Onsite treatment of wastes in municipal waste incinerator: Co-sintering of fly ash and leachate sludge into value-added ceramic granule.

The leachate sludge (LS) and fly ash (FA) are the foci of hazardous wastes which generated from the municipal solid waste incineration (MSWI). The current work developed a new way to use energy from MSWI process for the on-site sintering of LS and FA at a relatively low temperature. With the assistance of CaF2, granule of LS and MSWI FA were co-sintered. The influence of temperature, the mass of CaF2, and the mass ratio of LS/MSWI FA were investigated. As a result, heavy metals volatilization and leaching in the form of chlorinated salts were controlled. In addition, CaF2 improved the compressive strength of the granule under low-temperature sintering. Moreover, the scale-up co-sintering test was achieved in an MSWI chamber. The results showed that the optimum condition was sintering at 973K for 1 h. The compressive strength of sintered product reached 4.25 MPa, which met the standard of ceramic granule. Moreover, with the addition of CaF2, the volatilization rate of Pb, Zn, and Cd decreased by 6%, 7%, and 6%, respectively. This method can be a promising technique for the utilization of solid wastes.

Preparation and modification of nanocellulose and its application to heavy metal adsorption: A review.

Heavy metals are a notable pollutant in aquatic ecosystems that results in many deadly diseases of the human body after enrichment through the food chain. As an environmentally friendly renewable resource, nanocellulose can be competitive with other materials at removing heavy metal ions due to its large specific surface area, high mechanical strength, biocompatibility and low cost. In this review, the research status of modified nanocellulose for heavy metal adsorbents is primarily reviewed. Two primary forms of nanocellulose are cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs). The preparation process of nanocellulose was derived from natural plants, and the preparation process included noncellulosic constituent removal and extraction of nanocellulose. Focusing on heavy metal adsorption, the modification of nanocellulose was explored in depth, including direct modification methods, surface grafting modification methods based on free radical polymerization and physical activation. The adsorption principles of nanocellulose-based adsorbents when removing heavy metals are analyzed in detail. This review may further facilitate the application of the modified nanocellulose in the field of heavy metal removal.

Application of En Bloc and Urethral Mucosal Flap Sparing Techniques Improve the Functional Outcomes in Holmium Laser Enucleation of Prostate: A Retrospective Case Control Study.

The purpose of the study was to study the feasibility of holmium laser enucleation of prostate (HoLEP) with en bloc and urethral mucosal flap sparing technique in treating benign prostatic hyperplasia (BPH) patients and to evaluate the influence of this modified technique on urinary function. A cohort of 188 BPH patients underwent HoLEP from June 2017 to October 2019. Among them, 92 patients underwent conventional en bloc HoLEP and the other 96 patients underwent HoLEP with en bloc and urethral mucosal flap sparing techniques. The basic characteristics, the volume of the prostate, urodynamic data, and perioperative parameters were recorded for comparison. The outcome parameters include international prostate symptom score (IPSS), maximum urinary flow rate (Qmax), post-voiding residual (PVR), quality of life score (QoL), and incidence of de novo stress urinary incontinence (SUI). The basic characteristics were equivalent in both groups. All HoLEP procedures were smoothly carried out. The perioperative complications were low and did not show a significant difference. The follow-up period was 12 months or longer. IPSS, Qmax, QoL, and PVR were improved postoperation in both groups. There was no statistical difference in the parameters between the two groups. When considering a postoperative SUI, the occurrence of short-term and long-term SUI in the modified HoLEP group was significantly less than those in the conventional HoLEP group (p < 0.05). In summary, HoLEP by using en bloc and urethral mucosal flap sparing technique is a safe and effective treatment for BPH patients, especially in preventing postoperative SUI.

Identification of heavy metal leaching patterns in municipal solid waste incineration fly ash based on an explainable machine learning approach.

