Polyprodrug nanomedicine for chemiexcitation-triggered self-augmented cancer chemotherapy and gas therapy.

Carbon monoxide (CO) has emerged as a potential antitumor agent by inducing the dysfunction of mitochondria and the apoptosis of cancer cells. However, it remains challenging to deliver appropriate amount of CO into tumor to ensure efficient tumor growth suppression with minimum side effects. Herein we developed a CO prodrug-loaded nanomedicine based on the self-assembly of camptothecin (CPT) polyprodrug amphiphiles. The polyprodrug nanoparticles readily dissociate upon exposure to endogenous H2O2 in the tumor, resulting in rapid release of CPT and generation of high-energy intermediate dioxetanedione. The latter can transfer the energy to neighboring CO prodrugs to activate CO production by chemiexcitation, while CPT promotes the generation of H2O2 in tumors, which in turn facilitates cascade CPT and CO release. As a result, the polyprodrug nanoparticles display remarkable tumor suppression in both subcutaneous and orthotopic breast tumor-bearing mice owing to the self-augmented CPT release and CO generation. In addition, no obvious systemic toxicity was observed in mice treated with the metal-free CO prodrug-loaded nanomedicine, suggesting the good biocompatibility of the polyprodrug nanoparticles. Our work provides new insights into the design and construction of polyprodrug nanomedicines for synergistic chemo/gas therapy.

Water washing and acid washing of gasification fly ash from municipal solid waste: Heavy metal behavior and characterization of residues.

Gasification fly ash (GFA) is a hazardous solid residue generated in the slagging-gasification of municipal solid waste (MSW). GFA contains higher amounts of heavy metals such as Pb and Zn than incineration fly ash (IFA), which increases the difficulty of heavy metal immobilization but simultaneously makes it a potential feedstock for metal recovery. Water washing and acid washing are conventional and economic methods to treat wastes with high heavy metal and chloride contents. However, the research on the effects of such methods in treating GFA is still blank. Hence, in this study, water washing and acid washing of GFA were investigated in detail. Heavy metal behaviors at different time points during the washing processes were studied in a wide pH range and comprehensive characterizations of washed GFAs were also conducted. The results show that different re-precipitates could be identified in washed GFAs depending on different pH conditions. After water washing for 24 h, more than 60% of Zn in GFA would dissolve and re-precipitate into calcium zincate. It is also revealed that the precipitation effect could in turn influence the pH during the washing process. After acid washing with a low-concentration acid, heavy metal leachabilities were found reduced due to the pH and precipitation effect. High-concentration acid washing could effectively extract Zn and Cd with extraction ratios exceeding 90%. Applying 1.2 M-HCl washing, a short washing period of 15 min could realize a Pb extraction ratio of 81.2%, much higher than 53.2% when extending the washing period to 24 h.

Carbonation of municipal solid waste gasification fly ash: Effects of pre-washing and treatment period on carbon capture and heavy metal immobilization.

Carbon capture has become an important technology to mitigate ever-increasing CO2 emissions worldwide, and alkali waste is a potential source of CO2 capture material. Slagging-gasification is a novel technology for treating municipal solid waste (MSW), and the gasification fly ash (GFA) is the only solid residue that is not reused at present due to its high heavy metal content. GFA contains high amounts of Ca(OH)2 and Ca(OH)Cl, making it protentional for CO2 capture. In this study, GFA and washed gasification fly ash (WGFA) were treated with CO2 for different treatment periods. Weight changes of samples were recorded to evaluate the efficiency of CO2 capture. To assess the properties of treated GFA, pH value, leached heavy metal concentration, mineral composition, and microscopic morphology were studied. The results revealed that GFA and WGFA could adsorb 18.8% and 23.7% CO2 of their weights, respectively. Carbonation could immobilize heavy metals including Pb, Zn, and Cu when a proper treatment period was applied. An excessive treatment period decreased the efficiency of heavy metal immobilization. Pre-washing is recommended as a pre-treatment method for GFA carbonation, which increased the efficiency to adsorb CO2, improved the pH of carbonated GFA, and enhanced the effect to immobilize heavy metals.

Characterization and comparison of gasification and incineration fly ashes generated from municipal solid waste in Singapore.

Slagging-gasification has received increasing attention as a municipal solid waste treatment technology. Compared with incineration, slagging-gasification can produce valuable syngas and generates by-products that can be easier reusable in different applications in some cases. Among these by-products, the gasification fly ash (GFA) is the only hazardous solid residue to be landfilled. To explore its potential recycling methods and maximize its recycling efficiency, the detailed physicochemical properties of GFA are crucial. This study conducted a comprehensive characterization of six GFA samples and the results were compared with one incineration fly ash (IFA) sample and available data of IFA collected in Singapore in literature. X-ray fluorescence (XRF), and microwave acid digestion (MAD) followed by inductively coupled plasma optical emission spectroscopy (ICP-OES) and inductively coupled plasma mass spectroscopy (ICP-MS) were carried out to determine the physicochemical composition of ashes. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were applied to identify their mineralogical composition. The hazard of the material was assessed through one-stage batch leaching tests. The results showed that the GFAs and IFA were both mainly composed of calcium compounds and chloride salts. However, GFA contained higher amounts of heavy metals especially lead (Pb) and zinc (Zn) than IFA. Zn contents in tested GFA samples were in a range of 1.4-3.0%, indicating the potential to recover Zn. The Ca(OH)2 content in GFA samples was up to 24.1%, which could be recovered as a low-grade lime. Based on the characteristics of GFA, a reusing method combining civil engineering utilization and resource recovery was suggested.

