Search

Graphical abstract Highlights • Effect of hydrothermal condition on exfoliating CNQDs was examined. • O atoms are substituted onto the GCN sheets during HT treatment. • CNQD(180)12 has the highest capabilities in photocatalysis under LED (400 nm) • CQDs on GCN allow effective electrons transfer and delay PL decays. Abstract In this study, exfoliated g-C 3 N 4 (GCN) coupled carbon quantum dots (CNQDs) were prepared via one-pot hydrothermal (HT) treatment at various temperatures (100–200 °C) and in various amounts of time (0–20 h). Comprehensive characterization was conducted to study not only the chemical states, photo-optical properties, particle sizes, and crystal structures, but also the effect of these changes on the degradation of BPA. Photocatalytic degradation was conducted under near-visible LED as a low energy light source (0.128 W cm−3). The CNQD that were prepared at 180 °C for 12 h showed the highest degradation rate (3.6 × 10−2 min−1), which was 3.0 times higher than GCN. These improved photocatalytic activities corresponded to increases in the photo-reactive surface via exfoliation of GCN sheets, introduction of heteroatom oxygen onto GCN sheets, the addition of CQDs, and shortened bandgap. These characteristics allow for the effective transfer and separation of electrons. Nonetheless, the structural breakdown of the CNQD was observed when the HT time was longer than 12 h (180 °C). The defected sheets showed a detrimental effect towards photocatalytic degradation by trapping electrons, leading to shorter electron life times. [ABSTRACT FROM AUTHOR]

[Display omitted] • Floatable P-ZsZc was prepared by pre-seeding ZnO followed by hydrothermal treatment. • P-ZsZc shows an uplifted valence band and new covalent Zn-O-C bonds. • Combining ZnO with PU improves photo-corrosion by boosting the h+ mobility. • Scavenger experiments and ESR spin trap analysis revealed H 2 O 2 as the main ROS. • The P-ZsZc achieved up to ∼ 90% SMX removal in continuous flow experiments. A highly efficient rigid floatable photocatalyst was prepared by seeding ZnO in polyurethane (PU) and subsequent hydrothermal ZnO coating (P-ZsZc). Compared to pristine ZnO, granular P-ZsZc had an uplifted valence band (VB) and generated new covalent Zn-O-C bond between PU and ZnO, resulting in a significantly enhanced photocorrosion resistance by boosting the mobility of photoexcited holes. In addition, the VB of P-ZsZc was favorable for the in-situ oxygen evolution reaction (OER) and H 2 O 2 production. As a result, the P-ZsZc achieved ∼ 98% removal of sulfamethoxazole (SMX) within 2 h for 5 consecutive cycles. Moreover, the SMX removal rate and Zn(II) leaching remained at ∼ 0.036 min−1 and 0.17 mg L−1, respectively, even during the fifth cycle for 10 h. Furthermore, scavenger experiments and electron spin resonance (ESR) spin trap analysis revealed that the main photogenerated reactive oxygen species (ROS) was H 2 O 2. Floatable P-ZsZc showed constant SMX removal of ∼ 90% in continuous flow experiments (CFEs) for up to 10 h of operation. This study offers a new approach to prepare floatable rigid photocatalysts capable of in-situ oxygen and H 2 O 2 production to degrade organic pollutants. [ABSTRACT FROM AUTHOR]

Novel integration of adsorption followed by catalytic oxidation is expected to be more beneficial for higher Mn(II) removal performance. We prepared self-assembled 3D flower-like Mg(OH) 2 coated on granular-sized polyurethane (namely FMHP) via hydrothermal method at 120 °C under a facile synthesis route. The optimized material, FMHP prepared with 7 g MgO and 20 g polyurethane (FMH 0.35 P), achieved up to 351.2 mg g−1 Mn(II) removal capacity by Langmuir isotherm model. Besides, FMHP exhibited high Mn(II) removal in a wide range of NaCl concentration (0~0.1 M) and pH 2–9. Notably, through consecutive kinetics, BET, XPS, XRD, FESEM, and TEM analyses, it was found that the MnO x layer grows in-situ via ion exchange with Mg(II) on FMHP and further boosts the Mn(II) removal via catalytic oxidation during the Mn(II) removal process. Further, column experiments revealed that the FMH 0.35 P exhibited superior Mn(II) removal capacities up to 135.9 mg g−1 and highly compatible treatment costs ($0.062 m−3) compared to conventional chemical processes. The granular-sized FMH 0.35 P prepared by economic precursors and simple synthesis route revealed a high potential for Mn(II) containing water treatment due to its high removal capacities and easy operation. [Display omitted] • Self-assembled 3D flower-like Mg(OH) 2 coated on granular-sized PU was prepared. • FMH 0.35 P, achieved up to 351.2 mg g−1 Mn(II) removal capacity. • FMHP exhibited high Mn(II) removal in a wide range of NaCl (0~0.1 M) and pH 2–9. • MnO x layer occurs in-situ and further catalytically oxidizes Mn(II) on FMHP. • Column application of FMH 0.35 P exhibited highly compatible treatment costs. [ABSTRACT FROM AUTHOR]

