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Steam stripping of ammonia from ammonia-rich wastewater (5000–20,000 mg/L) was conducted in a continuous-flow rotating packed bed (RPB) at a pH of 11. This study aimed to elucidate the influence of key operational parameters, including the steam-to-liquid ratio, rotational speed (ω), initial ammonia concentration, steam inlet temperature (TSi), and liquid inlet temperature (TLi), on critical performance metrics such as the ammonia removal efficiency (ARE), the volumetric liquid mass transfer coefficient (KLa), and the concentration of the recovered ammonia solution (CR). The findings revealed that a CR of 22.88 wt.% was achieved under the optimal conditions of a steam-to-liquid ratio of 0.175 kg/kg, an initial concentration of 20,000 mg/L, a TSi of 120 °C, and a TLi of 70 °C. Key experimental factors, including the initial ammonia concentration, TSi, and TLi, significantly impacted the achievement of higher ARE and CR values. The KLa values exhibited a decrease with the increase in the steam-to-liquid ratio, while they increased with ω. However, the KLa remained relatively consistent with ω values within the range of 600 to 1200 rpm. In comparison with prior studies, steam stripping of ammonia exhibits a higher ARE than air stripping with RPB and a higher CR than conventional stripping methods. Moreover, RPB requires a smaller size to achieve equivalent ARE compared to conventional stripping apparatuses. Thus, the steam stripping process with RPB equipment emerges as a suitable method for ammonia recovery from ammonia-rich wastewater. [ABSTRACT FROM AUTHOR]

Emissions and by-products from manufacturing torrefied solid recovered fuel using pulp industry waste containing wood waste with pulp sludge (WPS) were studied. Two batches of WPS1 and WPS2 were tested. The torrefaction of WSP1 and WPS2 were performed at their respectively optimal temperature of 573 and 593 K and time of 20 min, referred as cases WPST1-573-20 and WPST2-593-20, respectively. WPS1 contained higher fixed carbons and volatile matters but lower ash content than WPS2. The results showed that the solid yields of 56 and 61 wt.%, gas yields of 16 and 16 wt.% and liquid yields of 28 and 24 wt.% for WPST1-573-20 and WPST2-593-20, respectively. The maximal concentration of emissions for WPST1-573-20 and WPST2-593-20 are about 1952.5 and 3743.5 ppmv for CO, 26.5 and 156 ppmv for NOx and 31.5 and 392 ppmv for SO2, respectively. The CCO exceeded the emission standard and required further action. The collected non-condensable gases consisted of hydrocarbons ranging from C1-HC to C6-HC, with C4-HC being the predominant component. Here, Cn-HC represents hydrocarbons with a carbon atom count of n. The GC-MS analysis revealed the primary liquid byproducts. The liquid products can be used directly as pyroligneous liquor in agriculture. Furthermore, with refining techniques, these liquid byproducts can be transformed into high-quality chemicals for applications such as fungicides, pesticides, solvents, surfactants, and as precursors or monomers in the synthesis of other chemicals. [ABSTRACT FROM AUTHOR]

This study examined the application of high-gradient magnetic separation (HGMS) for recycling of super-paramagnetic polymer adsorbent (MPA), namely, polyvinyl acetate-iminodiacetic acid. The HGMS can be incorporated with the adsorption and desorption processes (ADPs) with fresh or regenerated desorbed MPAs and exhausted adsorbed MPAs, respectively. This combines the permanent magnet's advantage of low running costs with the easy operation using the solenoid to flush the filter in place. The effects of the inlet concentration of MPA in solution (CLF,i) and the fluid velocity (v0) or volumetric flow rate (QLF) on the performance of the recovery of MPA via HGMS were assessed. The results indicated that the separation efficiency (η or P0), breakthrough time (tB) and exhaustion time (tE) of HGMS reduce as CLF,i, as well as v0, increases. Further, the filter saturated capture capacity (σS) of HGMS also decreases with increasing v0. The effect of v0 on tB proportional to 1/v02 is more significant than that on σS proportional to 1/v0. A kinetic model of HGMS shows good agreements for the experimental and predicted breakthrough results, with determination coefficients of 0.985–0.995. The information obtained in this study is useful for the rational design and proper operation of a HGMS system for the recycling and reuse of MPA in ADPs. [ABSTRACT FROM AUTHOR]

