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[Display omitted] • H 2 O 2 -modified ball-milled biochar were synthesized to adsorb methylene blue (MB). • H 2 O 2 modification increased the oxygen-containing functional groups of biochar. • H 2 O 2 modification improved the adsorption capacity of biochar to MB. In this work, hickory chip biochars developed at distinctive pyrolysis temperatures were ball milled (BMHC) and then post-modified with a 10% hydrogen peroxide (H 2 O 2) solution to obtain a set of novel sorbents (BMHC-H 2 O 2). The specific surface area (SSA) was dramatically increased after ball-milling while the hydroxyl and carboxyl groups on the surface of the biochars were further increased through H 2 O 2 modification. Additionally, thermal stability of the biochar treated with ball-milling was not greatly reduced by H 2 O 2 modification and hydrodynamic radius was decreased. Ball milling enhanced the adsorption efficiency to methylene blue (MB) by the biochar, and this ability was further increased by H 2 O 2 modification, because of the increasing in oxygen-containing functional groups (OCFG) to interact with MB. The rate of MB adsorption to BMHC-H 2 O 2 was faster than that of BMHC, reaching equilibrium after about 6 h. Among adsorbents tested, the 450 °C BMHC-H 2 O 2 had the greatest MB adsorption capacity (310 mg g−1). [ABSTRACT FROM AUTHOR]

[Display omitted] • Wheat straw hydrochar modified with 0.2 M KMnO 4 obtained optimal results. • KMnO 4 modification loaded MnOx microparticles on hydrochar surface. • Oxygen-containing surface functional groups increased after modification. • KMnO 4 modification enhanced adsorption of Pb(II), Cd(II), Cu(II) by > 10 times. Hydrochars formed by hydrothermal carbonization of hickory wood, bamboo, and wheat straw at 200 °C were modified by potassium permanganate (KMnO 4) for the sorption of Pb(II), Cd(II), and Cu(II). The wheat straw hydrochar (WSHyC) modified with 0.2 M KMnO 4 resulted in the most promising adsorbent (WSHyC-0.2KMnO 4). Characterization of WSHyC and WSHyC-0.2KMnO 4 revealed that the modified hydrochar features large specific surface area, rich of surface oxygenic functional groups (OCFG), and a significant amount of MnOx micro-particles. Batch adsorption experiments indicated that the adsorption rate by WSHyC-0.2KMnO 4 was faster than for WSHyC, attaining equilibrium after around 5 h. The optimum adsorption capacity (Langmuir) of Pb(II), Cd(II), and Cu(II) by WSHyC-0.2KMnO 4 was 189.24, 29.06 and 32.68 mg/g, respectively, 12 ∼ 17 times greater than by WSHyC. The significantly enhanced heavy metal adsorption can be attributable to the increased OCFG and MnOx microparticles on the surface, thereby promoting ion exchange, electrostatic interactions, and complexation mechanisms. [ABSTRACT FROM AUTHOR]

A novel biochar composite was fabricated via the pyrolysis of distillers grains treated phosphogypsum for phosphate removal from water. Batch adsorption experiments were performed on the adsorption characteristics of phosphate. Effects of pyrolysis temperature, solution pH, the dosage of adsorbent, ambient temperature on phosphate adsorption were also investigated. The results demonstrated that the optimum initial solution pH for phosphate adsorption was 6.0, and high pyrolysis temperature was favorable for phosphate adsorption. The optimal dosage of biochar was 1.25 g L−1. A pseudo-second-order kinetic model can well explain the adsorption kinetics, indicative of the energetically heterogeneous solid surface of the composite. The maximum phosphate adsorption capacity of the phosphogypsum modified biochar obtained from Langmuir isotherm reached 102.4 mg g−1 which was almost five times that of distillers grains biochar alone (21.5 mg g−1). The mechanism is mainly attributed to electrostatic adsorption, surface precipitation and ligand exchange. The ideal adsorption performance indicated that biochar supported phosphogypsum can be used as high-quality adsorbent for phosphate removal in wastewater treatment. • A novel biochar composite was synthesized for phosphate adsorption. • The maximum phosphate adsorption capacity reached 102.4 mg g−1. • The adsorption mechanism is mainly attributed to electrostatic adsorption, surface precipitation and ligand exchange. • The composite can be used as high-quality adsorbent for phosphate removal. [ABSTRACT FROM AUTHOR]

• Adsorption kinetic rate of dye on g-C 3 N 4 was faster than those of photodegradation processes. • Surface photodegradation kinetic rate of dye adsorbed on g-C 3 N 4 was faster than that in solution. • Synergy between adsorption and photodegradation of dye by g-C 3 N 4 was confirmed and elucidated. • Modified Elovich model was the best to simulate the integrated adsorption and photodegradation kinetics. The synergy between adsorption and photocatalysis has been well recognized in contaminant photodegradation; however, the governing mechanism is still not clear. The main objective of this work is to understand the kinetic processes of synergic adsorption-photocatalysis of graphitic carbon nitrate (g-C 3 N 4), a visible light responsive photocatalyst with a planar graphitic-like structure, in organic contaminant removal. An anionic dye Reactive Red 120 (RR120), which has six sulphonate groups and a complex aromatic molecular structure, was selected as a model contaminant compound. A range of experiments were conducted to determine the kinetics of adsorption, photodegradation, and the integrated process. Various kinetic models were used to simulate and interpret the experimental data and thus to unveil the governing mechanisms. The integrated adsorption and photodegradation of the dye by g-C 3 N 4 was mainly controlled by: 1) adsorption of dye onto g-C 3 N 4 surface, 2) photodegradation of dye in bulk solution, and 3) photodegradation of adsorbed dye on g-C 3 N 4 surface. Both experimental and modeling results showed that the adsorption kinetic rate (3.37 min−1) was faster than the photodegradation kinetic rates. In addition, the surface photodegradation kinetic rate of adsorbed dye (0.149 min−1) was faster than that in solution (0.005 min−1). Adsorption process thus can promote the photodegradation of contaminants by g-C 3 N 4. On the other hand, photodegradation of dye-laden g-C 3 N 4 regenerated its adsorption capacity for multiple times, suggesting photocatalysis process can also promote the adsorption of contaminates on g-C 3 N 4. [ABSTRACT FROM AUTHOR]