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Enhanced sludge dewaterability using a bifunctional hybrid coagulant

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Chemosphere 2023年 344卷 140323页

作者： Shen, Shaohang Xia, Wei Luo, Zhang Pan, Yu Hu, Pan Zhang, Longguan Shi, Hongtao Yang, Hu State Key Laboratory of Pollution Control and Resource Reuse School of the Environment Nanjing University Nanjing210023 China China Railway Engineering Services Co. Ltd. Chengdu610083 China

The combination of coagulation and addition of skeleton builder is a popular pretreatment method to improve the dewaterability of sludge. In this study, a novel bifunctional inorganic/organic hybrid coagulant (CS–Si@ATP) was designed and obtained by chemically coupling a cationic starch (CS) with a popular clay, that is, attapulgite (ATP), via a silane coupling agent (APTES) for one-step conditioning of sludge. CS-Si@ATP can evidently enhance the sludge dewatering performance compared with CS, ATP, and their simple combination due to the distinct dual functions of this hybrid coagulant. The tentacle-like cationic CS in CS-Si@ATP shows efficient charge neutralization effect to aggregate and precipitate the suspended solids for further formation of compact sludge cakes. Meanwhile, the internal ATP with a stable and rigid structure acts as the skeleton builder to notably improve the filterability and permeability of the sludge cakes. The synergistic effects of CS and ATP in CS-Si@ATP, i.e., the charge neutralization of CS and the skeleton construction of ATP, cause the evidently enhanced sludge dewaterability, with a filter cake moisture content approximately 78.30% after the mechanical dewatering at 0.05 MPa. In comparison with the traditional two-step combination process by separated addition of CS and ATP, the one-step addition of CS-Si@ATP can reduce the required ATP dose nearly an order of magnitude. Thus, CS-Si@ATP has the notable advantages of simple operation, efficient utilization of ATP and evident reduction of disposal cost. This study provides an environmentally friendly and cost-effective coagulant to further improve the dewaterability of sludge. © 2023 Elsevier Ltd

关键词： Starch

Insights into in Situ Surface Reconstruction in Cobalt Perovskite Oxides for Enhanced Catalytic Activity

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SSRN 2024年

作者： Jin, Yanyu Cheng, Hongjun Wang, Qibao Liu, Xiaoqing Mo, Shengpeng Zhou, Bin Peng, Yue Wang, Yu Si, Wenzhe Li, Junhua School of Environmental Science and Engineering Yancheng Institute of Technology Yancheng224051 China State Key Joint Laboratory of Environment Simulation and Pollution Control School of Environment Tsinghua University Beijing100084 China School of Environment and Safety Engineering North University of China Taiyuan030051 China School of Chemical & Environmental Engineering China University of Mining and Technology Beijing100084 China

An depth understanding of the fundamental interactions between surface termination and catalytic activity is crucial to prompt the properties of functional perovskite materials. The elastic energy due to size mismatch and electrostatic attraction of the charged Sr dopant by positively charged oxygen vacancies induced inert A-site surface enrichment rearrangement for perovskites . Lower temperatures could reduce A-site enrichment, but it is difficult to form perovskite crystals. La0.8Sr0.2CoO3-δ (LSCO) as a model perovskite oxide was modified with additive urea to reduce the crystallization temperature, and suppress Sr segregation. The LSCO catalysts with 600°C annealing temperature (LSCO-600) exhibited a 19.4-fold reaction reactivity of toluene oxidation than that with 800°C annealing temperature (LSCO-800). Combined surface-sensitive and depth-resolved techniques for surface and sub-surface analysis, surface Sr enrichment was effectively suppressed due to decreased oxygen vacancy concentration and smaller electrostatic driving force. DFT calculations and in-situ DRIFTS spectra well reveal that tuning the surface composition/termination affects the intrinsic reactivity. The catalyst surface with lower Sr enrichment could easily adsorb toluene, cleave, and decompose benzene rings, thus contributing to toluene degradation to CO2. This work demonstrates a green and efficient way to control surface composition and termination at the atomic scale for higher catalytic activity. © 2024, The Authors. All rights reserved.

