Insights into the electron transfer mechanisms of permanganate activation by carbon nanotube membrane for enhanced micropollutants degradation

● A CNT filter enabled effective KMnO₄ activation via facilitated electron transfer. ● Ultra-fast degradation of micropollutants were achieved in KMnO₄/CNT system. ● CNT mediated electron transfer process from electron-rich molecules to KMnO₄. ● Electron transfer dominated organic degradation. Numerous reagents have been proposed as electron sacrificers to induce the decomposition of permanganate (KMnO₄) by producing highly reactive Mn species for micropollutants degradation. However, this strategy can lead to low KMnO₄ utilization efficiency due to limitations associated with poor mass transport and high energy consumption. In the present study, we rationally designed a catalytic carbon nanotube (CNT) membrane for KMnO₄ activation toward enhanced degradation of micropollutants. The proposed flow-through system outperformed conventional batch reactor owing to the improved mass transfer via convection. Under optimal conditionals, a > 70% removal (equivalent to an oxidation flux of 2.43 mmol/(h·m²)) of 80 μmol/L sulfamethoxazole (SMX) solution can be achieved at single-pass mode. The experimental analysis and DFT studies verified that CNT could mediate direct electron transfer from organic molecules to KMnO₄, resulting in a high utilization efficiency of KMnO₄. Furthermore, the KMnO₄/CNT system had outstanding reusability and CNT could maintain a long-lasting reactivity, which served as a green strategy for the remediation of micropollutants in a sustainable manner. This study provides new insights into the electron transfer mechanisms and unveils the advantages of effective KMnO₄ utilization in the KMnO₄/CNT system for environmental remediation.     

Composting of waste algae: A review

Although composting has been successfully used at pilot scale to manage waste algae removed from eutrophied water environments and the compost product applied as a fertiliser, clear guidelines are not available for full scale algae composting. The review reports on the application of composting to stabilize waste algae, which to date has mainly been macro-algae, and identifies the peculiarities of algae as a composting feedstock, these being: relatively low carbon to nitrogen (C/N) ratio, which can result in nitrogen loss as NH₃ and even N₂O; high moisture content and low porosity, which together make aeration challenging; potentially high salinity, which can have adverse consequence for composting; and potentially have high metals and toxin content, which can affect application of the product as a fertiliser. To overcome the challenges that these peculiarities impose co-compost materials can be employed.     

Synthesis of branched,nano channeled,ultrafine and nano carbon tubes from PET wastes using the arc discharge method

Upcycling polymer wastes into useful, and valuable carbon based materials, is a challenging process. We report a novel catalyst-free and solvent-free technique for the formation of nano channeled ultrafine carbon tubes (NCUFCTs) and multiwalled carbon nanotubes (MWCNTs) from polyethylene terephthalate (PET) wastes, using rotating cathode arc discharge technique. The soot obtain from the anode contains ultrafine and nano-sized solid carbon spheres (SCS) with a mean diameter of 221 nm and 100 nm, respectively, formed at the lower temperature region of the anode where the temperature is approximately 1700 °C. The carbon spheres are converted into long “Y” type branched and non-branched NCUFCTs and MWCNTs at higher temperature regions where the temperature is approximately 2600 °C, with mean diameters of 364 nm and 95 nm, respectively. Soot deposited on the cathode is composed of MWCNTs with a mean diameter of 20 nm and other nanoparticles. The tubular structures present in the anode are longer, bent and often coiled with lesser graphitization compared to the nanotubes in the soot on the cathode.     

How certain are we about the certainty-equivalent long term social discount rate?

Theoretical arguments for using a term structure of social discount rates (SDR) that declines with the time horizon have influenced government guidelines in the US and Europe. The certainty equivalent discount rate that often underpins this guidance embodies uncertainty in the primitives of the SDR, such as growth. For distant time horizons the probability distributions of these primitives are ambiguous and the certainty equivalent itself is uncertain. Yet, if a limited set of characteristics of the unknown probability distributions can be agreed upon, ‘sharp’ upper and lower bounds can be defined for the certainty-equivalent SDR. Unfortunately, even with considerable agreement on these features, these bounds are widely spread for horizons beyond 75 years. So while estimates of the present value of intergenerational impacts, including the social cost of carbon, can be bounded in the presence of this ambiguity, they typically remain so imprecise as to provide little practical guidance.     

