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A two-stage deep eutectic solvents (DESs) treatment was shown to be an effective method for improving the utilization of certain DESs, and the specific order of pretreatment, such as malic acid/proline (MP) or choline chloride/oxalic acid (CO) during the first stage and choline chloride/urea (CU) during the second stage, resulted in better performance for enhancing the sugar yield due to the synergistic effect of the two DESs on biomass fractionation. Moreover, the presence of water during these processes could balance the loss of components by tuning the pretreatment severity, thus ensuring higher sugar yields. By eliminating the washing step after the first stage treatment, enhanced cellulose recovery and glucose yield were achieved for the CO-CU pretreatment in the presence of 5% water, and a simpler process was established with a glucose yield of 90.2% after a 3-h treatment at 100 °C. [ABSTRACT FROM AUTHOR]

The bioethanol fermentation of pretreated corncob was investigated using Spathaspora passalidarum U1-58, which simultaneously utilizes glucose and xylose for high-efficiency ethanol production. Two approaches, namely, separate hydrolysis and co-fermentation (SHCF) and simultaneous saccharification and co-fermentation (SSCF), were optimized to test the ethanol fermentation potential of U1-58. The highest ethanol titer of 42.46 g/L and yield of 72.12% were acquired in SHCF, whereas 53.24 g/L ethanol and yield of 75.35% were obtained in SSCF at solid-to-liquid ratio of 1:5 (w/v). Approximately 86.20% of cellulose and 82.99% of hemicellulose were consumed in SSCF after 96 h, and at least 10.49 g/L ethanol was produced from hemicellulose, which corresponded to 37.59% of the theoretical yield. Compared with the published cellulosic ethanol fermentation cases, the present work presented high ethanol titer and yield, and cellulose and hemicellulose could be efficiently utilized for ethanol production. [ABSTRACT FROM AUTHOR]

• 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]

[Display omitted] • Functionalized hydrochar was prepared by free radical post-synthetic modification. • Hydrochar with − N+H 2 R groups exhibited high adsorption capacity towards Cr(VI). • •Nitrogen-containing groups in hydrochar play multiple roles in adsorption procedure. Chemical modification on hydrochars can significantly improve their ability of removing heavy metal ions from wastewater, but so far no research has focused on the chemical modification through free radical reaction. In this work, a cation functionalized hydrochar (CFHC) bearing − N+H 2 R was synthesized by grafting-polymerization of glycidyl methacrylate (GMA) onto bamboo hydrochar under initiation by benzoyl peroxide, followed by the amination with the introduced epoxy group and diethylenetriamine and a subsequent hydrochloric acid treatment. The resulted CFHC exhibited a superior removal capacity of 424.09 mg·g−1 for Cr(VI), and the highest sorption occurred at pH of 2. Combining a series of characterizations and tests, it was concluded that the sorption conformed to the pseudo-second-order and Freundlich equations, indicating a multilayer chemisorption process that mainly driven by electrostatic reaction, reduction, and surface complexation. This research proved that a free radical polymerization treatment could effectively transform hydrochars into super adsorbents for wastewater treatment. [ABSTRACT FROM AUTHOR]

Abstract: Limited filamentous bulking caused by low dissolved oxygen (DO) was proposed to establish a low energy consumption wastewater treatment system. This method for energy saving was derived from two full-scale field observations, which showed pollutants removal would be enhanced and energy consumption could be reduced by atleast 10% using limited filamentous bulking. Furthermore, preliminary investigation including the abundance evaluation and the identification of filamentous bacteria demonstrated that the limited filamentous bulking could be repeated steadily in a lab-scale anoxic–oxic reactor fed with domestic wastewater. The sludge loss did not occur in the secondary clarifier, while COD and total nitrogen removal efficiencies were improved by controlling DO for optimal filamentous bacterial population. Suspended solids in effluent were negligible and turbidity was lower than 2 NTU, which were distinctly lower than those under no bulking. Theoretical and experimental results indicated the aeration consumption could be saved by the application of limited filamentous bulking. [Copyright &y& Elsevier]

• A novel strategy was developed to prepare nitrogen rich biochar. • APBC has high affinity and strong sorption ability towards Pb(II). • APBC contains abundant nitrogen and oxygen-containing groups. • Sorption of Pb(II) is mainly dominant by inner–sphere surface complexation. Biochar was prepared by torrefaction of ammonium persulphate pretreated bamboo (labeled as APBC) and applied into elimination of Pb(II) from water solutions. APBC was characterized by N 2 adsorption–desorption isotherms, elemental and Zeta potential analyses, SEM-EDS, XPS, and FTIR. Abundant N- and O-containing groups appeared atop APBC. Batch sorption assays revealed that APBC had high affinity and strong sorption ability towards Pb(II). The high Pb(II) adsorbing ability was attributed to the high contents of N- and O-containing functional groups of APBC. The adsorption mechanism mainly occurred by inner–sphere surface complexation. Hence, torrefaction of ammonium persulphate pretreated bamboo is a promising strategy for producing efficient biochar that is applicable for industrial wastewater treatment. [ABSTRACT FROM AUTHOR]

