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Fabrication of spherical biochar by a two-step thermal process from waste potato peel
Yang, Xiao,Kwon, Eilhann E.,Dou, Xiaomin,Zhang, Ming,Kim, Ki-Hyun,Tsang, Daniel C.W.,Ok, Yong Sik Elsevier 2018 Science of the Total Environment Vol.626 No.-
<P><B>Abstract</B></P> <P>The aim of this study was to develop a new approach for the preparation of spherical biochar (SBC) by employing a two-step thermal technology to potato peel waste (PPW). Potato starch (PS), as a carbon-rich material with microscale spherical shape, was separated from PPW as a precursor to synthesizing SBC. The synthesis process comprised (1) pre-oxidization (preheating under air) of PS at 220 °C and (2) subsequent pyrolysis of the pretreated sample at 700 °C. Results showed that the produced SBC successfully retained the original PS morphology and that pre-oxidization was the key for its shape maintenance, as it reduced surface tension and enhanced structural stability. The SBC possessed excellent chemical inertness (high aromaticity) and uniform particle size (10–30 μm). Zero-cost waste material with a facile and easy-to-control process allows the method to be readily scalable for industrialization, while offering a new perspective on the full use of PPW.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Potato starch (PS) derived from potato peel waste (PPW) has highly regular spherical shape. </LI> <LI> PS morphology was retained with pre-oxidation process after pyrolysis. </LI> <LI> PS's spherical shape affords great homogeneity to the produced biochar. </LI> <LI> Mechanism of shape maintenance was studied via various spectral characterizations. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Yang, Wen,Ok, Yong Sik,Dou, Xiaomin,Zhang, Yu,Yang, Min,Wei, Dongbin,Xu, Peng Elsevier 2019 Environmental research Vol.175 No.-
<P><B>Abstract</B></P> <P>Breaking down the structural bonds and eliminating the functional groups are more efficient than destroying the whole molecule in antibiotic production wastewater (APW) pretreatment before further biotreatment. Two sulfated titania (TiO<SUB>2</SUB>/SO<SUB>4</SUB>) solid superacids, SSA1 and SSA2 were synthesized, characterized and used for hydrolytic pretreatment of spiramycin in APW. Spiramycin removal followed an order of SSA2>SSA1>TiO<SUB>2</SUB>≈pH = 3>control. The hydrolytic efficiencies increased at elevated temperature from 25 °C to 65 °C. The hydrolytic kinetics followed a first-order model and SSA2 performed the fastest. The performances were positively correlated with both the total acidity determined by <I>n</I>-butylamine titration and the strength of acid sites measured by NH<SUB>3</SUB>-temperature-programmed desorption (TPD). The residual solution for SSA2 presented the least antibacterial potency and anaerobic inhibition among all treatments. The hydrolyzed product was identified as the <I>m/z</I> 699.4321 fragment using UPLC-Q/TOF-MS, which was formed after losing a functional mycarose moiety from the parent molecular. The solid superacids were effective in selectively eliminating 433 mg/L of spiramycin and the antibacterial potencies of the spiramycin production wastewater, which contained very high concentrations of COD (33,000 mg/L). This hydrolytic method avoids using and handling hazardous and corrosive mineral acids on site. It is attractive as a selective catalytic pretreatment method to cleave antibiotics’ functional groups and to reduce its inhibitory effects before sequential biotreatments.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Solid superacids were made by calcining the reaction products of H<SUB>2</SUB>SO<SUB>4</SUB> and titania. </LI> <LI> Functional group breakage was catalyzed by the acid sites of solid superacids. </LI> <LI> The Lewis and Brønsted acidic sites all contributed to the hydrolytic reaction. </LI> <LI> The antibacterial potency and the anaerobic inhibition were effectively decreased. </LI> <LI> Superacids performed well in hydrolytic pretreatment of the production wastewater. </LI> </UL> </P>