Novel integration of adsorption followed by catalytic oxidation is expected to be more beneficial for higher Mn(II) removal performance. We prepared self-assembled 3D flower-like Mg(OH) 2 coated on granular-sized polyurethane (namely FMHP) via hydrothermal method at 120 °C under a facile synthesis route. The optimized material, FMHP prepared with 7 g MgO and 20 g polyurethane (FMH 0.35 P), achieved up to 351.2 mg g−1 Mn(II) removal capacity by Langmuir isotherm model. Besides, FMHP exhibited high Mn(II) removal in a wide range of NaCl concentration (0~0.1 M) and pH 2–9. Notably, through consecutive kinetics, BET, XPS, XRD, FESEM, and TEM analyses, it was found that the MnO x layer grows in-situ via ion exchange with Mg(II) on FMHP and further boosts the Mn(II) removal via catalytic oxidation during the Mn(II) removal process. Further, column experiments revealed that the FMH 0.35 P exhibited superior Mn(II) removal capacities up to 135.9 mg g−1 and highly compatible treatment costs ($0.062 m−3) compared to conventional chemical processes. The granular-sized FMH 0.35 P prepared by economic precursors and simple synthesis route revealed a high potential for Mn(II) containing water treatment due to its high removal capacities and easy operation. [Display omitted] • Self-assembled 3D flower-like Mg(OH) 2 coated on granular-sized PU was prepared. • FMH 0.35 P, achieved up to 351.2 mg g−1 Mn(II) removal capacity. • FMHP exhibited high Mn(II) removal in a wide range of NaCl (0~0.1 M) and pH 2–9. • MnO x layer occurs in-situ and further catalytically oxidizes Mn(II) on FMHP. • Column application of FMH 0.35 P exhibited highly compatible treatment costs. [ABSTRACT FROM AUTHOR]

Thermal plasma blasting technology has been widely applied for rock cracking. Though, the application for environmental remediation has yet to be reported. Since the delivery of remediation agents into diesel contaminated clayey zones are exceptionally challenging, herein, this study explores the effect of pilot-scale thermal plasma blasting for soil fracturing and concurrently dispersing the Fenton reagent into the diesel contaminated silty soils. Six times plasma blasting with sole H 2 O 2 at 20 kV had the highest degradation of diesel (>97%) with an equilibrium time of 3 h, and the final diesel concentration was below the South Korean regulated health standard (500 mg kg−1). This study highlights plasma blasting able to deliver H 2 O 2 instantaneously and homogeneously into contaminated zone while promoting Fenton reaction synergism (f syn : 2.04) between H 2 O 2 and ≡Fe surface for effective remediation. Furthermore, the remediation cost (USD 4 metric ton−1) is much lower than most reported in situ technologies. [Display omitted] • First time applying plasma blasting in soil treatment application. • Plasma blasting assist delivery of Fenton reagent into clayey soil. • Solely ≡Fe2+ minerals are sufficient to active Fenton reaction. • Synergistic effect between plasma and Fenton reaction. • Comparatively lower cost (USD30) than conventional treatment. [ABSTRACT FROM AUTHOR]