Highlights • ACHC with abundant amino, hydroxyl and carboxylate groups was prepared successfully. • ACHC can remove efficiently and rapidly MB and Cu(II) from aqueous solution. • The surface chelation was mainly contribute to Cu(II) adsorption. • π-π interaction, hydrogen bond and electrostatic attraction dominated MB adsorption. Abstract The polyaminocarboxylated modified hydrochar (ACHC) was synthesized to introduce abundant amino, hydroxyl and carboxylate multifunctional groups onto the surface of hydrochar by etherification, amination and carboxylated reaction. The ACHC was systematically characterized and used to evaluate adsorption properties of Cu(II) and methylene blue (MB) by batch sorption tests. The adsorption process toward Cu(II) and MB by ACHC obeyed the pseudo-second-order kinetic model and Langmuir model. Characteristic analysis indicated the surface chelation was mainly contribute to Cu(II) adsorption by large amounts of amino and carboxylate groups while π-π interaction, hydrogen bonding and electrostatic attraction dominated MB adsorption. The maximum adsorption capacities of ACHC were 140.65 and 1238.66 mg·g−1 for Cu(II) and MB at 303 K, respectively. Approximately 97% of the adsorptive uptakes for two pollutants were removed within merely 5 min for kinetic experiment. Competitive adsorption of Cu(II) and MB, and treatment of electroplating wastewater by ACHC were also investigated. [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]

[Display omitted] • Two biochars were prepared from APS/KPS-pretreated bamboo. • Cation types in persulfate impact physicochemical properties of biochar. • The KPS-pretreated bamboo-derived biochar has a higher adsorptive capacity for MB. • The discrepancy in adsorption capacity of two biochar for MB was analyzed. • Electrostatic action is the main adsorption mechanism for MB onto biochars. The adsorption behaviors of biochar are largely impacted by biomass feedstock. In this study, two biochars were prepared from torrefaction of ammonium persulfate- and potassium persulfate-pretreated bamboo and then activated by cold alkali, which are named as ASBC and KSBC, respectively. The two biochars were characterized by different instruments, and their adsorption properties over cationic methylene blue (MB) were compared. The type of persulfates little affected the specific surface areas, but significantly impacted O (29.54 % vs. 35.113 %) and N (12.13 % vs. 3.74 %) contents, functional groups, and zeta potentials of biochars. MB adsorption onto ASBC/KSBC is a single-layer chemical endothermic process and ASBC/KSBC exhibit high adsorption capacity over MB (475/881 mg·g−1) at 303 K. Obviously, the sorption capacity of MB onto KSBC much surpasses that of MB onto ASBC. These results indicate biomass pre-treatment is a cheap and convenient method to prepare biochars with unique physicochemical and adsorptive properties. [ABSTRACT FROM AUTHOR]

• N-doped hydrochar was synthesized by one-step hydrothermal reaction. • Cr(VI) adsorption capacity of hydrochar was enhanced by N-doping. • NH 4 Cl acts as a catalyst and a nitrogen source in preparation of N-doped hydrochar. • N-groups can adsorb Cr(VI) by electrostatic interaction and reduce Cr(VI) to Cr(III). N-doped biochar can effectively eliminate toxic Cr(VI). Here, N-doped hydrochar (NHC) was successfully synthesized by one-pot hydrothermal carbonization (HTC) of NH 4 Cl and bamboo, and employed to adsorb Cr(VI). The specific surface area, pore volume, and carbon and nitrogen contents of NHC all increase compared with the undoped hydrochar (HC). NH 4 Cl acts as a cheap nitrogen source to enhance the nitrogen content of hydrochar and as an acid catalyst to accelerate hydrochar carbonization. Adsorption experiments show NHC has higher adsorption capacity than HC for Cr(VI). XPS and FTIR imply the dominant mechanisms of adsorbing Cr(VI) onto two hydrochars are electrostatic attraction, reduction and complexation, but the contributions of surface functional groups in two hydrochars for elimination of Cr(VI) differ. The doped nitrogen in NHC is pivotal in adsorbing and reducing Cr(VI). Hence, NHC prepared from bamboo and NH 4 Cl by one-step HTC is a cheap and efficient adsorbent to eliminate aqueous Cr(VI). [ABSTRACT FROM AUTHOR]