The stability and removal of water-dispersed CdSe/CdS core-shell quantum dots from water
Chen, Xu,Ok, Yong Sik,Mohan, Dinesh,Pittman Jr., Charles U.,Dou Jr., Xiaomin Elsevier 2017 CHEMOSPHERE - Vol.185 No.-
<P><B>Abstract</B></P> <P>The increasingly wide use of semiconductor nanocrystals inevitably leads to their release into aquatic environment. The aggregation behaviors of 3-mercaptopropionic acid-capped CdSe/CdS core-shell quantum dots (MPA-QDs) under various water chemistry conditions were examined and their removal using Fe<SUP>3+</SUP> and Al<SUP>3+</SUP> coagulants was evaluated. Cationic species rather than concentrations affected the stability of MPA-QDs. Adding 2 mM Ca<SUP>2+</SUP> led to a much larger ζ-potential decrease and particle size increase than adding 150 mM K<SUP>+</SUP> at each tested solution pH. This indicated that complexation and depletion of surface-bound carboxyl groups by divalent Ca<SUP>2+</SUP> has a more pronounced effect than compression of the electrical double layer by high concentrations of monovalent K<SUP>+</SUP>. The presence of humic acid increased the stability of MPA-QDs, which might increase negative surface charging <I>via</I> overcoating or bind to the surface of MPA-QDs. The nanoparticles exhibited similar aggregation kinetics patterns in tap water and seawater, but varying patterns in the lake water because of the co-existence of 2.3 mM total of Ca<SUP>2+</SUP> and Mg<SUP>2+</SUP>. MPA-QDs (5 mg L<SUP>−1</SUP>) were readily coagulated by 2.4 mM Al<SUP>3+</SUP> or 1.2 mM Fe<SUP>3+</SUP> in tap water. Al<SUP>3+</SUP> and Fe<SUP>3+</SUP> can bind with carboxyl groups of the surface capping ligands, neutralize the negative charges on the surface of MPA-QDs and decrease the electrostatic repulsion forces to induce MPA-QDs aggregation. In addition, MPA-QDs could be bound with and wrapped into the flocs of hydrolysis products of coagulants. The results reported here could help broaden our understanding of the impacts and remediation of water-dispersed core-shell QD nanoparticles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The stability, aggregation and remediation of core/shell QDs were evaluated. </LI> <LI> Ca<SUP>2+</SUP> led to severe aggregation of soluble QDs than K<SUP>+</SUP> at much lower concentrations. </LI> <LI> Depletion of surface bound ligand has a more pronounced effect than compression EDL. </LI> <LI> QDs exhibited different aggregation patterns in tap water, seawater and lake water. </LI> <LI> Both Fe<SUP>3+</SUP> and Al<SUP>3+</SUP> were able to remediate QDs from water but the former was better. </LI> </UL> </P>
Shuhan Sun,Shiling Li,Yibing Hao,Xiao Yang,Xiaomin Dou 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.12
g/C3N4-ZnO composite catalysts were synthesized through surface hybridization of the delocalized conjugated- structure of g/C3N4 with the closely contacted surface of ZnO via a successive and simultaneous calcinationprocedure, and two kinds of photocatalysts, g/C3N4-ZnO1 and g/C3N4-ZnO2, were obtained. Heterojunctions wereformed between the two components, which promote the separation of photogenerated carriers efficiently, and thenenhanced the degradation of 100mg/L of AMX. The degradation rate of g/C3N4-ZnO1 was 1.54, 11.33, and 2.52-foldthat of g/C3N4-ZnO2, g/C3N4, and ZnO, respectively, at a 3.5-h reaction period, with the dosage of 0.3 g/L, and solutionpH at 7.0±0.2. The recycle and reuse ability was excellent and 90.5% of AMX mitigation was achieved in the fifthcycle. For g/C3N4-ZnO1, electrons migrated from the conduction band of g/C3N4 to that of ZnO via the heterojunction. ·OH and h+ were the main active species for AMX degradation, compared to ·O2 dominated for g/C3N4. Twelveintermediate products were identified, and two degradation pathways were inferred for g/C3N4-ZnO1 and g/C3N4-ZnO2, respectively. Finally, transformation products without lactam rings were achieved, which lost most of the antibacterialpotencies, and the ecotoxicity was also dramatically decreased as indicated by the ECOSAR program.