Search

• Solvothermal synthesis of pyridinium functionalized chitosan. • High efficiency of functionalized chitosan for methyl orange and Cr(VI) sorption. • A key role of pyridinium plays in adsorption. • Stable sorption and desorption properties for 5 successive cycles. A pyridinium functionalization chitosan (PCS) at high yield was facilely and solvothermally obtained from reactions of chitosan with N-2,4-dinitrophenyl-pyridinium chloride. The morphology and physical–chemical properties of PCS were tested with various techniques. Its sorption behaviors towards methyl orange (MO) and Cr(VI) were systematically investigated. Pseudo-second-order kinetic and Langmuir equations well fitted the sorption kinetics and isotherms, respectively. Thermodynamics analyses revealed the spontaneous and endothermic sorption of these two contaminants. PCS exhibited high sorption capacity of 1649.30 mg·g−1 MO and 200.46 mg·g−1 Cr(VI) at 308 K. The superior sorption performance of PCS over MO is ascribed to ion exchange, intermolecular hydrogen bond, and electrostatic and π-π interactions, while sorption of PCS over Cr(VI) is mainly driven by electrostatic forces, reduction and ion exchange. Moreover, the PCS exceeded 95 % of its original capacities during five cycles. This high sorption capacities and high reusability make PCS an excellent sorbent candidate towards anionic contaminants. [ABSTRACT FROM AUTHOR]

Highlights • The protonated amine modified hydrochar was synthesized for anionic dye removal. • The protonated amine groups play a key role on sorption of MO by PAMH. • The electrostatic interaction is the main mechanism. • The modified hydrochar can remove efficiently MO from aqueous solution. Abstract The protonated amine modified hydrochar (PAMH) was synthesized by etherification, amination and protonated reaction with hydrochar, which was enriched with abundant protonated amine for methyl orange (MO) removal. PAMH was characterized by elemental analysis, scanning electron microscopy, nitrogen adsorption-desorption measurement, zeta potential and Fourier transform infrared. The sorption of MO from aqueous solution by PAMH was investigated by batch experiments. The results showed that sorption of MO was significantly influenced by the initial concentration of MO, temperature, contact time and ionic strength, while hardly affected by pH values ranging from 4 to 11. The pseudo-second-order and Langmuir equations were able to depict sorption kinetics and sorption isotherms, respectively. Thermodynamic analysis indicated that the sorption behavior was thermopositive and spontaneous. The maximum theoretical uptake computed by the Langmuir equation was 909.09 mg·g−1 at 303 K, which suggested that PAMH was an effective sorbent to eliminate anionic dye from aqueous solution. [ABSTRACT FROM AUTHOR]

• The novel magnetic activated biochar nanocomposites were first time prepared using wakame. • Loading nickel on the surface of wakame biochar is conducive to its recycling. • The adsorption process is a spontaneous endothermic process. • At 293 K, the maximum adsorption capacity of MB is 479.49 mg/g. In this work, magnetic wakame biochar nanocomposites for the first time had been synthesized to investigate their adsorption to methylene blue dye. As-prepared magnetic biochar samples were obtained by the impregnation method to load nickel on wakame biochar via one-step carbonization with activation agent KOH at 800 °C. The prepared samples were characterized by BET, XRD, FTIR, Raman, SEM, TEM and so on. The results exhibited that the maximum adsorption capacity of BW(Ni)0.5 to methylene blue could reach 479.49 mg/g at 20 °C. The adsorption behavior was more suitable for Langmuir isotherm equation and the kinetic data were most consistent with the pseudo second-order model. And also, the adsorption reaction was a spontaneous and endothermic process. After five cycles, it was found that BW(Ni)0.5 had a high adsorption capacity for methylene blue (117.58 mg/g). This study demonstrated that wakame biochar could have great potential in dye wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Acrylate-modified hydrochar with excellent adsorption properties was prepared easily. • The removal amounts of Pb(II) and methylene blue exceed 291.96 and 1014.96 mg/g. • Acrylate plays a key role in the adsorption process. • The acrylate content was more influential on adsorption than specific surface area. • The structure of hydrochar significantly affects its functional modification. Hydrochars are promising sorbents for wastewater treatment. Herein, two acrylate-modified hydrochars (AMHC 1 and AMHC 2) were obtained by grafting acrylic acid on the surface of two hydrochars (MHC 1 and MHC 2 hydrothermally carbonized in water and acidic medium respectively) with free radical polymerization. Characterizations show that MHC 2 is more prone to free radical polymerization than MHC 1 does, and has higher carboxylate content after modification. The adsorption amounts of AMHC 2 over methylene blue (MB) and Pb(II) are much higher than those of AMHC 1. Pseudo-second-order kinetic and Langmuir isotherm equations well fit the Pb(II) and MB sorption data of AMHC 2. The Pb(II) adsorptive mechanism is mainly inner-surface complexation accompanied by ion exchange and cation-π interaction. MB adsorption involves ion exchange, electrostatic interaction, H-bonding and π-π interaction. Hence, the one-step modification method of free radical polymerization under alkaline condition has great potential for preparing carboxylate-modified hydrochars to adsorb cationic pollutants. [ABSTRACT FROM AUTHOR]