Treating Pb-contaminated clay slurry by three curing agents.

Each year, extensive dredged clay slurries containing heavy metals need to be treated before being reused; in such contaminated slurries, lead (Pb) is frequently identified. Quicklime (CaO)-activated ground granulated blast-furnace slag (GGBS), magnesium (MgO)-activated GGBS, and ordinary Portland cement (OPC) are usually used to remediate the lead (Pb)-contaminated soil; nevertheless, using these curing agents (or binders), particularly CaO-GGBS and MgO-GGBS, to treat Pb-contaminated slurry with high water content is rarely reported. Moreover, inconsistent results were obtained from previous studies in terms of the mechanical and leaching performance of Pb-contaminated soils with the three binders. Based on the above-mentioned reasons, this study used CaO-GGBS, MgO-GGBS, and OPC to treat the Pb-contaminated clay slurry, and compared the effectiveness of the three binders in improving the mechanical and leaching properties of the slurry. Laboratory tests were performed to examine the leaching, strength, mineralogical, and micro-structural performance of treated clay slurries. The results showed that GGBS-based binders were more effective than OPC in improving the strength and Pb leachability of contaminated slurries. When suitable ratios between activators (CaO and MgO) and GGBS were used, a similar or even higher UCS was produced by CaO-GGBS than MgO-GGBS. Similar leachate pH and Pb leachability could be achieved between CaO-GGBS- and MgO-GGBS-treated contaminated clay slurries. Therefore, it is not rigorous to state that MgO-GGBS is better in improving the strength and leachability of Pb-contaminated soils than CaO-GGBS only by comparing the two GGBS-binders based on the same activator/GGBS ratio, as reported in some previous studies. The leachability of Pb was affected by the pH, but the addition of GGBS facilitated the decrease of Pb leachability in slurries. The XRD result showed the formation of CSH and Pb(OH)2, which facilitated the reduction of Pb leachability.

Carbonation treatment of gasification fly ash from municipal solid waste using sodium carbonate and sodium bicarbonate solutions.

In recent years, slagging-gasification technology has received increasing attention in treating municipal solid waste (MSW). Compared with conventional incineration, the higher temperature in the slagging-gasification process optimizes its residue composition, and gasification fly ash (GFA) is the only unreused solid residue. Although GFA is a potential civil engineering material, its high content of heavy metals, chlorides, and sulfates hinders its practical use. Moreover, although carbonation has proven to immobilize heavy metals in incineration fly ash, the conventional gas carbonation method cannot remove chlorides and sulfates. In this study, sodium bicarbonate (NaHCO3) treatment was studied to treat GFA for the first time, and sodium carbonate (Na2CO3) was used for comparison. Different concentrations of NaHCO3 and Na2CO3 solutions were used to treat the GFA, and comprehensive tests were conducted on the treated samples. The results indicated that NaHCO3 treatment was effective in immobilizing Pb, Zn, Cu, and Ni in GFA, while Na2CO3 treatment could not effectively immobilize Pb and Zn. Both NaHCO3 and Na2CO3 promoted the removal of chlorides and sulfates in GFA. The wastewater from the NaHCO3 treatment contained fewer heavy metals compared with those from water washing or Na2CO3 treatment, benefitting its treatment or reuse.

The role of freshwater sludge and its carbonaceous derivatives in the removal of lead, phosphorus and antibiotic enrofloxacin: Sorption characteristics and performance.

Freshwater sludge (FS) produced from drinking water treatment plants is generally filter pressed and disposed in the landfill. However, FS could be potentially reused. In this study, FS were processed into biochar and hydrochar via pyrolysis and hydrothermal carbonization, respectively. The sorption characteristics/mechanisms of FS and its derivatives (biochar-B300, B500 and B700 and hydrochar-H140, H160, H180 and H200) for the removal of three typical pollutants (i.e., lead (Pb), phosphorus (P) and enrofloxacin (ENR)) found in swine wastewater were investigated using batch adsorption tests and microstructural analyses. It was found that Pb sorption was relatively enhanced due to the increased electrostatic attraction and surface precipitation of Pb(OH)2 while the anionic phosphate adsorption relatively decreased as a result of enhanced electrostatic repulsion at higher solution pHs. Comparatively, ENR adsorption was less affected by solution pH probably due to dominance of physical adsorption evidenced by the good fitting of the BET isotherm model (R2 = 0.95). The maximum sorption capacities of Pb were in the order of B700≈B500 (71 mg/g)>B300 ~ FS(37 mg/g)>H140 ~ H160 (13 mg/g)>H180 ~ H200 (6 mg/g). The adsorption capacities for P were relatively lower: FS (47 mg/g)>B300 (38 mg/g)>H140 (27 mg/g)>B700 (37 mg/g)≈B500 (24 mg/g)≈H160 (23 mg/g)>H180 (16 mg/g)>H200 (14 mg/g). This study provides an understanding of the sorption characteristics and mechanisms of FS and its carbonaceous products for common cationic, anionic and organic pollutants and elucidates new insights into the reuse of FS for pollutant removal to achieve the waste-to-resource concept and enhance water quality, soil health and food safety.

