Physical Characterization and Pre-assessment of Recycled High-Density Polyethylene as 3D Printing Material

3D printing has received lots of attention due to its limitless potential and advantages in comparison to traditional manufacturing processes. This study focuses on the most popular type of home 3D printers, namely fused filament fabrication (FFF) printers, which use plastic filaments as the feedstock. The rather high material cost and large amount of plastic waste generated by FFF 3D printers have driven the need for plastic filaments produced from recycled plastic waste. This study evaluates, in terms of physical characterization, the feasibility of using recycled high-density polyethylene (HDPE), one of the most commonly used plastics, as the feedstock for 3D printers, in comparison with the common acrylonitrile butadiene styrene plastic pellets. In-house extrusion using recycled HDPE pellets and flakes is possible. The diameter consistency and extrusion rate results, along with other physical characterization results, including differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, and water absorption, suggest that making filaments from recycled HDPE pellets is a viable option, as the obtained filament has favorable water rejection and comparable extrusion rate and thermal stability. Existing methods for overcoming the warping and adhesion problems in 3D printing with HDPE were also reviewed. In order to increase the market competitiveness of waste-derived filaments, optimization of the extrusion process, studies on the mechanical and aging properties, and development of a standard characterization methodology and database are crucial.     

Analysis of interprovincial trade embodied carbon emissions in Beijing-Tianjin-Hebei and surrounding provinces: based on constructed MRIO Model

The interprovincial trade embodied carbon emissions plays an important role in the national emission reduction target among China’s provinces. Furthermore, it will affect the smooth start-up of the national carbon trade market as well as the implementation of targets in 2030 for dealing with the climate change. Based on constructed MRIO model, this paper analyzes the embodied carbon emission trade flows among Beijing, Tianjin, Hebei and surrounding regions such as Shanxi, Shaanxi, and Inner Mongolia. The results indicate that six provinces have formed different patterns of carbon trade balance, where Beijing, Tianjin, and Hebei provinces are in a deficit position, while the other three provinces are in a surplus position. Beijing, Tianjin, and Hebei have transferred part of the carbon emissions to the other three provinces, which shows greater heterogeneity among various provinces and provincial different sectors. On basis of the conclusions, this paper puts forward some suggestions on provincial decomposition, responsibility distribution, and provincial collaborative reduction for national emission reduction targets.     

Relationship of urinary arsenic metabolites to intake estimates in residents of the Red River Delta, Vietnam

This study investigated the status of arsenic (As) exposure from groundwater and rice, and its methylation capacity in residents from the Red River Delta, Vietnam. Arsenic levels in groundwater ranged from <1.8 to 486 μg/L. Remarkably, 86% of groundwater samples exceeded WHO drinking water guideline of 10 μg/L. Also, estimated inorganic As intake from groundwater and rice were over Provisional Tolerable Weekly Intake (15 μg/week/kg body wt.) by FAO/WHO for 92% of the residents examined. Inorganic As and its metabolite (monomethylarsonic acid and dimethylarsinic acid) concentrations in human urine were positively correlated with estimated inorganic As intake. These results suggest that residents in these areas are exposed to As through consumption of groundwater and rice, and potential health risk of As is of great concern for these people. Urinary concentration ratios of dimethylarsinic acid to monomethylarsonic acid in children were higher than those in adults, especially among men, indicating greater As methylation capacity in children.     

好氧与厌氧氨氧化复合颗粒污泥完全自营养脱氮影响因素

采用间歇实验,考察了初始NH⁺₄-N浓度、DO浓度和pH对颗粒污泥完全自营养脱氮的特性的影响。研究表明,在完全自营养脱氮系统中,当DO为0.6～0.8 mg/L,pH控制在7.5～7.8时,好氧氨氧化和厌氧氨氧化速率在一定范围内随NH⁺₄-N浓度（30～150 mg/L）的增加而增加,较高的氨氮浓度能提高自营养脱氮反应速率。较高的DO有利于提高亚硝酸盐氧化速率,但会导致亚硝酸盐的积累;DO浓度过低时,好氧氨氧化过程受到抑制。NH⁺₄浓度为36 mg/L,DO控制在0.6～0.8 mg/L的条件下,当pH值为7.8时,完全自营养脱氮的效果最佳,总氮去除速率达最大值为23.976 mg/(g MLSS·d)。     

Residential water demand and water waste in Taiwan

Environmental Economics and Policy Studies - Residential water demand has long been an important topic of empirical research. How to estimate water waste, however, has rarely been touched. Using...     