关键词： Perovskite

Recycling Phosphorus from Waste in China: Recycling Methods and Their environmental and Resource Consequences

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SSRN 2022年

作者： Liu, Xuewei Zhang, You Yuan, Zengwei State Key Laboratory of Pollution Control and Resource Reuse School of the Environment Nanjing University Nanjing210023 China

Recycling phosphorus (P) from waste is an effective way to alleviate resource and environmental pollution due to excessive phosphate consumption. In order to better understand the feedback of phosphorus cycle to waste recycling methods, a P waste feedback model was built to predict P waste generation, recycling, loss patterns and phosphate consumption in China under several scenarios. Three recycling methods, waste as fertilizer, waste as feed and waste as industrial material, were analyzed for each scenario. The results show that dietary change causes sharp increase in P loss and phosphate consumption, but the integrated measures can offset the increase. ‘Waste as fertilizer’ has greater reduction in phosphate consumption, ‘waste as feed’ method effectively mitigates P loss, and 'waste as material' method is less effective. Integrated measure with ‘waste as fertilizer’ method minimizes the pressure of phosphate reserve depletion, but the economically recoverable reserve would still be depleted around 2053. © 2022, The Authors. All rights reserved.

关键词： Water pollution

Revisiting the Role of H2o2 in Periodate Electro-Activation System: The Non-Dependence in Pollutant Removal

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SSRN 2024年

作者： Zhou, Zhengwei Ye, Guojie Zong, Yang Zhao, Zhenyu Hou, Chengsi Chen, Zuofeng Wu, Deli State Key Laboratory of Pollution Control and Resources Reuse College of Environmental Science & Engineering Key Laboratory of Urban Water Supply Water Saving and Water Environment Governance in the Yangtze River Delta of Ministry of Water Resources Shanghai Institute of Pollution Control and Ecological Security Tongji University Shanghai200092 China Shanghai Key Laboratory of Chemical Assessment and Sustainability School of Chemical Science and Engineering Tongji University Shanghai200092 China

The existence of hydrogen peroxide (H2O2) within the electro-activation of periodate (PI) system is conventionally considered as conducive to the removal of pollutants. However, this study discovered an unusual phenomenon: the pollutants removal did not depend on H2O2. The removal efficiency of pollutants and the yield of hydroxyl radical (·OH) are enhanced after quenching H2O2. Therefore, this study aims to revisit and delve deeper into the role of H2O2, particularly in the generation of active species. Mixed metal oxide and graphite felt are selected as the anode and cathode for the activation of PI in Bisphenol A (BPA) degradation. There exist two distinct pathways for PI activation, including direct cathodic electroreduction and indirect in-situ generated H2O2 catalysis. The BPA removal efficiency increased after adding catalase, with all efficiencies exceeding 80% within 40 minutes. Meanwhile, multiple probing techniques clearly identify the variety of active species and generation pathway such as Electron paramagnetic resonance (EPR), LC-QTOF-MS, and quenching experiment. Electrogenerated H2O2 serves as a precursor for the generation of superoxide radical anions (O2·-) and singlet oxygen (1O2), yet it diminishes the efficiency of direct cathode activation due to the consumption of PI. Furthermore, the system demonstrated excellent stability, applicability, and cleanliness, effectively removing contaminations without the accumulation of iodine byproducts. The degradation intermediates products of BPA are monitored and the toxicities are evaluated. The study provides novel insights into the regulation of active species for contaminant elimination and electrode design, holding significant implications for specialized sewage treatment. © 2024, The Authors. All rights reserved.

关键词： Hydrogen peroxide

Effects of a Redox-Active Diketone On the Photochemical Transformation of Roxarsone: Mechanisms and environmental Implications

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SSRN 2022年

作者： Wei, Shuangshuang Zhou, Chang Zhang, Guoyang Zheng, Hongcen Chen, Zhihao Zhang, Shujuan State Key Laboratory of Pollution Control and Resource Reuse School of the Environment Nanjing University Nanjing210023 China