As cobalt (Co) has been the most useful element for activating Oxone to generate SO4•−, this study aims to develop a hierarchical catalyst with nanoscale functionality and macroscale convenience by decorating nanoscale Co-based oxides on macroscale supports. Specifically, a facile protocol is proposed by utilizing Cu mesh itself as a Cu source for fabricating CuCo2O4 on Cu mesh. By changing the dosages of the Co precursor and carbamide, various nanostructures of CuCo2O4 grown on a Cu mesh can be afforded, including nanoscale needles, flowers, and sheets. Even though the Cu mesh itself can be also transformed to a Cu-Oxide mesh, the growth of CuCo2O4 on the Cu mesh significantly improves its physical, chemical, and electrochemical properties, making these CuCo2O4@Cu meshes much more superior catalysts for activating Oxone to degrade the Azo toxicant, Acid Red 27. More interestingly, the flower-like CuCo2O4@Cu mesh exhibits a higher specific surface area and more superior electrochemical performance, enabling the flower-like CuCo2O4@Cu mesh to show the highest catalytic activity for Oxone activation to degrade Acid Red 27. The flower-like CuCo2O4@Cu mesh also exhibits a much lower Ea of Acid Red 27 degradation than the reported catalysts. These results demonstrate that CuCo2O4@Cu meshes are advantageous heterogeneous catalysts for Oxone activation, and especially, the flower-like CuCo2O4@Cu mesh appears as the most effective CuCo2O4@Cu mesh to eliminate the toxic Acid Red 27. [ABSTRACT FROM AUTHOR]

Providing safe drinking water and clean water is becoming a more challenging task all around the world. Although some critical issues and limits remain unsolved, implementing ecologically sustainable nanomaterials (NMs) with unique features, e.g., highly efficient and selective, earth-abundance, renewability, low-cost manufacturing procedures, and stability, has become a priority. Carbon nanoparticles (NPs) offer tremendous promise in the sectors of energy and the environment. However, a series of far more ecologically friendly synthesis techniques based on natural, renewable, and less expensive waste resources must be explored. This will reduce greenhouse gas emissions and harmful material extraction and assist the development of green technologies. The progress achieved in the previous 10 years in the fabrication of novel carbon-based NMs utilizing waste materials as well as natural precursors is reviewed in this article. Research on carbon-based NPs and their production using naturally occurring precursors and waste materials focuses on this review research. Water treatment and purification using carbon NMs, notably for industrial and pharmaceutical wastes, has shown significant potential. Research in this area focuses on enhanced carbonaceous NMs, methods, and novel nano-sorbents for wastewater, drinking water, groundwater treatment, as well as ionic metal removal from aqueous environments. Discussed are the latest developments and challenges in environmentally friendly carbon and graphene quantum dot NMs. [ABSTRACT FROM AUTHOR]

This study investigated the torrefaction of de-oiled Jatropha seed residue after a two-stage sequential process consisting of mechanical screw pressing and solvent extraction using n-hexane (denoted as JMS). The optimal torrefaction temperature (Tr) and torrefaction time (tr) were determined in the ranges of 260–300 °C and 10–60 min, respectively, so to achieve a better heating value and satisfactory energy densification (ED) with acceptable mass loss. Thermogravimetric analysis was employed to elucidate the thermal decomposition behaviors of JMS. By comparison with the torrefaction of Jatropha seed residue after mechanical oil extraction by screw pressing only (namely, JMET), the results indicated that the ED of the torrefaction of JMS yielding the torrefied product JMST (two-stage product) was higher than that of the torrefaction of JME giving the torrefied product JMET (single-stage product). Further, it was found that JMET contained some tar, which was attributed to a thermal reaction in the residual oil in JME during torrefaction. The tar/oil content of JMET was about 1.0–1.8 wt.% in the determined optimal conditions. Thus, the enhanced recovery of the residual oil is advantageous not only because it allows obtaining more oil from Jatropha seed residue with a positive net energy gain but also because it prevents the formation of tar in torrefied biomass products. [ABSTRACT FROM AUTHOR]

