Direct Pyrolysis of Reed Black Liquor Droplets in a Fluidized Bed.

Pyrolysis of reed black liquor was tested in the form of both dried powder in a thermogravimeter connected to a mass spectrometer (TG-MS) and fed droplets (RBLD) in an atmospheric fluidized bed at temperatures of 530-780 °C. The effects of temperature were examined to clarify the variations in composition of gaseous products and the microscopic appearance of char. Examination was also performed for the releases of species containing Na, K, and Cl during pyrolysis. The results obtained show that the concentration of combustible components (CH4, H2, and CO) in pyrolysis gas increased with increasing bed temperature to reach 66.1% at 780 °C. There are more Na, K, and Cl releasing into the gaseous product at higher temperatures. The variation in the micromorphology of char from RBLD pyrolysis has been obtained and analyzed.

Strengthened removal of emerging contaminants over S/Fe codoped activated carbon fabricated by a mild one-step thermal transformation scheme.

Thermal transformation of carbonized materials to functional activated carbon (AC) is a simplified, economical and eco-friendly strategy, which has great potential in the practical applications of water purification. Herein, a S/Fe codoped activated carbon (S/Fe@AC) with only 0.90 wt% S and 0.76 wt% Fe was creatively fabricated by one synchronous method of physical activation, carbothermal reduction and sulfidation in the solid phase. The formed iron sulfide shell significantly enhances the antioxidation ability of nanoscale zero-valent iron (NZVI, >180 d) and dramatically improves the hydrophobicity of the composite. Meanwhile, the doped thiophenic S in AC enhances the hydrophobicity and increases the specific surface area to 1194.14 m2 g-1. Incorporating with AC in turn greatly strengthens the dispersibility and stability of sulfurized NZVI particles. Compared to NZVI@AC, AC and NZVI, the removal capacity of S/Fe@AC for the representative hydrophobic contaminant-triclosan (TCS) increases to 519.68 mg g-1 by 66.60%, 78.60% and 981.21%, respectively, outperforming most of the previously reported materials. The strong hydrophobic and π-π interactions, and weak hydrogen bonding and electrostatic repulsion are responsible for the excellent removal performance for TCS. More importantly, the improved chemical property (29.38%) of the composite caused by the doped S/Fe has a greater effect on TCS removal compared with the changed physical structure (14.56%). Furthermore, the stable S/Fe@AC shows strong anti-interference capability and exceptional regenerability. These intriguing discoveries provide new insights into the design of advanced and sustainable adsorbing materials for emerging contaminants.

The synthesis of heterogeneous Fenton-like catalyst using sewage sludge biochar and its application for ciprofloxacin degradation.

The terminal utilization of sewage sludge biochar (SSB) is nonnegligible and significant for sewage sludge (SS) treatment by pyrolysis. In this paper, a novel low-cost recyclable sludge biochar catalyst (SBC) that can be employed as a heterogeneous Fenton-like catalyst was prepared using SSB from SS pyrolysis in a pilot-scale platform for ciprofloxacin (CIP) degradation. The fabricated SBC was analyzed to characterize its surface micrographs, pore structures, and chemical composition. The catalytic effect of SBC on CIP degradation was also explored to determine the feasibility of using SBC to remove aquatic organic contaminants, and its degradation mechanism and pathway were also discussed. SBC can effectively remove CIP by adsorption and enhance the degradation of CIP by its catalytic effect. >80% of the CIP was removed at pH 4.0, and the antimicrobial activity of the resulting products was considerably reduced. The possible degradation mechanism is associated with the synergetic effect of adsorption and oxidative degradation. Oxidizing radical was generated from H2O2 by the activation of Fe2+ and Fe3+, which released from SBC, and HO was the dominant radical in CIP degradation. Piperazine ring cleavage, pyridine cleavage and hydroxylation, F/OH substitution, and defluorination were the dominant degradation pathways. The heavy metal risk assessment showed that SBC exhibits low environmental and ecological risk. This study provides a prospective method for high-value utilization of SSB and a novel and potentially low-cost catalyst for CIP removal from aqueous environments, which is significant for the terminal disposal of SS.

Performance of Pb(II) removal by an activated carbon supported nanoscale zero-valent iron composite at ultralow iron content.

Activated carbon supported nanoscale zero-valent iron composite (NZVI/AC) at ultralow iron content was synthesized and used to remove Pb(II) from aqueous solution. The technical characterization revealed that the loaded amorphous NZVI nanoparticles had a chain-like shape in or close to pores and were found as individual nanospheres with size of approximately 10 nm on the outer surface. The NZVI/AC with the iron content of only 1.57% showed a highly efficient Pb(II) removal performance with 95% of Pb(II) eliminated within 5 min. The adsorption capacity of Pb(II) by NZVI/AC was 59.35 mg g-1 at 298.15 K with a pH of 6.00, which was 8.2 times than that of AC support only. The monitoring of iron release indicated no iron was released at a pH above 4.02. The Pb(II) removal by NZVI/AC was well-represented by a pseudo-second-order kinetics model and showed the behavior of an exothermic process. Essentially, Pb(II) was converted to insoluble forms such as Pb°, PbCO3, Pb(OH)2, PbO or white lead ([2PbCO3·Pb(OH)2]). These reactions were accompanied by the surface oxides aging of NZVI/AC. To summarize, these results represent the first fabrication of NZVI/AC composites with such low iron loading that still present an outstanding Pb(II) removal performance in drinking water purification.