This Special Issue (SI), “Recyclable Materials for Ecofriendly Technology”, has been proposed and organized as a means to present recent developments in the field of environmentally friendly designed construction and building materials. For this purpose, dozens of articles were included or considered for inclusion in this SI, covering various aspects of the topic. A comparison of these articles with other modern articles on this topic is carried out, which proves the prospects and relevance of this SI. Furthermore, per the editorial board’s journal suggestion, the second volume of this successful SI is being organized, in which authors from various countries and organizations are invited to publish their new and unpublished research work.

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Recyclable Materials for Ecofriendly Technology

Entropy and exergy analysis of the steam jet condensation in crossflow of subcooled water

In this study, the hydrodynamics of the negatively buoyant supersonic steam jet injected into the water has been investigated based on the effects imparted by its density difference with the water in free and confined configurations. In case of both the upward and downward steam’s free injection, the steam jet-water flow has shown a clear deviation from the non-dimensionalized Boussinesq character. However, in the confined injection, the steam jet creates recirculation regions contributing to enhancing mixing with the water. The generation of recirculation regions owes to the existence of the low-pressure regions at the nozzle exit, baroclinic torque and buoyantly influenced flows, which is associated with the density difference between the steam and water and the shear between the two phases. The buoyancy affects the flow domains in a nonuniform manner. It affects the fluctuating quantities marginally in the jet-developing region, and in the middle section, however, its effect is dominant in the steam jet’s tip region.

Buoyancy effects on the supersonic steam jet injection into cocurrently and countercurrently flowing water

The effect of freeze–thaw (F–T) in the seasonal frozen area would lead to damage to asphalt pavement. After water enters asphalt pavement, the water in voids would expand at a lower temperature, which could change the void content and number, affecting the macro mechanical properties of the asphalt mixture. The rapid development of CT scanning and digital image processing (DIP) provides powerful technical support for the research of asphalt mixture meso volume characteristics. In this paper, the mechanical properties of basalt fiber reinforced asphalt mixture subjected to F–T cycles were tested at different temperatures to clarify the decay law of mechanical properties under F–T cycles. Then, the meso images of the asphalt mixture under various F–T cycles could be obtained by using CT tomography. Based on DIP technology, the meso characteristic parameters of CT images for asphalt mixture were extracted, and the development of asphalt mixture freeze–thaw damage was further analyzed. The test results showed that with the F–T cycle, the macro mechanical properties of the asphalt mixture rapidly declined in the early stage of the F–T cycle and gradually tended to be flat. There would be serious damage inside the asphalt mixture in the late stage of the F–T cycle. The damage to the mechanical properties of the asphalt mixture under the F–T cycle can be attributed to the change in the internal mesostructure of the asphalt mixture. Based on the grey relational analysis theory, the formation of the connected void was the main factor affecting the damage in the early stage of the F–T cycle, while the formation of new voids mainly affected the later development of F-T damage.

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Grey Correlation Analysis between Macro Mechanical Damage and Meso Volume Characteristics of SBS Modified Asphalt Mixture under Freeze-Thaw Cycles

Experimental study on the entrainment of the liquid film in the annular channel of the vortex separator

Turbulence dissipation & its induced entrainment in subsonic swirling steam injected in cocurrent flowing water

To enhance the moisture damage performance of hot mix asphalt (HMA), treating the aggregate surface with a suitable additive was a more convenient approach. In this research, two types of aggregate modifiers were used to study the effect of moisture damage on HMA. Three different aggregate sources were selected based on their abundance of use in HMA. To study the impact of these aggregate modifiers on moisture susceptibility of HMA, the indirect tensile strength test and indirect tensile modulus test were used as the performance tests. Moisture conditioning of specimens was carried out to simulate the effect of moisture on HMA. The prepared samples’ tensile strength ratio (TSR) and stiffness modulus (Sm) results indicated a decrease in the strength of the HMA after moisture conditioning. After treating the aggregate surface with additives, an improvement was seen in dry and wet strength and stiffness. Moreover, an increasing trend was observed for both additives. The correlation between TSR and strength loss reveals a strong correlation (R2 = 0.7219). Also, the two additives indicate increased wettability of asphalt binder over aggregate, thus improving the adhesion between aggregate and asphalt binder.

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Evaluation of Moisture Damage Potential in Hot Mix Asphalt Using Polymeric Aggregate Treatment


 Global indicators have warned of freshwater scarcity in Asia. However, the utilization of freshwater resources has skyrocketed for commercial and industrial purposes without any strategy for recycling and reuse. The power plant's wastewater/reject mainly consisted of cooling tower blowdown water and reverse osmosis (RO) plant reject water. Due to the high turbid nature of reject water, pretreatment was carried out to achieve SDI15 <3 by employing multimedia filters (MMF), activated carbon filters (ACF) and ultrafiltration (UF). Operational parameters of RO membranes were optimized (11.5 bar, 29 °C) to achieve maximum water recovery along with higher rejection rates of critical scale forming species such as 81% total dissolved solids (TDS), 73% calcium hardness and 72% silica (Si). After accounting for backwash water and other concentrate rejections, the membrane treatment plant has achieved an appreciable recovery rate of more than 44%. The RO membrane-treated water was then incorporated in the cooling tower and a 16% reduction in freshwater makeup was achieved. Reduction of microbial growth rate as well as corrosion and scaling in the cooling tower was observed due to the reuse of treated water. This is to confirm here that brackish water RO membranes can act as a strong contender for reject water reclamation and effective utilization.

https://iwaponline.com/jwcc/article-pdf/doi/10.2166/wcc.2023.071/1240385/jwc2023071.pdf

Application of UF and RO for power plant's wastewater treatment and recycling for environmental sustainability

CO2 reforming of methane (CRM) is becoming a hot research area because of its capability to utilize greenhouse gases to reduce global warming. However, the CRM has not yet been commercialized due to several challenges including the weak prospect of catalyst. The impact of strontium on the performance of a monometallic Ni-MgO/ZrO2 catalyst was examined in this study. Mixed oxide MgO-ZrO2 support was prepared by coprecipitation method followed by wetness impregnation of Ni and Sr metals. N2−physisorption analysis and X-Ray Diffraction (XRD) were employed to evaluate the fresh catalysts in order to investigate their physicochemical properties. The Ni-Sr/MgO-ZrO2 catalyst provided the optimum catalytic performance for the CRM reaction carried out in a tabular fixed bed reactor at 800 °C with a CH4CO2 ratio of 1:1. Due to the formation of amorphous carbon nanosheets that covered the active sites of the monometallic Ni/MgO-ZrO2 catalyst, its activity decreased, whereas the Ni-Sr/MgO-ZrO2 catalyst's activity was maintained due to filamentous carbon formation. 

Muhammad Umar Mushtaq

Papers

Turbulence dissipation & its induced entrainment in subsonic swirling steam injected in cocurrent flowing water

Evaluation of Moisture Damage Potential in Hot Mix Asphalt Using Polymeric Aggregate Treatment

Application of UF and RO for power plant's wastewater treatment and recycling for environmental sustainability

Performance of Ni-Sr/MgO-ZrO2 catalyst for CO2 reforming of methane: Effect of Sr addition