Cement is the most widely used construction material in the world. However, its manufacture is high energy consumption and high carbon emission owing to the high temperature calcination process. Geopolymer is an ideal alternative material for cement because it has a similar structure and performance to cement. In addition, it can be synthesized at room temperature and thus has the advantages of energy saving and carbon emission reduction. Sewage sludge (SS) can be used as raw material for geopolymer synthesis. However, the high organic matter content in SS lowers the mechanical strength of geopolymer. Although the organic matter in SS can be removed by incineration at high temperature, this consumes energy and emits carbon dioxide, which diminishes the advantages of geopolymer. In this study, the Fenton method was applied for the removal of organic matter in SS at room temperature. The parameters of the Fenton method, including the dosages of hydrogen peroxide (H2O2) and Fe2+ reagent (FeSO4·7H2O), reaction time, and initial pH value, were investigated. The results indicated that 83.7% of the organic matter in SS could be removed at room temperature by using 5.15 M H2O2 and 5.15 mM FeSO4·7H2O at pH 7, which suggested the possibility of sewage sludge reclamation through geopolymer synthesis as an alternative material for cement toward sustainability. [ABSTRACT FROM AUTHOR]

Combined heat and power production from biogas is now playing an important role in energy and resource utilization as well as pollution control in waste water treatment. This research used biogas from the Bali Sewage Treatment Plant in New Taipei City, Taiwan, as a major source of fuel for the electricity generation. A micro gas turbine electricity generator, Capstone CR-30, which possesses a maximum rated power load (PWL) of 30 kW, was equipped to convert biogas into electricity. The biogas is mainly composed of CH4 (56.1 ± 8.0 vol.%), CO2 (25.5 ± 9.8 vol.%), H2 (0.5 vol.%), and H2S (0.99 ± 0.07 ppmv). During the test operation period of the generator, it was found that the thermal efficiency increases from 19.8% to 23.4% kWhe/kWhth, while the electricity generation efficiency (ηEB) also rises from 0.93 to 1.09 kWhe/m3 biogas as the PWL increases from 10 kW to 30 kW. The results indicated that the generator has a better performance with higher PWL. At PWL = 30 kW, the average adjusted concentrations of CO and NOx (adjusted to 15 vol.% O2) emitted from the generator are 86 ppmv and 17 ppmv, respectively. Both are much lower than the emission standards of stationary sources in Taiwan of 2000 ppmv and 150 ppmv, respectively. Thus, PWL of 30 kW was selected in cooperation with biogas inflow = 0.412 m3/min and air/fuel ratio (i.e., air/biogas ratio) = 76.0 vol./vol. for the long-term regular operation. At the above setting conditions for long-term operation, the generator continuously consumed the biogas and provided stable electricity generation at a rate of 19.64 kWhe/h for a 2-year running period. Moreover, the greenhouse gas can be cut off with a rate of 10.78 kg CO2e/h when using biogas as fuel for electricity generation. Overall, this research proves that the application of a micro gas turbine electricity generator not only has promising performance for using biogas but also gives a significant reduction of greenhouse gas emission, which fits the concepts of the circular economy and environmental protection. [ABSTRACT FROM AUTHOR]

Autoclaving of food wastes (FW) for the resource recovery and reutilization was studied using the pilot plant scale. Experiments were conducted at various temperatures of 408, 428, and 438 K and times of 15 and 60 min. The in-filled steam to the autoclave was supplied by the incineration plant with a gauge pressure of 7 kg/cm2 and a temperature of 443 K or above. The results obtained from the experiments show that the less energy- and time-consuming autoclaving conditions (408 K and 15 min, denoted as Case A408-15) are effective. Comparisons of the properties and characteristics of autoclaved FW (FWA) of Case A408-15 with those of FW are made. The wet bulk volume and wet bulk density of FW A are dramatically reduced to 15.64% and increased to 313.37% relative to those of FW, respectively. This makes the subsequent processing and reuse for FWA more convenient than FW. The autoclaving results in an increase of carbon content and a decrease of nitrogen content, and thus an increase of the C/N ratio of FWA. The contents of sulfur, hemi-cellulose, and cellulose of FWA are also reduced. All these fluctuations are beneficial for making compost or other usages from FWA than FW. The autoclaved liquid product (LA) separated from FWA and liquid condensate (LC) from the released gas possess high COD and TOC. These two liquids can be mixed for use as liquid fertilizers with proper conditioning. Alternatively, further anaerobic digestion of the mixture of FWA, LA, and LC can offer enhanced biogas production for power generation. All these thus match the appeal of sustainable materials management and circular economy. The emitted gas from autoclaving contains no CO and some hydrocarbons. Suitable air pollution control is needed. The results and information obtained are useful for the proper recovery and reuse of abundant food wastes from domestic households and food industries. [ABSTRACT FROM AUTHOR]