The leaching risk of heavy metal (HM) in municipal solid waste incineration fly ash (MSWI-FA) leads to a big challenge for FA landfilling. In this work, the HM leaching patterns were identified via 6 highly available indices of FA, in which 160 stabilized FA samples were collected from 4 incineration plants in eastern China and an explainable machine learning approach based on boosting and game analysis was conducted to assess the leaching potentials of 6 HMs (Cr, Cd, Cu, Ni, Pb and Zn). We found that, there remained high exceeding risks of Cd and Pb in stabilized FA. In addition, the S-Cl (soluble chlorine) content was the most influential factor of the leaching behaviors of Cd, Cu, Pb and Zn, more important than pH in regard to Cu, Pb and Zn. We quantified the influence of S-Cl on the HM leaching of Cd, Cu, Pb and Zn, whereby their leaching concentrations would increase by 223.5%, 215.2%, 216.5% and 222.6%, respectively, for every 0.5 mol/L order increase in S-Cl concentration. Finally, a fast determination criterion for the FA landfill was proposed, that is, FA of which S-Cl was less than 0.412 mol/L was acceptable.

Activation of persulfate via Mn doped Mg/Al layered double hydroxide for effective degradation of organics: Insights from chemical and structural variability of catalyst.

Considerable interest has been focusing on the activation of peroxydisulfate (PDS) by layered double hydroxide (LDH) for degradation of organic pollutants. However, understanding the structure and chemistry of LDH by which the activation of PDS could achieve a high degradation efficiency of organic compounds is an unsolved and fundamental question in advanced oxidation processes (AOPs), and one which, if harnessed, could enable the rational design of LDH with desired material properties. In this work, Mg/Al-LDH was synthesized with variable structures and compositions through doping different proportions of Mn2+. We advanced to understand this question of how LDH by these characteristics can affect the activation of PDS for degradation of organic pollutants. At a relatively low dosage of Mn (˂ 1%) in Mg/Al-LDH, the degradation rate of phenol by LDH activated PDS increased with the increase content of Mn, which was achieved by an increase of catalytic sites in Mg/Al-LDH interlayer. Rather, higher content of Mn (˃ 1%) significantly lowered the degradation performance of phenol as the decrease of interlayer space resulted in reduction of PDS intercalation in LDH and the formation of secondary Mn-related minerals (i.e., Mn3O4) led to meaningless consumption of PDS. Finally, the degradation of phenol by LDH activated PDS followed a non-radical (1O2) mechanism. Our ability to quantify how the chemical and structural variability of LDH influence the activation of PDS for organic degradation could mark an important step toward synthesis strategies for advanced catalysts.

Implementation effect of municipal solid waste mandatory sorting policy in Shanghai.

In Shanghai, the biggest metropolis in China, the source classification of domestic waste began in the 1990s but achieved little success over the past thirty years. Surprisingly, the compulsory classification provision of Shanghai residents' domestic waste since 2019 has been successful. In this work, the overall status, and challenges of municipal solid waste (MSW) management in Shanghai under compulsory waste sorting rules are investigated. We tracked the classification efficiency of municipal solid waste, physicochemical characteristics of separated waste, and the carbon emissions arising from waste disposal system. It was found that almost 83.62 % of household food waste has been effectively separated with high purity of 99.50 %, while the lower heating value (LHV) of residual waste was increased by 96.4 % compared to previous years. With effective waste classification, the net carbon emission of separated processing was reduced to 0.11 ton CE/ton waste. However, this system generated some negative outcomes as well such as the lower recovery value of metal in bottom ash and the higher chloride content in fly ash. Moreover, we have documented and discussed several challenges of sustainable waste management system in Shanghai in the text. In order to overcome those challenges, we recommend to: (i) establish a finer source separation and recycling system; (ii) develop highly-efficient resource recovery technologies of byproducts from waste disposal system; and (iii) propose optimization adjustment strategy for overcapacity in incineration facilities.

Interactions between Cellulose and (1,3;1,4)-ß-glucans and Arabinoxylans in the Regenerating Wall of Suspension Culture Cells of the Ryegrass Lolium multiflorum.