Organoarsenics pose a severe threat to the environment and human health. In aquatic environment, dissolved organic matter (DOM)-mediated photochemical transformation is one of the main processes in the fate of variant pollutants, including organoarsenics. Dicarbonyl is a typical redox-active moiety in DOM. However, the knowledge on the photoconversion of organoarsenics by DOM, especially the contributions of dicarbonyl moieties is still limited. Here, we systematically investigated the photochemical transformation of three organoarsenics with the simplest β-diketone, acetylacetone (AcAc), as a model dicarbonyl moiety of DOM. The results demonstrate that AcAc was a potent photo-activator and oxygen-depleting agent, which could significantly enhance the photochemical transformation of roxarsone (ROX). At a 1:1 molar ratio of AcAc to ROX, the photochemical transformation rate of ROX was increased by 7 folds. In O2-rich environment, singlet oxygen, peroxide radicals, and ·OH were the main reactive species that led to the breakage of the C-As bond in ROX and the oxidation of the released arsono group to arsenate, whereas the triplet-excited state of AcAc (3AcAc*) and carbon-centered radicals from the photolysis of AcAc dominated in the reductive transformation of ROX. In anoxic environment, 3-amino-4-hydroxyphenylarsonic acid was one of the main reductive transformation intermediates of ROX, whose photolysis rate was about 35 times that of ROX. The knowledge obtained here is of great significance to better understand the fate of organoarsenics in natural environment. © 2022, The Authors. All rights reserved.

关键词： Dissolved oxygen

Deciphering the Roles of Diketone-Derived Defects on Graphite Carbon Nitride in Boosted Photocatalytic Production of H2o2

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SSRN 2022年

作者： Yang, Jianghua Ji, Zewen Zhang, Shujuan State Key Laboratory of Pollution Control and Resource Reuse School of the Environment Nanjing University Nanjing210023 China

The fabrication and identification of defects for enhanced photocatalytic production of hydrogen peroxide (H2O2) by carbon nitride (CN) remain challenging, because of the multiple pathways involved in production of H2O2. Here, a simple route was employed to generate defects in CN by employing acetylacetone (AcAc) as a modifying precursor. In this way, modified CN with dual defects (-OH and C doping) was successfully fabricated by tuning the ratio of AcAc to urea (AxCN). The photocatalytic yield of H2O2 was up to 3629 μmol·g-1·h-1. The ultrahigh H2O2 production was attributable to the synergistic roles of -OH group and C defect. The C defects enhanced the anchoring of dioxygen, while -OH group facilitated the diffusion of charge carriers. As a result, the selectivity of H2O2 production was increased from 60% (CN) to 85% (A0.05CN). This work provides new insight into green production of H2O2. © 2022, The Authors. All rights reserved.

关键词： Carbon nitride

Highly Efficient and Selective Extraction of Phosphorous from Wastewater as Vivianite in a Strategically Operated Four-Chamber Flow Electrode Capacitive Deionization

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SSRN 2022年

作者： Liang, Peng He, Yunfei Zhang, Xiaori Zuo, Kuichang Yang, Fan Gao, Tie State Key Joint Laboratory of Environmental Simulation and Pollution Control School of Environment Tsinghua University Beijing100084 China The Key Laboratory of Water and Sediment Sciences Ministry of Education College of Environment Sciences and Engineering Peking University Beijing100871 China

Phosphorus (P) is not only one of the main contaminants in wastewater but also an essential nutrient for all living organisms. In this study, we demonstrate a highly efficient and selective process for extraction of P from wastewater in the form of solid vivianite using a strategically operated four-chamber flow electrode capacitive deionization (FC-FCDI). The separated diluate and concentrate chambers in FC-FCDI enables continuous production of dephosphorylated water and P-rich brine, realizing P removal rate (0.22 μmol/(cm2 ·min)) and enrichment efficiency (concentration factor of 17.2) much higher than previous studies. The spontaneously enriched competing ions in the concentrate mitigate their further migration due to concentration countering effect, realizing to date the highest selectivity for P over SO42- (4.4) in CDI systems. Most importantly, the precipitated vivianite has high P content (12.4%) and much smaller volume compared with the P-recovered solution in previous studies. The recovery of P in the solid state prevents the production of brine wastes, requires no water input for concentrate replenishment, and is conducive to transport, storage, and direct usage for various purposes. This work suggests a novel method for highly selective and efficient extraction of P from wastewater using tailor-designed and strategically-operated FC-FCDIs. © 2022, The Authors. All rights reserved.