This study utilized a facile and scalable one-pot wet impregnation method for Hg(II) adsorption to prepare sulfur-anchored palm shell waste activated carbon powder (PSAC-S). The experimental results revealed that the sulfur precursors promote the surface charge on the PSAC and enhance Hg(II) removal via the Na 2 S > Na 2 S 2 O 4 > CH 3 CSNH 2 sequence. PSAC-S prepared using Na 2 S had significant Hg(II) sorption efficiencies, achieving a maximum sorption capacity of 136 mg g−1 from the Freundlich model. Compared to PSAC, PSAC-S had an enhancement in Hg(II) sorption behavior for heterogeneous interactions with sulfur. PSAC-S also demonstrated high Hg(II) sorption capacities over a wide range of solution pH, while ionic strength had an insignificant impact on Hg(II) removal efficiencies. Through various spectroscopic analyses, we identified the mechanisms of Hg(II) removal by PSAC-S as electrostatic interactions, Hg-Cl complexation, and precipitation as HgSO 4. Moreover, PSAC-S unveiled high adsorption affinity and Hg(II) stability in actual groundwater (even in µg L−1 level). These overall results show the potentials of PSAC-S as an alternative, easily scalable material for in-situ Hg(II) remediation. [Display omitted] • A facile and scalable preparation method of PSAC-S is demonstrated. • PSAC-S prepared by Na 2 S has the highest Hg(II) sorption capacity. • PSAC-S exhibits stable Hg(II) adsorption in groundwater after pH adjustment. • The main mechanisms are electrostatic interactions, Hg-Cl complexation, and precipitation. [ABSTRACT FROM AUTHOR]

Atmospheric non-thermal dielectric barrier discharge (DBD) plasma has gained considerable attention due to its cost-efficiency, environmental friendliness, and simplicity. However, certain deficiencies restrict its broad application. Herein, the DBD plasma was used to disrupt three model pharmaceutically active compounds (PhACs), sulfamethoxazole (SMX), ibuprofen (IBP), and norfloxacin (NFX), by varying parameters, such as gas type (Ar, N 2 , O 2 , and air) and flow rate (1–4 L min−1). The air plasma discharge had the highest degradation efficiency, and the air flow rate was optimized at 2 L min−1. However, only 10% of IBP was removed by the sole plasma, whereas NFX and SMX were entirely removed after 30 min. Since the air plasma discharge generates reactive oxygen and nitrogen species in a chained reaction, the remaining NO 2 − and NO 3 − in the aqueous phase were problematic. Therefore, by coupling plasma with electrolysis using Cu/reduced Cu nanowire (R-CuNw) as the anode/cathode, all three PhACs were removed within 30 min, and NO 2 − and NO 3 − were completely reduced to NH 3 with cathodic reduction. Moreover, the electrical energy per order (E EO, 0.04 kWh L−1) and treatment cost (0.003 USD L−1) were much lower than those of the single system. This system demonstrates great potential for water remediation, and the production of NH 3 as a value-added by-product remarkably improves its practicality and is of great importance in agriculture and energy-related industries. [Display omitted] • DBD plasma was insufficient to remove a wide spectrum of PhACs. • Plasma air discharge with 2 L min−1 had the optimal degradation efficiency. • Synergism in E-plasma increased ROS concentration and O 3 solubility. • E-plasma simultaneously removed PhACs and produced NH 3 from NO 3 − • Energy efficiency and treatment cost significantly reduced with E-plasma. [ABSTRACT FROM AUTHOR]

• Mg-Fe-LDH embedded with PAM/PVA for As(III)/As(V) removal was studied for the first time. • PAM 40 /PVA 30 -LDH has higher stability in aqueous phase compared to Mg-Fe-LDH • PAM/PVA delaminated the Mg-Fe-LDH structures and enhances As(III)/As(V) sorption. • Hydrogen bonding, ion exchange of SO 4 2− and complexation are the dominant mechanism for As(III)/As(V) removal. Controlling the particle size and aggregation of nanosheet layers in layered double hydroxides (LDHs) is critical for their application. Herein, we report the preparation of Mg-Fe LDH through a co-precipitation method. The LDH was embedded using polyacrylamide (PAM) and polyvinyl alcohol (PVA; the LDH was designated as PAM/PVA-LDH) for As(III) and As(V) removal. We found that doping with 0.3 mL PVA (2 g L-1) and 0.4 mL (20 g L-1) PAM solution delaminated the nanosheet layers of 1 g of the LDH (PAM 40 /PVA 30 -LDH) and restructured the crystal phase from monoclinic to orthorhombic. This increased the surface area and pore volume. Furthermore, PAM 40 /PVA 30 -LDH exhibited higher affinity for As(III) and As(V) removal with maximum adsorption capacities of 14.1 and 22.8 mg g−1, respectively, compared to LDH alone with adsorption capacities of 7.1 and 7.9 mg g−1, respectively. It was found that the highest adsorption capacities of As(III) and As(V) using PAM 40 /PVA 30 -LDH occurred at pH ∼7 and pH 2.5, respectively. X-ray photoelectron spectroscopy analysis revealed that the removal of As(III) and As(V) on PAM 40 /PVA 30 -LDH was mainly attributable to ion exchange with intercalated SO 4 2-, hydrogen bonding, and complexation mechanisms. These findings illustrate that PAM 40 /PVA 30 -LDH would be an excellent adsorbent for the remediation of arsenic-polluted wastewater. [ABSTRACT FROM AUTHOR]