Plant cell walls (PCWs) form the outer barrier of cells that give the plant strength and directly interact with the environment and other cells in the plant. PCWs are composed of several polysaccharides, of which cellulose forms the main fibrillar network. Enmeshed between these fibrils of cellulose are non-cellulosic polysaccharides (NCPs), pectins, and proteins. This study investigates the sequence, timing, patterning, and architecture of cell wall polysaccharide regeneration in suspension culture cells (SCC) of the grass species Lolium multiflorum (Lolium). Confocal, superresolution, and electron microscopies were used in combination with cytochemical labeling to investigate polysaccharide deposition in SCC after protoplasting. Cellulose was the first polysaccharide observed, followed shortly thereafter by (1,3;1,4)-ß-glucan, which is also known as mixed-linkage glucan (MLG), arabinoxylan (AX), and callose. Cellulose formed fibrils with AX and produced a filamentous-like network, whereas MLG formed punctate patches. Using colocalization analysis, cellulose and AX were shown to interact during early stages of wall generation, but this interaction reduced over time as the wall matured. AX and MLG interactions increased slightly over time, but cellulose and MLG were not seen to interact. Callose initially formed patches that were randomly positioned on the protoplast surface. There was no consistency in size or location over time. The architecture observed via superresolution microscopy showed similarities to the biophysical maps produced using atomic force microscopy and can give insight into the role of polysaccharides in PCWs.

A review on fabricating functional materials by heavy metal-containing sludges.

With the development of industry, sustainable use of natural resources has become a worldwide hot topic. Heavy metal-containing sludge (HMS) is a hazardous waste after wastewater treatment. At present, HMS is still treated by landfill or landfill after incineration. Considering the components, HMS usually contains various heavy metals and organic compounds, which is potentially used as a raw resource for catalyst production. This review thus concludes recent reports and developments in this field. First, basic technologies are summarized as component regulation, precursor formation, and structure transformations. Second, prepared materials are applied in various catalytic fields, such as gas purification, photocatalysis, electrocatalysis, and Fenton catalysis. During these processes, key factors are multi-metallic components, metal doping, temperature, and pH. They not only influence the formation of HMS-derived catalyst but also the catalytic activity. Furthermore, catalytic activities of HMS-derived catalysts are compared with those synthesized by pure reagents. An assessment and accounting are also supplied if raw resources are substituted by HMS. Finally, in order to apply HMS in a real application, more works must be devoted to the influence of trace metal doping on catalytic activities and stabilities. Besides, more pilot experiments are urgently necessary.

Mechanochemical activation of titanium slag for effective selective catalytic reduction of nitric oxide.

Ti-bearing blast furnace slag was usually recycled by acid leaching. For the first time, a catalyst was synthesized from the slag by wet ball-milling. During this process, no waste was produced. When the activated slag was used in selective catalytic reduction of nitric oxide (NO), 80.5 ± 1.2% of NO (990 ppm) was removed at 350 °C. The catalyst steadily removed 91.0 ± 1.3% of NO for 900 min at 400 °C. On the contrary, the slag without activation showed almost no catalytic activity at these temperatures. The enhanced activity was mainly attributed to the following characterizations. After wet ball-milling, specific surface area of the slag was increased from 2.595 to 26.497 m2/g; surface acid sites were amplified by 15 times; Fe/Ti ratio on surface was enhanced from 0.20 to 1.10. At the same time, surface Fe2+/Fe3+ was regulated from 0.43 to 0.53. The above enhanced properties were attributed to the mechanochemical activation, which dissolved and re-deposited active species on particle surface as well as reinforced the effect between Fe and Ti species. The main result of this work put forward a green method for the direct utilization of industrial waste without generating by-products.

A density functional theory calculation for revealing environmentally persistent free radicals generated on PbO particulate.

