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[Display omitted] • H 3 PO 4 co-hydrothermal carbonization improved surface area and functional groups. • HC-5P showed highest adsorption and photocatalytic activity for NOR. • The adsorption and photocatalytic degradation mechanisms were proposed. • H 3 PO 4 co-hydrothermal carbonization is a promising way to prepare hydrochar photocatalyst. Hydrochars have been widely applied in removing pollutants from aqueous solutions. In this study, hydrochars synthesized by H 3 PO 4 -assisted hydrothermal carbonization (HC-xPs) were used to remove norfloxacin (NOR) from water through synergistic adsorption and photodegradation. HC-xPs showed the morphology of carbon microspheres with an average diameter of 0.3 μm. The specific surface area of the hydrochar carbonized with 5 mol/L H 3 PO 4 (HC-5P) was 11.2 times higher than that of the pristine hydrochar (HC). Furthermore, phosphorus-containing functional groups were introduced to HC-5P, beneficial to its adsorption of NOR. The highest NOR adsorption was achieved on HC-5P with the maximum Langmuir capacity of 69.1 mg g−1, owing to multiple mechanisms including electrostatic effects, π-π interactions, hydrophobic interactions, and hydrogen bonding. Compared with HC, HC-5P also demonstrated increased visible light absorption capacity. The first-order rate constant of HC-5P on combined adsorption and photodegradation of NOR was 12.0 times of HC. The photodegradation intermediates were identified by HPLC-MS to understand NOR degradation pathways. This work can be extended to the preparation of low-cost and highly efficient hydrochars for adsorption and photodegradation of pollutants in water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrochars were prepared from bamboo, cornstalk, and pine. • Bamboo hydrochar had good adsorption and photoreduction ability for Cr(VI) removal. • Possible mechanism for adsorption and photoreduction was elucidated. Photoreduction is recognized as a desirable treatment method for hexavalent chromium Cr(VI) because of the advantages of high efficiency, energy-saving, and environmentally friendly. Herein, three kinds of hydrochars were synthesized by one-step hydrothermal carbonization of agricultural and forestry residuals for synergistic adsorption and photoreduction of Cr(VI). All of them showed relatively strong adsorption capability to Cr(VI). Without illumination, the maximum adsorption capacities of bamboo hydrochar (BHC), cornstalk hydrochar (CHC), and pine wood hydrochar (PHC) were 177.0, 164.2, and 156.5 mg/g, respectively. Moreover, the hydrochars also had excellent photocatalytic properties as indicated by various characterization techniques. Under light irradiation, they created synergistic effects between adsorption and photoreduction to effectively remove Cr(VI) under various conditions. The synergistic removal of Cr(VI) by adsorption and photoreduction in ultrapure water, tap water, and lake water on BHC all reached almost 100% in 40 min. Besides, the photoreduction of Cr(VI) was almost unaffected with various coexisting ions (Cl-, SO 4 2-, PO 4 3-), and the removal rate of Cr(VI) remained above 90% within 60 min after 5 runs of synergistic adsorption-photoreduction. The photocatalytic mechanism suggests that the BHC had suitable band energies which can reduce Cr(VI) to Cr(III) by photo-induced electron. Findings of this study demonstrate that hydrochar is a promising dual-functional material for the treatment of Cr(VI) contaminated water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bi 2 O 2 CO 3 /biochar nanocomposites were firstly synthesized and reported. • Bi 2 O 2 CO 3 /biochar had good adsorption and photocatalytic activity for tetracycline. • Biochar facilitated the separation of photo-induced carriers in the composites. Adsorption and photodegradation are two widely studied wastewater treatment technologies. In this work, we have firstly prepared the bismuth oxycarbonate (Bi 2 O 2 CO 3) and biochar nanocomposites for synergistic adsorption-photodegradation of tetracycline (TC). It was found that Bi 2 O 2 CO 3 and biochar composites exhibited stronger adsorption capacity and photocatalytic activity compared to Bi 2 O 2 CO 3. Among them, Bi 2 O 2 CO 3 /2.5 wt% biochar possessed the highest adsorption capacity for TC (173.0 mg/L) and the best combined removal rate of TC (84.7 %) in 60 min by adsorption and photodegradation, which were 1.9 times and 1.5 times that of Bi 2 O 2 CO 3 , respectively. The biochar in the composite increased the specific surface area, promoted the adsorption of TC, facilitated charge transfer capability, thereby enhanced the photocatalytic activity of composites. The effects of experimental parameters (temperature, co-existing ions, and initial pH) on TC degradation were examined. Electron spin resonance (ESR) and trapping experiments of free radical confirmed that 1O 2 , •O 2 − and h+ were the main species in photocatalytic degradation. The potential degradation pathways were proposed based on liquid chromatograph mass spectrometer (LC-MS) test of the intermediates of TC degradation. It is hoped that this work not only represents the significantly importance of biochar in photocatalytic wastewater treatment, but also promotes further interests in design synergistic adsorption-photodegradation materials. [ABSTRACT FROM AUTHOR]