• Co-HTC of PVC and bamboo was employed to prepare high-efficiency adsorbent. • The contents of hydroxyl and carboxyl groups of hydrochar increased during Co-HTC. • Adsorption capacity of MB on hydrochar produced by addition of PVC increased significantly. • Electrostatic and hydrogen-bonding interactions are the main mechanisms. Polyvinyl chloride (PVC) was blended into bamboo powder during co-hydrothermal carbonization (Co-HTC) to understand the effects on the physicochemical properties and adsorbing ability of hydrochar. The properties of hydrochar were characterized by Zeta potential, elemental analyses, BET, FTIR, XPS, Boehm titration and SEM. The addition of PVC into bamboo in Co-HTC decreased the BET area, and pore volume and radius of hydrochar, but increased the contents of surface hydroxyl and carboxyl groups. The adsorption ability of hydrochar produced by addition of PVC at 473 K over methylene blue (MB) increased significantly. The main adsorption mechanism was electrostatic attraction by –N(CH 3) 2 + of MB and carboxylate of hydrochar, and hydrogen-bonding interaction through N atom of phenothiazine in MB and C–OH of hydrochar. Thus, Co-HTC offers a facile, green and economical alternative for conversion of waste into high-value adsorbents. [ABSTRACT FROM AUTHOR]

• Fe 3 O 4 -AMHC can be easily separated from water using an external magnet. • Fe 3 O 4 -AMHC can selectively adsorb methylene blue at pH 11.0 or methyl orange at pH 5.0. • Electrostatic interaction plays a key role in the selective adsorption of dyes. • Fe 3 O 4 -PAMH can be reused in the dye adsorption/desorption cycles. Fe 3 O 4 -loaded protonated amine-modified hydrochar (Fe 3 O 4 -PAMH) was successfully prepared and characterized by scan electron microscopy equipped with energy-dispersion X-ray spectroscopy, zeta potential analysis, vibration sample magnetometry, Fourier transform infrared and X-ray photoelectron spectroscopies, Brunauer-Emmett-Teller measurement, and X - ray diffraction. Adsorption properties of Fe 3 O 4 -PAMH to negatively-charged methyl orange (MO) or positively-charged methylene blue (MB) in one- or two-component systems were evaluated. The Fe 3 O 4 -PAMH selectively adsorbed MO and MB at pH 5 and 11, respectively. The maximum MO and MB uptake capacities of Fe 3 O 4 -AMHC were 202.02 mg/g (pH 5.0) and 148.84 mg/g (pH 11) respectively. The Fe 3 O 4 -PAMH can be reused with simple pH management in adsorption-desorption cycles. The MB and MO adsorption abilities on Fe 3 O 4 -PAMH were maintained above 99% and 75% for five consecutive recycles, respectively. Thus, Fe 3 O 4 -PAMH shows powerful potential in efficiently and selectively adsorbing anionic or cationic dyes from mixed wastewater. [ABSTRACT FROM AUTHOR]

• A one-step pyrolysis/activation method was used to prepare wakame biochar (AWBM). • AWBM has abundant mesopores with a high specific surface area (1156.25 m2/g). • At 293 K, the adsorption of MG using AWBM can reach 4066.96 mg/g. • The adsorption of dyes using AWBM contain physical and chemical adsorption. In this study, an activated wakame biochar material (AWBM) was prepared by a one-step calcination and activation method, whose adsorption performances for methylene blue (MB), Rhodamine B (RB) and malachite green (MG) were also analyzed. The results showed AWBM was a mesoporous fluffy structure material with a higher specific surface (1156.25 m2/g), exhibiting superior adsorption capacities for MB (841.64 mg/g), RB (533.77 mg/g) and MG (4066.96 mg/g), respectively. In addition, FT-IR analysis showed that AWBM possessed abundant active groups (such as –OH, –CO and –CH), further enhancing the adsorption efficiencies. The Langmuir model could better fit the three dyes adsorption isotherms process using AWBM, and the Pseudo-second-order model could better describe the adsorption kinetic experimental data. The thermodynamic analysis showed that the three dyes adsorption using AWBM was spontaneous endothermic reaction. This study suggests AWBM has enormous potential in the application of removing organic dyes from wastewater. [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]

Graphical abstract Highlights • A porous K-CMSP was prepared with mussel shell powder and activated by K 2 CO 3. • K-CMSP modified with L-ARG had rendered a positively charged surface. • Immobilized microalgae could survive for more than 60 days. • Immobilized microalgae could revive to normal growth level within 10 days. • The removal rate of N and P by immobilized microalgae were 95.0% and 88.63%. Abstract In this work, calcined mussel shell powder (CMSP) was activated by K 2 CO 3 (K-CMSP), and this porous K-CMSP surface was modified by L-arginine (L-ARG) to render porous biomass a positively charged surface, which was innovatively utilized as a carrier to immobilize microalgae by adsorption via electrostatic interactions. The pore and the surface structures of CMSP and K-CMSP were characterized by XRD, FTIR, BET and SEM. The surface morphology of immobilized microalgae was visualized via using inverted optical microscope and SEM. It was found that microalgae could survive for 60 days, and the loss rate of chlorophyll-a preserved at −24 °C was the lowest, 44.73%. The microalgae could revive to normal growth level within 10 days and the cell content of microalgae was the highest at 25 °C, 2.8022 × 106 cell/mL. At 25 °C, the highest removal rate of N and P was obtained about 95.0% and 88.63%, respectively. [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]