In this study, palm shell activated carbon powder (PSAC) and magnesium silicate (MgSiO 3) modified PSAC (MPSAC) were thoroughly investigated for fluoride (F−) adsorption. F− adsorption isotherms showed that PSAC and MPSAC over-performed some other reported F− adsorbents with adsorption capacities of 116 mg g−1 and 150 mg g−1, respectively. Interestingly, the MgSiO 3 impregnated layer changed the adsorption behavior of F− from monolayer to heterogeneous multilayer based on the Langmuir and Freundlich isotherm models verified by chi-square test (X2). Thermodynamic parameters indicated that the F− adsorption on PSAC and MPSAC was spontaneous and exothermic. PSAC and MPSAC were characterized using FESEM-EDX, XRD, FTIR and XPS to investigate the F− adsorption mechanism. Based on the regeneration tests using NaOH (0.01 M), PSAC exhibited poor regeneration (<20%) while MPSAC had steady adsorption efficiencies (∼70%) even after 5 regeneration cycles. This is due to highly polarized C–F bond was found on PSAC while Mg–F bond was distinguished on MPSAC, evidently denoting that the F− adsorption is mainly resulted from the exchange of hydroxyl (-OH) group. It was concluded that PSAC would be a potential adsorbent for in-situ F− groundwater remediation due to its capability to retain F− without leaching out in a wide range pH. MPSAC would be an alternative adsorbent for ex-situ F− water remediation because it can easily regenerate with NaOH solution. With the excellent F− adsorption properties, both PSAC and MPSAC offer as promising adsorbents for F− remediation in the aqueous phase. • MgSiO 3 impregnated on PSAC for fluoride removal was studied for the first time. • MPSAC showed higher fluoride adsorption capacities compared to PSAC. • Anions inhibited F− adsorption with the following sequence: Cl− < NO 3 − < SO 4 2-. • PSAC had stable sequestration capacities of fluoride due to strong C–F bond formation. • MPSAC had high regeneration capacities for ex-situ fluoride treatment using NaOH. [ABSTRACT FROM AUTHOR]

• PSAC under UVC 365 irradiation exhibits higher production of O 2 • due to slower e−/h+ recombination than other light sources. • The O 2 • generation from oxygen vacancies associated Si1+ is detected by using EPR spin trapping. • A strong correlation between the content of oxygen vacancies and Si1+ in PSAC and photocatalysis was obtained. • The continuous-flow column of PSAC under UVA 365 irradiation had a > 16-fold longer life than that of the adsorption column. Herein, we discovered and reported oxygen vacancies in silicon oxycarbide containing granular palm shell activated carbon (Si-PSAC) as a photocatalyst under UV irradiation. A strong correlation between the atomic content of Si1+, oxygen vacancies and photocatalytic performance of Si-PSAC was obtained. Based on the electron paramagnetic resonance and photoluminescence analyses, Si-PSAC under UVA 365 irradiation exhibited a higher donor density, better charge transfer and lower electron-hole recombination than that under the other light sources, leading to a higher O 2 · production efficiency. Si-PSAC exhibited effective removal performance for various anionic dyes and endocrine-disrupting chemicals under UVA 365 irradiation. Continuous-flow column tests revealed the life span of Si-PSAC under UVA 365 irradiation was extended by more than 16-fold compared to adsorption column. Since the oxygen vacancies can be created from the naturally present Si in the biomass derived Si-PSAC during the activation, this unexpected discovery of O 2 · production can extend commercially-available Si-PSAC into the full-scale photocatalysis. Image, graphical abstract [ABSTRACT FROM AUTHOR]