In particulate matter, organic precursors generate environmentally persistent free radicals (EPFRs) on metal oxides and attract worldwide attentions in health risk assessment and environmental protection. For the first time, we determined characteristics and formation processes of EPFRs evolved from different organic precursors on PbO particulate. As a result, phenol resulted in phenoxyl radical at 230 °C by releasing one H atom. One Cl atom was eliminated from monochlorobenzene and 1,2-dichlorobenzene, producing phenyl and chlorobenzene radicals, respectively. The decays of these radicals had an order of chlorobenzene radical (4 d) > phenyl radical (3 d) > phenoxyl radical (2 d). Density functional theory calculations indicated that the long decay of chlorobenzene radical was contributed to the high adsorption energy of 1,2-dichlorobenzene on PbO particulate. Furthermore, chlorobenzene radical produced more reactive oxygen species than the other two radicals in oxidative-stress investigations. Therefore, 1,2-dichlorobenzene creates more persistent EPFR, which will cause more dangerous health impact. The main results of this article provide a new insight into the health risk assessment of organic and oxide-containing particulate matter.

Short-term exposure to ZnO/MCB persistent free radical particles causes mouse lung lesions via inflammatory reactions and apoptosis pathways.

Environmentally persistent free radicals (EPFRs) are easily generated in the combustion processes of municipal solid waste (MSW) and can cause adverse effects on human health. This study focuses on understanding the toxicity of EPFR particles (ZnO/MCB containing EPFRs) to human bronchial epithelial cell lines BEAS-2B and 16HBE, murine macrophages Raw264.7, and the lung of BALB/c mice after a short exposure (7 days). Exposure of BEAS-2B, 16HBE, and Raw264.7 cells to ZnO/MCB particles significantly increased the reactive oxygen species (ROS) production and perturbed levels of intracellular redox conditions (decreased the intracellular GSH level and the activity of cytosolic SOD, and stimulated oxidative stress related proteins such as HO-1 and Nrf2). EPFR particles decreased the mitochondrial membrane potential (MMP) and induced cell apoptosis, including the activation of Caspase-3, Bax, and Bcl-2 apoptotic signalling pathways. A signature inflammatory condition was observed in both cell models and the mouse model for lung lesions. Our data suggest that EPFRs in particles have greater toxicity to lung cells and tissues that are potential health hazards to human lung.

Evaluation of heavy metals stability and phosphate mobility in the remediation of sediment by calcium nitrate.

The injection of oxidants is one of the useful remediation technologies for eliminating hydrogen sulfide (H2 S) and ammonia (NH3 / NH 4 + ) in aquatic sediments. In the current work, the impact of calcium nitrate injection on the release of heavy metals associated with phosphate was evaluated in a column test of sediment with overlying water at a volume ratio of 1:1 for 131 days. Sulfide was significantly oxidized by calcium nitrate, as its amount was reduced substantially by 85% from the 20th to the 30th day, with a decrease in the oxidation-reduction potential to -68 mV and a simultaneous increase in pH to 9.83. Over 50% of the mobile Zn, Pb, and Cu were reprecipitated in the sediment when the phosphate was partially released. It is proposed that the heavy metal immobilization was related to the phosphate content in the pore water due to the precipitation of heavy metals and phosphorus on the surface of Fe hydroxide particles after oxidation. This is supported by chemical fraction analysis of the heavy metals in the sediment, which indicated increased residual fractions of heavy metals. Our results provide an insight into the remediation of sediment by oxidation with a self-stabilization of heavy metals and phosphate. PRACTITIONER POINTS: Effective removal of sulfide after calcium nitrate injection was achieved. Metal immobilization was related to the phosphate content in pore water. Over 50% of mobile Zn, Pb, and Cu might be reprecipitated in sediment. Oxidizable fraction of heavy metal predominantly transformed to its residual fraction.

Resident risk attitude analysis in the decision-making management of waste incineration construction.

Environmental pollutants generated by waste incineration plants, such as heavy metals and dioxin, make surrounding residents very sensitive to the construction of such facilities. This sensitivity and anxiety of residents may induce group events, which further leads to the emergence of social risks. Based on risk perception theory, a total of 320 questionnaires was designed and handed out to residents neighboring to Jiangqiao Waste Incineration Plant in Shanghai, China to detect the factors affecting risk attitude toward such plants. Using ordered logit model, it is found that there are four decisive factors including impact on health, information cognitive, objective characteristics, and the attitude of the neighbors. These factors have different influence on resident risk attitudes, in which the attitude of the neighbors is of most significance, followed by the economic-geography characteristics of residents, the information cognitive has minimal impact.