[Display omitted] • IFHC was prepared from one-step solvent-free radical copolymerization. • IFHC has rich carboxylate and effectively adsorbs cationic contaminants. • The sorption amounts of Pb(II) and MB exceed 291 and 1036 mg/g respectively. • Carboxylate plays a key role in the removal of cationic contaminants. • Solvent-free radical copolymerization can effectively functionalize hydrochar. An itaconate-functionalized hydrochar (IFHC) was prepared from one-step solvent-free radical copolymerization of bamboo hydrochar, itaconic acid, ammonium persulphate and sodium hydroxide in solvent-free environment, and was employed to absorb methylene blue (MB) and Pb(II) from wastewater. Characterizations show IFHC has rich carboxylate and tends to adsorb cationic contaminants. The largest adsorbed quantities of MB and Pb(II) by IFHC are up to 1036 and 291.8 mg·g−1 at 298 K respectively as per the Langmuir isotherm. Sorption of MB and Pb(II) onto IFHC can be expressed well by Langmuir isotherm and pseudo-2nd-order kinetics equations. The high sorption performance depends on the rich carboxylate, which can adsorb MB/Pb(II) through an electrostatic interaction/inner-surface complexation mechanism. The sorptive capacity of regenerated IFHC decreased below 10% after 5 desorption-resorption cycles. Thus, the solvent-free free radical copolymerization is an environmentally-friendly strategy to synthesize novel efficient sorbents that can clean cationic contaminants from wastewater. [ABSTRACT FROM AUTHOR]

• Fe 3 O 4 -loaded hydrochar was prepared by HTC and precipitation. • FeCl 3 plays at least two roles as a catalyst and an oxidant in HTC. • Electrostatic interaction was the primary mechanism of MB sorption by HC-Fe 3 O 4. • Fe 3 O 4 -loaded hydrochar can be stably recycled for at least 5 consecutive cycles. • Adsorption follows Langmuir isotherm and pseudo-second-order kinetics. Highly efficient and cheap magnetic materials have application prospects in wastewater treatment. Herein, Fe 3 O 4 -loaded hydrochar (HC-Fe 3 O 4) was obtained from hydrothermal carbonization (HTC) of bamboo with FeCl 3 and then added with FeCl 3 to form a magnetic sorbent via simple precipitation. The HC-Fe 3 O 4 was characterized with various instruments. The characterizations show FeCl 3 plays at least two roles as a catalyst and an oxidant in HTC. The specific surface area of hydrochar enlarged from 39.9731 to 60.9887 m2·g−1 after the addition of FeCl 3 during HTC, which showed FeCl 3 acted as a catalyst in HTC. XRD indicated Fe 3 O 4 was formed by the structure of HC-Fe 3 O 4 , which indicated Fe(III) was reduced to Fe(II) during HTC. Sorption of methylene blue (MB) onto HC-Fe 3 O 4 was better fitted by the Langmuir isotherm and pseudo-second-order kinetic models. Sorption is a spontaneous thermodynamic endothermic process and HC-Fe 3 O 4 is easily separated by an applied magnetic field and reused. [ABSTRACT FROM AUTHOR]