Biochar and hydrochar derived from freshwater sludge: Characterization and possible applications.

Freshwater sludge (FS) is generated in large quantities during the production of drinking water every day. It is largely underutilized, and has long been filter pressed to sludge cake and then disposed of in landfills. The search for more economical and sustainable disposal or reuse options is urgently needed. Biochar and hydrochar are increasingly popular wastes derived materials with huge potential for soil improvement, environmental remediation, and mitigation of climate change, but there is a lack of research on the production of FS derived biochar and hydrochar. In this study, biochar was produced by pyrolysis at 300, 500 or 700 °C for 1 h, and hydrochar was produced by hydrothermal carbonization (HTC) at 140, 160, 180 or 200 °C for 4 h. Proximate analyses show that the biochar has a higher carbon stability and is possibly suitable for carbon sequestration, while the hydrochar contains more labile carbon structures. The ultimate analysis indicates that the surface hydrophobicity is in the order of: biochar > hydrochar > FS. The phytotoxicity tests indicate their positive effects on germination of wheat seeds. This study provides a new treatment to reuse numerous FS and put forward the possible applications of its carbonaceous products, which is expected to facilitate a circular economy and realize the zero-waste target.

Carbonating MgO for treatment of manganese- and cadmium-contaminated soils.

Ordinary Portland cement (OPC) and lime are commonly used to treat soils contaminated by heavy metals, such as cadmium (Cd) and manganese (Mn). However, the production of these two binders is not sustainable, consuming high energy and emitting high carbon dioxide (CO2). In this contest, this study proposed a novel and sustainable method of carbonating magnesia (MgO) for treatment of Cd- and Mn-contaminated soils, which can sequester CO2 and immobilize Cd and Mn in the soils. To validate the method, a range of experiments were performed. First, MgO and CO2 were used to treat contaminated soils. Then, the properties of the treated soils were evaluated by unconfined compressive strength test, one stage batch leaching test, X-ray diffraction test, and thermogravimetric analysis. It was found that the carbonation process of MgO-treated soils was decelerated by Mn, but not significantly decelerated by Cd. After carbonation, multiple magnesium carbonates were formed in both contaminated soils, and CdCO3 was formed in the Cd-contaminated soil, while MnCO3 was not confidently determined in the Mn-contaminated soil. Both Cd and Mn negatively affected the strength of carbonated MgO-treated soils; nevertheless, if the concentration of Cd or Mn was not more than 8000 mg/kg, 5% MgO-treated soils after carbonation could meet the strength requirement of higher than 1000 kPa. The treatment decreased the Cd leachability to be below the limit for non-hazardous wastes. The leached concentration of Mn was decreased to be lower than the limit of drinking water.

Polydnavirus of Campoletis chlorideae: characterization and temporal effect on host Helicoverpa armigera cellular immune response.

Polydnavirus was isolated from oviduct calyx in the parasitoid wasp Campoletis chlorideae (Hymenoptera: Ichneumonidae), and termed CcIV. The virus particles consist of fusiform nucleocapsids surrounded by two unit membrane envelopes. The DNAs purified from these viruses were found diversified in molecular weight and existed in nonequimolar concentrations. At least 20 different-sized bands were present after electrophoresis, and they ranged from approximately 3 to 26 kb. Persistence and gene expression of CcIV were examined in parasitized and virus-injected Helicoverpa armigera larvae. Viral DNA could be detected in the hemocyte of H. armigera at 30 min post-parasitization (p.p.), and persisted for 6 days. While no viral DNA increase was found, CcIV transcripts were first detected in host hemocytes at day 1 p.p. and continued for 5 days. Similar transcripts were observed in hemocytes from larvae that had been injected with calyx fluid or CcIV 24 h earlier. CcIV viral DNAs hybridized only with certain first-strand cDNAs from hemocytes, suggesting that only part of the CcIV genome was expressed in H. armigera. The pattern of CcIV gene expression was consistent with that of the inhibition of encapsulation for Sephadex G-10 and parasitoid eggs by host larvae. The recovery of host immune response at day 4 p.p. indicated that CcIV exhibited a partial and temporal effect on the host immune system and the developing parasitoid appeared to avoid encapsulation via different mechanisms.