低碳高氮污水处理应用技术研究

针对碳氮比小于7的污水,其碳源不能满足硝化与反硝化的要求这一问题,通过改变SBR工艺的运行方式、调解工艺参数等技术手段,使其能够达标处理此类工业废水,并通过某淀粉厂的工程实例进行了验证:采用改良的SBR工艺可以对低碳高氮污水进行有效的处理。     

Effect of oxide-based fluxes on mechanical and metallurgical properties of Dissimilar Activating Flux Assisted-Tungsten Inert Gas Welds

Present investigation is to study the “Effect of Activating Fluxes on Mechanical and Metallurgical Properties of Dissimilar Activated Flux-Tungsten Inert Gas Welds”. Effect of current, welding speed, joint gap and electrode diameter on weld bead dimensions on 6 mm thick dissimilar weld between carbon steel to stainless steel, was studied under Activated Flux-Tungsten Inert Gas Welding process. During this investigation three different types of oxide powders were used-TiO₂, ZnO and MnO₂. After welding samples were subject to mechanical testing, in addition to characterization via micro hardness and microstructures of Normal Tungsten Inert Gas Welds and Activated Flux-Tungsten Inert Gas Welds. Activating fluxes TiO₂ and ZnO are effective fluxes for Activated Flux-Tungsten Inert Gas Welding of dissimilar weld between CS to SS. Highest depth/width (D/W) ratio reported under TiO₂ and ZnO fluxes compare to Normal-Tungsten Inert Gas Welds. Lowest angular distortion was observed under TiO₂ flux compare to Normal-Tungsten Inert Gas Welds. Mechanical properties, Joint Efficiency of Activated Flux-Tungsten Inert Gas Welds are higher than normal-Normal Tungsten Inert Gas Welds. Tensile Test specimens of both the processes failed from the parent metal (carbon steel side). Carbon migration from CS to SS, had occurred which led to failure of weld joints from CS side.     

Pd-MnO2 nanoparticles/TiO2 nanotube arrays (NTAs) photo-electrodes photo-catalytic properties and their ability of degrading Rhodamine B under visible light

Pd-MnO_2/TiO_2 nanotube arrays(NTAs) photo-electrodes were successfully fabricated via anodization and electro deposition subsequently; the obtained Pd-MnO_2/TiO_2 NTAs photo electrodes were analyzed by scanning electron microscopy(SEM), X-ray diffraction(XRD) and characterized accordingly. Moreover, the light harvesting and absorption properties were investigated via ultraviolet–visible diffuse reflectance spectrum(DRS); photo degradation efficiency was investigated via analyzing the photo catalytic degradation of Rhodamine B under visible illumination(xenon light). The performed analyses illustrated that Pd-MnO_2 codoped particles were successfully deposited onto the surface of the TiO_2 nanotube arrays;DRS results showed significant improvement in visible light absorption which was between400 and 700 nm. Finally, the photo catalytic degradation efficiency results of the designated organic pollutant(Rhodamine B) illustrated a superior photocatalytic(PC) efficiency of approximately 95% compared to the bare TiO_2 NTAs, which only exhibited a photo catalytic degradation efficiency of approximately 61%, thus it indicated the significant enhancement of the light absorption properties of fabricated photo electrodes and their yield of UOH radicals.     

Effects of sludge retention time, carbon and initial biomass concentrations on selection process: From activated sludge to polyhydroxyalkanoate accumulating cultures

Four sequence batch reactors (SBRs) fed by fermented sugar cane wastewater were continuously operated under the aerobic dynamic feeding (ADF) mode with different configurations of sludge retention time (SRT), carbon and initial biomass concentrations to enrich polyhydroxyalkanoate (PHA) accumulating mixed microbial cultures (MMCs) from municipal activated sludge. The stability of SBRs was investigated besides the enrichment performance. The microbial community structures of the enriched MMCs were analyzed using terminal restriction fragment length polymorphism (T-RFLP). The optimum operating conditions for the enrichment process were: SRT of 5 days, carbon concentration of 2.52 g COD/L and initial biomass concentration of 3.65 g/L. The best enrichment performance in terms of both operating stability and PHA storage ability of enriched cultures (with the maximum PHA content and PHA storage yield (Y_PHA/S) of 61.26% and 0.68 mg COD/mg COD, respectively) was achieved under this condition. Effects of the SRT, carbon concentration and initial biomass concentration on the PHA accumulating MMCs selection process were discussed respectively. A new model including the segmentation of the enrichment process and the effects of SRT on each phase was proposed.     

低碳经济背景下我国产业结构升级对策研究

为了实现我国经济的平稳发展,改变以"高消耗、高增长、高污染"的传统经济增长方式,解决资源的过度消耗和温室气体的过量排放等问题,文章从我国产业及内部结构、产业的碳排放量和产业节能率三个方面进行了分析,提出了在低碳经济背景下实现我国产业结构升级的对策。