关键词： Extraction

Enhanced synergistic removal of Cu(II) and Cr(VI) with multifunctional biomass hydrogel from strong-acid media

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Chemosphere 2023年 345卷 140490页

作者： Wang, Liting Jiang, Yanni Lu, Lingxiao Zhang, Weiguo Li, Tanshang Liu, Zicheng Liu, Fuqiang Li, Aimin State Key Laboratory of Pollution Control and Resource Reuse School of the Environment Nanjing University Nanjing210023 China Nanjing University & Yancheng Academy of Environmental Protection Technology and Engineering Yancheng224000 China

Simultaneous recovery of heavy metal ions (HMIs) such as Cu(II) and Cr(VI) from strong-acid media was a great challenge due to the inhibition of protons. Herein, a novel biomass hydrogel (CMC/PEI-PD) containing various groups (bis-picolylamine, amino, and hydroxyl groups) was newly prepared by a facile two-step process. The static experiments relating pH, kinetics and isothermal co-adsorption confirmed the synergistic effect towards Cu(II) and Cr(VI) consistently. Specifically, the adsorption capacities of Cu(II) and Cr(VI) at pH 2.0 increased by 23.73% and 40.18% in comparison with the single systems. Moreover, coexistence of inorganic anions and cations could further increase the adsorption of Cu(II) and Cr(VI) by 59.90% and 43.39%, respectively. At the same time, the adsorption and desorption ratios for both HMIs remained stable. The superior performance came from the two dominant mechanisms of co-removal. On the one hand, Cu(II) chelated by bis-picolylamine group attracted Cr(VI) in the form of cation bridge, thus promoting Cr(VI) adsorption. On the other hand, the protonated amine group attracted Cr(VI) by electrostatic interaction and weakened the inter-cationic repulsion by electrostatic shielding, thus promoting Cu(II) adsorption. In addition, the dynamic column experiment towards simulated acidic electroplating wastewater involving Cu(II)–Cr(VI)–Ni(II) certified the high efficiency and feasibility of the co-removal. Therefore, CMC/PEI-PD owned great potential in the separation of typical HMIs even directly from strong-acid media. © 2023 Elsevier Ltd

关键词： Biomass

Removal of algae and algogenic odor compounds via combined pre-chlorination and powdered activated carbon adsorption for source water pretreatment

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Separation and Purification Technology 2023年 304卷

作者： Zheng, Zheng-Xiong Lin, Yi-Li Fang, Ruo-Fan Zhou, Xiao-Yang Liu, Zhi Dong, Zheng-Yu Zhang, Tian-Yang Xu, Bin State Key Laboratory of Pollution Control and Resource Reuse Key Laboratory of Yangtze Water Environment Ministry of Education College of Environmental Science and Engineering Tongji University Shanghai200092 China Shanghai Institute of Pollution Control and Ecological Security Shanghai200092 China Department of Safety Health and Environmental Engineering National Kaohsiung University of Science and Technology Kaohsiung824 Taiwan

This study investigated the combination sequence and time interval of chlorination and powdered activated carbon (PAC) adsorption for the control of algae inactivation, algogenic odor removal, and disinfection by-product (DBP) formation. Results indicated that pre-chlorination/post-PAC exhibited the highest algae removal efficiency in all sequential combinations of PAC adsorption and chlorination, while it had displayed slight effect on the removal of DBPs. The evaluated sequential combinations all had significant effect on the removal of odor. Nevertheless, prolonged time interval between chlorination and PAC adsorption exhibited enhanced control of algae and odor compounds in all experiments;with increasing time interval from 0 to 15 min in pre-chlorination/post-PAC process, the removal efficiency of Chl-a, algal cell viability, GSM, and 2-MIB increased by 46%, 15%, 15% and 23%, respectively. In the combined processes, the odor removal efficiency was positively correlated with PAC dosage but negatively correlated with chlorine dosage. Furthermore, PAC addition could effectively reduce the total DBP yields, especially the N-DBPs. This study can provide a better understanding of improving in-situ operation of the pre-chlorination and PAC dosing systems for source water pretreatment. © 2022 Elsevier B.V.

关键词： Algae