Improving the adsorption ability of layered double hydroxide (LDH) has been considered as a promising strategy to promote its photodegradation of aqueous pollutants. In this work, nickel-aluminium layered double hydroxides (NiAl-LDH)/biochar nanocomposites were prepared using a simple coprecipitation method, and then applied in synergistic adsorption-photodegradation of tetracycline (TC) in aqueous solutions. In addition, the governing TC removal mechanisms by the nanocomposites were revealed. All NiAl-LDH/BC samples showed strong adsorption and photodegradation of TC. The Langmuir maximum TC adsorption capacity of optimized NiAl-LDH/BC-0.5 reached 124.2 mg/g, which was much better than that of NiAl-LDH (56.1 mg/g) and biochar (11.1 mg/g). Besides, TC photodegradation rate constant of NiAl/BC - 0.5 was 3.6 and 4.4 times of that of NiAl-LDH and BC, respectively. The NiAl/BC - 0.5 exhibited the maximum TC adsorption-photodegradation efficiency 94.4% in 90 min compared to NiAl-LDH (73.7%) and BC (48.2%). The rate constant of modified Elovich kinetic model for synergistic adsorption and photodegradation on NiAl/BC-0.5 (9.477 min−1) was the highest among the composites. The NiAl-LDH/BC had significantly larger BET surface areas than NiAl-LDH and BC. The step scheme (S-scheme) heterostructures were constructed on the interface of BC and NiAl-LDH in nanocomposites, which facilitated the transfer of photo-induced charges. This work demonstrates that combination of NiAl-LDH and biochar can create synergy for TC adsorption-photodegradation, which is a promising and green strategy. [Display omitted] • NiAl-LDH/BC composites were prepared through simple coprecipitation. • NiAl-LDH/BC composites showed improved physicochemical and catalytic properties. • S-scheme heterostructure was constructed on the interface of BC and NiAl-LDH. • NiAl-LDH/BC effectively removed TC by synergistic adsorption and photodegradation. [ABSTRACT FROM AUTHOR]

The adsorption of reactants is highly correlated with photocatalysis. Improving the adsorption ability of photocatalyst may realize highly efficient removal performance. In this work, Bi 2 MoO 6 and bamboo-derived biochar composite was developed by a facile ball milling method. The adsorption and photodegradation abilities of the composites were evaluated by removing methylene blue (MB), which is a most commonly used aromatic-cationic dye. The maximum adsorption capacity of MB on the optimized 20 % Bi 2 MoO 6 /biochar sample was 160.6 mg/g, and the synergistic adsorption-photocatalytic removal efficiency of MB reached 93.3 % within 30 min, which were superior to Bi 2 MoO 6 (13.3 mg/g, 31.6 %) and biochar (127.7 mg/g, 69.8 %). Compared to Bi 2 MoO 6 , the Bi 2 MoO 6 /biochar composites showed decreased bandgap and enhanced charge separation efficiency. The strong interfacial interactions between Bi 2 MoO 6 and biochar in composites facilitated the photo-induced electrons transfer. Furthermore, the photodegradation efficiency enhanced along with the adsorption efficiency while pH value increased, which further proves the synergy between adsorption and photodegradation. Noticeably, the 20 % Bi 2 MoO 6 /biochar can completely remove MB at pH between 3 and 11. This work proves Bi 2 MoO 6 modified biochar prepared by ball milling is a promising material for synergistic adsorption and photodegradation removal of organic pollutants. [Display omitted] • The optimized 20 % BMO/BC had the maximum adsorption capacity of 160.6 mg/g. • The 20 % BMO/BC showed high MB removal efficiency under light (99.7 %, 60 min). • Removal kinetics were applied to analyze the processes under light or dark. • Synergistic adsorption and photodegradation removal mechanism was elucidated. • Biochar promoted photo-inducted charges transfer in composites. [ABSTRACT FROM AUTHOR]

In this paper, bismuth oxybromide (BiOBr)/biochar composites were synthesized by a facile ball milling method for synergistic adsorption and photodegradation of Reactive red 120 (RR120). The characterizations show that ball milling changed the degree of crystallization, increased the surface area, and promoted the charge transfer ability of biochar. The 70% BiOBr/BC composite showed the best removal efficiency for RR120 removal with or without light illumination, which proves its enhanced removal ability by adsorption and photodegradation. The biochar is served as a support of BiOBr for preventing its aggregation and a transporter of charges for promoting the separation of photo-induced carriers in composites. BiOBr can release the adsorption sites on the surface of composites by degradation, which facilitated the RR120 removal and regenerated the photocatalyst for reusing. The strong interactions between BiOBr and biochar in composites resulted from ball milling were beneficial for the charge transfer and synergistic removal of adsorption and degradation. Findings of this work indicate that ball milling method is an effective method to prepare highly efficient biochar-based composites for RR120 removal through synergistic adsorption and photodegradation. [Display omitted] • BiOBr/biochar composites were firstly synthesized by ball milling method. • Biochar increased the surface area and promoted charge transfer in composites. • There were strong interactions between BiOBr and biochar after ball milling. • Synergy between adsorption and photodegradation in BiOBr/biochar is elucidated. [ABSTRACT FROM AUTHOR]