Efficient activation of intercalated persulfate via a composite of reduced graphene oxide and layered double hydroxide.

Efficient activation of peroxydisulfate (PDS, S2O82-) was achieved in this study by a hybrid of reduced graphene oxide (rGO) and layered double hydroxide (LDH). The peroxydisulfate was intercalated into the interlayers of LDH that was combined with rGO. This sample contributed to 92.4 % of phenol (PhOH) removal at 25 °C with a PDS loading amount of 0.4 mmol/g, which is better than its LDH-PDS counterpart. A high activation of PDS in rGO/LDH-PDS was also observed during the oxidation of 4-bromophenol (4-BrPhOH), 2,4-dibromophenol (2, 4-BrPhOH), 2,6-dibromophenol (2, 6-BrPhOH) and bisphenol A (BPA). As a redox reaction of PDS in LDH, this result determined that the composite of rGO/LDH caused more PDS to be activated than LDH. As the defective rGO sites activated the PDS on the surface or edges of LDH layers, the breaking of the OO bond in PDS generated SO4·- radicals from intercalated peroxydisulfate. This result was supported by the radical scavenger experiment, electron paramagnetic resonance measurements, and the increased number of oxygen functional groups in the reacted rGO. Our work thus provided a novel strategy for PDS activation to use in environmental remediation.

Understanding of the high hydrothermal stability of a catalyst prepared from Mn slag for low-temperature selective catalytic reduction of NO.

Manganese slag is a hazardous waste, which lacks proper treatment. For the first time, an effective catalyst for selective catalytic reduction of nitric oxide was synthesized from manganese slag by a sol-gel method. The obtained catalyst had an excellent low-temperature activity and high hydrothermal stability. It removed 46.3% of nitric oxide (990 ppm) at a temperature as low as 100 °C; its removal increased to 100% at 220 °C, which lasted for more than 2000 min. Moreover, hydrothermal treatment at 400 °C showed little influence on its activity. Even after hydrothermal treatment at 900 °C, the catalyst still removed 39.7% of NO at 220 °C, 22.7% higher than another catalyst synthesized from pure reagents. The hydrothermal stability was attributed to an amorphous layer of MnSixOy. This layer covered the catalyst surface, protected active metal species, pore size and pore volume from steam attacking. Manganese slag thus realized the high-value-added utilization by synthesizing a catalyst with the high hydrothermal stability.

A catalyst with the better catalytic activity for NO reduction showed bigger reduction capacity and limiting current.

The catalytic activity of a new catalyst for NO reduction is usually obtained by a gas-solid phase experiment. For the first time, a relationship has been established between catalytic performance and electrochemistry property. A bimetallic catalyst showed a low-temperature activity and removed 67.27% of NO at 300 °C, 33.39% bigger than a single-metallic catalyst. The bimetallic catalyst removed 9.770 mmol/g of NO after 1440 min, 5.212 mmol/g bigger than the single-metallic one. At the same time, the bimetallic catalyst showed a reduction capacity of 0.441 mmole/g. In comparison, the single-metallic one only had 0.242 mmole/g. Moreover, the limiting current of bimetallic catalyst (4.020 e-4A) was also bigger than that of single-metallic one (3.698 e-4A). Therefore, a catalyst for NO reduction showed better catalytic activity and electron-transfer ability at the same time. In other words, the catalytic activity of a catalyst can be potentially estimated by detecting its electrochemistry properties.

Removal behaviors and mechanisms of orthophosphate and pyrophosphate by calcined dolomite with ferric chloride assistance.

Phosphate is one of the main contaminations in water, so an effective method of decreasing or removing phosphate is needed. The main purpose of this paper is to synthesize CaFe-LDHs and MgFe-LDHs from the mixture of calcined dolomite and ferric chloride to remove orthophosphate and pyrophosphate. The study showed that removal of orthophosphate was attributed to the precipitation by Ca2+ and adsorption by MgFe-LDHs, where the former played a main role. As for pyrophosphate, it was mainly removed by precipitation at the initial pyrophosphate concentration ranging from 3.228 to 17.04 mmol/L. When the initial concentrations became relatively higher, the removal efficiency of pyrophosphate decreased because the complexation effects by Fe3+, Ca2+ and Mg2+ took place.

