the Co-Si polycrystalline surfaces that form at room temperature (RT). Scanning tunneling microscopy (STM) was used to examine the surface morphology while X-ray photoelectron spectroscopy (XPS) was used to detect the chemical states of cobalt and silicon as a function of cobalt coverage. Moreover, XPS measurements after exposing the Co-Si(1 1 1) samples to CO gas provide information about CO adsorption and dissociation. When <5 ML Co is deposited on Si(1 1 1) at RT, most Co atoms diffuse into Si lattice and no CO adsorption is found at RT. This shows that coordination of Co to Si suppresses CO adsorption. Neither Co-induced Si(1 1 1)-ring cluster nor CoSi 2 crystalline film adsorb CO at RT. In contrast, CO adsorption was found at RT for cobalt doses >5 ML, an indication that Co-rich silicides and metallic Co present. The CO adsorption capacity increases with cobalt dose up to 30 ML after which it levels off, an indication that metallic cobalt sites are dominantly exposed on the surface. Furthermore, a closed metal film is formed for 200 ML dose. Some dissociation of CO was observed during heating of the CO-covered samples for Co doses ≥30 ML. [ABSTRACT FROM AUTHOR]

[Display omitted] • A comparison was made to understand the key factors in co-pyrolysis. • Analyze the effect of co-pyrolysis on the composition of pyrolysis gas and tar. • The optimal experimental conditions for activation modification were determined. • Magnetic activated carbon exhibits better adsorption and magnetic properties. Activated carbon plays an important role in the field of wastewater treatment due to its excellent adsorption, but improving the recovery and utilization efficiency of activated carbon is a major challenge for its application. In this study, lignite (LC) and poplar leaves (PL) were used as raw materials to prepare magnetic activated carbon (MAC) by co-pyrolysis and char activation modification. The adsorption performance of the product was studied. The results showed that with different blending ratios of LC and PL, a large amount of alkali metal oxides contained in PL had different promoting effects on the pyrolysis of LC. When the mass ratio of LC to PL in the mixture was 3:2, the experimental value of hydrocarbons in the obtained tar reached 53.00%, which was 7.20% higher than the calculated value. The optimal preparation conditions of MAC were determined. Under the conditions of activation temperature of 700 °C, activation time of 2 h, ZnCl 2 mass fraction of 30%, impregnation liquid–solid ratio of 3:1 and impregnation time of 16 h, the activated carbon exhibits a relatively desirable performance. The obtained products were characterized by VSM, XRD, FT-IR, N 2 adsorption and SEM. As a result, the obtained MAC exhibits a better porous structure and higher specific surface area, and Fe 3 O 4 was observed on the surface of the MAC. The adsorption performance of coking wastewater by MAC was studied. We demonstrate that the prepared MAC could effectively adsorb organic matter in wastewater. After MAC was used to adsorb the coking wastewater for 3 h, the COD concentration in the wastewater decreased from 280 to 60 mg/L, and the MAC could be effectively recovered by magnets after adsorption. [ABSTRACT FROM AUTHOR]

As one of the main pollutants of water pollution, the potential toxicity of heavy metal ions always threatens the safety of human and nature. Therefore, how to effectively remove heavy metal ions has become an important research topic in environmental protection. In the existing research, adsorption method is outstanding from many methods because of its high adsorption efficiency and easy operation. In this study, different generations of hyperbranched polyamide-amine (PAMAM) were grafted onto PVDF membrane to obtain the membrane with high adsorption capacity for heavy metal ions. The structure and physicochemical properties of the membranes were evaluated by means of fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (FE-SEM), element analyzer and X-ray photoelectron spectroscopy (EDX). At the same time, various factors affecting the adsorption process were studied, and it was found that the adsorption behavior of copper ion (Cu2+) on the membrane conformed to the pseudo-first-order kinetic model and Langmuir isotherm model. Moreover, after comparing the adsorption effect of the modified membranes grafted with different generations of PAMAM, it was found that the membrane grafted with the third generation PAMAM had the best adsorption when the solution pH was 5, and its maximum adsorption capacity could reach 153.8 mg/g. After five adsorption-desorption cycles, its adsorption capacity can reach 72.83% of the first test, indicating that it has good recycling performance. The results show that the adsorption membrane has good application potential and research value. [Display omitted] • The adsorption capacity of PVDF-g-PAMAM membrane for copper ions reached 153.8 mg/g. • The modified membranes grafted with the third generation PAMAM have the higher adsorption capacity than other modified membranes. • The steric hindrance effect and the number of amino groups have important effects on the adsorption capacity of the modified membranes. [ABSTRACT FROM AUTHOR]

A novel modified chitosan (CS) material, CS-g-AOPAM, was prepared by the amidoximation of the crosslinking compound of CS and a terpolymer of acrylamide, acrylonitrile and 3-dimethylaminoallyl phosphonic acid, which was applied to adsorb Cu(II) and Ni(II). The material CS-g-AOPAM was characterized by SEM, FTIR, XPS and TG, indicating porous structure and excellent thermal stability. In order to investigate the effects of coexisting ions, pH, initial concentration, adsorption time, and temperature on adsorption capacity of CS-g-AOPAM, batch adsorption experiments were carried out to obtain the corresponding adsorption behavior. According to the linear fitting of Langmuir model, the results proved that CS-g-AOPAM had excellent adsorption performance, exhibiting the maximum adsorption capacities of 215.5 mg·g−1 and 213.4 mg·g−1 for Cu(II) and Ni(II), respectively, which was higher than that of most similar CS adsorbents. The adsorption isotherms were in good agreement with Langmuir model, indicating a monolayer adsorption. Moreover, various adsorption kinetic and thermodynamic models were employed for analyzing adsorption behavior of CS-g-AOPAM, suggesting that the adsorption was a chemisorption as well as spontaneous endothermic process. Further, based on the analysis of FTIR and XPS, the adsorption sites and potential bonding modes of Cu(II) and Ni(II) were proposed. Overall, CS-g-AOPAM is a pretty promising novel adsorption material for the removal of heavy metal ions from wastewater. • Phosphoric acid and amidoxime groups were introduced into CS-AOPAM. • CS-AOPAM was a kind of highly effective adsorption material for Cu(II) and Ni(II). • The adsorption behavior of CS-AOPAM for Cu(II) and Ni(II) was explained. • Potential bonding modes and adsorption sites of the two metal ions were proposed. [ABSTRACT FROM AUTHOR]