Recycling of the hyperaccumulator Brassica juncea L.: synthesis of carbon nanotube-Cu/ZnO nanocomposites

The methods of synthesizing carbon nanotube (CNTs)-Cu/ZnO nanocomposites using a Cu hyperaccumulator (Brassica juncea L.) constitute a new insight into the recycling of hyperaccumulators and provide a new route for the further development of green nanostructure syntheses. In this paper, CNTs-Cu/ZnO nanocomposites have been synthesized using B. juncea plants as the sources of C, Cu, and Zn. The synthesized CNTs-Cu/ZnO nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectra (EDS). The synthesized CNTs were characterized further by selected area diffraction (SAD) patterns and Raman spectroscopy. The results demonstrated that the structure of individual CNTs was middle-hollow, with an outer diameter of about 80 nm. The synthesized CNTs were not at all crystalline and there were a few defects in the walls. The outer diameter of CNTs-Cu/ZnO nanocomposites was 110 nm. The diameters of Cu/ZnO nanoparticles were 29.5/32.7 nm, respectively. Cu/ZnO nanoparticles that had grown onto the CNT surface were nonuniform and agglomerated. The Cu/ZnO nanoparticles were pure.     

Disinfection byproduct formation from algal organic matters after ozonation or ozone combined with activated carbon treatment with subsequent chlorination

Algal organic matter (AOM), including extracellular organic matter (EOM) and intracellular organic matter (IOM) from algal blooms, is widely accepted as essential precursors of disinfection byproducts (DBPs). This study evaluated the effect of ozonation or ozone combined with activated carbon (O₃-AC) treatment on characteristic alternation and DBP formation with subsequent chlorination of Chlorella sp.. The effects of pH and bromide concentration on DBP formation by ozonation or O₃-AC treatment were also investigated. Results showed that the potential formation of DBPs might be attributed to ozonation, but these DBP precursors could be further removed by activated carbon (AC) treatment. Moreover, the formation of target DBPs was controlled at acidic pH by alleviating the reactions between chlorine and AOM. Besides, the bromide substitution factor (BSF) value of trihalomethanes (THMs) from EOM and IOM remained constant after AC treatment. However, THM precursors could be significantly decreased by AC treatment. The above results indicated that O₃-AC was a feasible treatment method for algal-impacted water.     

Enrichments of Trace Metals in Particulate Matter From the Southern East China Sea, North of Taiwan

This study investigates the distributions and enrichments of trace metals in suspended and sinking particulate matter from southern East China Sea (ECS) north of Taiwan during the period April 1992 to April 1993. According to these results, concentration of suspended particulate matter in the inner shelf of southern China Sea, the upwellinginfluenced shelf break, and in Kuroshio water are 1.30 (surface)-4.2 (bottom) mg1^-1, ca. 0.4 mg1^-1 and 0.1-0.2 mg1^-1, respectively, reflecting various influences of terrestrial inputs. A benthic nepheloid layer (BNL), apparently owing to resuspension of local and/or remote bottom sediments, formed over the shelf region. Temporal variations in trace metal contents and enrichments in suspended matter from the shelf region reflect the variation of metal inputs from Chinese rivers, particularly from the Changjiang runoff. the enriched metals are more likely to be derived from anthropogenic input, rather than from biological accumulation. in addition, a decrease in metal contents and an increase in salinity confirm the transport of suspended particulate metals from the East China Sea shelf to the open ocean. the feature of metal plume in the intermediate layer (550-800m) of Kuroshio water also verifies this occurrence. Moreover, the sinking particles collected from a sediment trap on the upper slope are relatively enriched in lithogenic matter and trace metals, suggesting the deposit of anthropogenic metals in the slope area.     

基于异养-硫自养反硝化耦合技术的陶粒-硫磺混合生物填料对城市污水处理厂尾水的深度脱氮

针对城市污水处理厂脱氮能力的不足,设计了2种不同体积比的陶粒-硫磺混合生物填料反应器(陶粒与硫磺的体积比分别为2∶1和5∶1),并用其对城市污水处理厂尾水进行了深度处理。结果表明,陶粒与硫磺体积比为2∶1的混合生物填料反应器(R2,高硫耦合组)在C/N为4,HRT为4 h的条件下处理模拟废水时脱氮效率最高,TN平均去除率和平均出水质量浓度分别为(92.62±1.36)%和(2.39±0.22) mg∙L^-1。相比于R1(异养对照组),R2在保证脱氮效率的同时,碳源投加量更少;此外,R2在最佳条件下促进了体系内反硝化微生物群落Thauera(陶厄氏菌属)和Thiobacillus(硫杆菌属)的生长,二者的相对丰度之和为39.13%。     

废铅蓄电池回收的节能降碳案例分析

为了解我国废铅蓄电池回收过程的节能降碳现状,以典型废铅蓄电池回收工艺为研究对象,分析了废铅蓄电池回收过程的产品综合能耗和碳排放情况。结果表明,案例企业的单位产品综合能耗 (当量能耗) 为98.35 kgce·t⁻¹;天然气消耗是最大的能耗来源;铅膏熔炼工序是废铅蓄电池回收过程中产品综合能耗和碳排放量最大的工序;焦粉作为还原剂进入熔炼工序的排放是最主要的碳排放源。在燃料燃烧、能源作为原材料、净购入电力和热力方面,能耗和碳排放量核算是线性相关的,在上述方面寻求节能措施可使废铅蓄电池回收企业实现同时降碳。此外,碳酸盐引起的过程排放和耗能工质也会影响企业的节能降碳效果,建议在后续的核算指南中进行统一规定。本研究结果可为废铅蓄电池回收过程的节能降碳提供参考。