Improvement on Fluorine Migration from SF6 to SiF4 by an Efficient Mediator of Fe2O3/Cr2O3 Composites.

An economic and facile method was urgently required for the degradation of SF6 to replace the high-energy excitation treatment. Both theoretical calculations and experimental observations were conducted to reveal the synergy of Cr/Fe/Si composites on a new technique of SF6 degradation through reacting silicon dioxide. Density functional theory (DFT) calculations show that strong adsorption of SF6 on Cr2O3, and then the fast F/O exchange between CrF3 and Fe2O3 (energy barrier was 1.45 eV) as well as FeF3 and SiO2 (energy barrier was 1.69 eV) enhanced mediated efficiency from SF6 to SiF4. The fluorine (F) migration between solid interfaces in Cr2O3&Fe2O3@SBA15 was responsible for efficient SF6 removal. The F migration route was composed of SF6 to CrF3, CrF3 to FeF3, and FeF3 to SiF4 with the lowest thermodynamic driving. Enhanced specific accumulative converted amount (SACA) of SF6 on Cr2O3&Fe2O3@SBA15 was achieved and the highest SACA was 13.98 mmol/g within 7 h, significantly higher than that on Fe2O3@SBA15 (5.74 mmol/g) and Cr2O3@SBA15 (2.71 mmol/g). Moreover, X-ray diffractometry and X-ray photoelectron spectroscopy were performed to support DFT calculations, including ion intensities detected using mass spectroscopy and composition analysis of the mediator during the reaction. Therefore, our work put forward a novel approach for economic and efficient SF6 decomposition through reacting with silicon dioxide under the mediation of Cr2O3&Fe2O3. This method was also potentially used in effective degradation of refractory non-metal halides.

Production of an effective catalyst with increased oxygen vacancies from manganese slag for selective catalytic reduction of nitric oxide.

Manganese slag is a solid waste produced by the steel industry and usually lacks a proper recycling. In this paper, the manganese slag was used to synthesize a catalyst via microwave assistant method and applied in selective catalytic reduction of nitric oxide. As a result, the catalyst exhibited an excellent low-temperature activity. It removed 78.31% of nitric oxide at 100 °C, 44.44% higher than that of a slag-derived catalyst synthesized by ammonia impregnation, and 63.18% higher than that of a commercial catalyst. Even after a hydrothermal treatment, the catalyst still showed a removal of 69.26% at 150 °C. After a detailed characterization, the low-temperature activity was attributed to an increased amount of oxygen vacancies, which were generated during the microwave synthesis. The generated oxygen vacancies provided adsorption sites for chemisorbed oxygens, which then promoted the electron transfer for reduction of nitric oxide. The main result of this work will help to develop a low-cost catalyst and obtain a high-value-added utilization of manganese slag at the same time.

Rapid evaluation of leaching potential of heavy metals from municipal solid waste incineration fly ash.

Municipal solid waste incineration fly ash is directly landfilled after solidification in the industry. The rapid evaluation of contaminant leaching is required before the landfill of fly ash. In order to reduce the time to evaluate the effect of solidification, a set of rapid evaluation method was developed through the determination of characteristic index, heavy metal leaching analysis, principal component analysis, and mathematical model construction. It was found that f-CaO, acid neutralizing capacity, pH and soluble calcium were negatively correlated with heavy metal leaching. The soluble chlorine was positively correlated with heavy metal leaching. The effect of each feature indicators on heavy metal leaching was evaluated using principal component analysis and mathematical analysis software R.3.4.4. Furthermore, R.3.4.4 was used to detect the optimal model and the excess probability formula by stepwise linear regression and logistic regression analysis method. By introducing the measured value of feature indicator into the excess probability formula, the rate of excess-standard of heavy metals leaching can be preliminarily determined. Based on the above ideas, a rapid detection and evaluation system could be developed according to the local leaching standards and the components of fly ash selected locally.