Search Results (6)

This study investigates the potential of cement-less recycled aggregate concrete (C.R.A.C.) as an eco-friendly alternative to traditional ordinary Portland cement (OPC) concrete, using industrial waste (fly ash) and construction and demolition waste (recycled coarse aggregates). This research explores the effects of mixes of varying sodium hydroxide (NH) molarities and percentage substitutions of natural coarse aggregates (N.C.As.) with recycled coarse aggregates (R.C.As.) on the mechanical properties of C.R.A.C. A total of eighteen ambient-cured C.R.A.C. mixes, using Thar Coal fly ash with varying NH molarities (12 M, 14 M, and 16 M), and percentage substitutions of N.C.As. with R.C.As. (0%, 20%, 40%, 60%, 80%, and 100%), were prepared and tested under axial compression and flexure. It was observed that the compressive strength increased by about 76% with an increasing NH molarity, whereas the compressive strength decreased by about 52.9% with an increasing percentage substitution of N.C.As. with R.C.As. The flexural strength increased by about 78.3% with an increasing NH molarity, whereas the flexural strength decreased by about 50.5% with an increasing percentage substitution of N.C.As. with R.C.As. The SEM analysis of the C.R.A.C. mixes highlighted the heterogeneous morphology of fly ash particles (e.g., irregular shape, rough surface texture, and porous regions), which negatively influenced the overall performance of the concrete matrix. The environmental assessment exhibited that the C.R.A.C. mixes exhibited about 45% lower CO₂ emissions than OPC concrete; however, the cost of the C.R.A.C. mixes was about 21% higher than that of OPC concrete mixes. Full article

Municipal solid waste (MSW) is incinerated to reduce the volume and recover energy and materials. The generation of MSW has been increasing over the past few decades due to the increase in population and changing consumption habits. Rising environmental and economic concerns have increased the importance of waste treatment and recovery. Currently, MSW may take three alternate or parallel routes: direct recycling, incineration, or landfill, depending on the country and location. MSW incineration has three products in addition to energy: bottom ash, fly ash, and off-gas. After incineration, bottom ash usually still contains many materials to be recovered, such as glass, ceramics, and metals with a degree of oxidation. This study focuses on aluminium recovery from MSW incineration bottom ash from two different countries. The 2–30 mm fraction of aluminium particles was characterized in terms of its size, shape, and oxide thickness, and its effects on aluminium recovery were investigated. In addition, the ability of mechanical pre-treatment to remove oxides prior to melting was studied. The results were compared with the analytical modeling developed in this study. An increasing particle size and surface area resulted in an increase in aluminium recovery. Mechanical pre-treatment increased the yield for smaller particles to a larger extent than larger particles due to the difference in the oxide/metal ratio. Full article

Carbon-capture technologies are extremely abundant, yet they have not been applied extensively worldwide due to their high cost and technological complexities. This research studies the ability of polymerized fly ash to capture carbon dioxide (CO₂) under low-pressure and low-temperature conditions via physical adsorption. The research also studies the ability to desorb CO₂ due to the high demand for CO₂ in different industries. The adsorption–desorption hysteresis was measured using infrared-sensor detection apparatus. The impact of the CO₂ injection rate for adsorption, helium injection rate for desorption, temperature, and fly ash contact surface area on the adsorption–desorption hysteresis was investigated. The results showed that change in the CO₂ injection rate had little impact on the variation in the adsorption capacity; for all CO₂ rate experiments, the adsorption reached more than 90% of the total available adsorption sites. Increasing the temperature caused the polymerized fly ash to expand, thus increasing the available adsorption sites, thus increasing the overall adsorption volume. At low helium rates, desorption was extremely lengthy which resulted in a delayed hysteresis response. This is not favorable since it has a negative impact on the adsorption–desorption cyclic rate. Based on the results, the polymerized fly ash proved to have a high CO₂ capture capability and thus can be applied for carbon-capture applications. Full article

In this study, magnetic fly ash was prepared with fly ash and nano-magnetic Fe₃O₄, obtained by co-precipitation. Then, a magnetic fly ash/polydimethylsiloxane (MFA@PDMS) sponge was prepared via simple dip-coating PDMS containing ethanol in magnetic fly ash aqueous suspension and solidifying, whereby Fe₃O₄ played a vital role in achieving the uniformity of the FA particle coating on the skeletons of the sponge. The presence of the PDMS matrix made the sponge super-hydrophobic with significant lubricating oil absorption capacity; notably, it took only 10 min for the material to adsorb six times its own weight of n-hexane (oil phase). Moreover, the MFA@PDMS sponge demonstrated outstanding recyclability and stability, since no decline in absorption efficiency was observed after more than eight cycles. Furthermore, the stress–strain curves of 20 compression cycles presented good overlap, i.e., the maximum stress was basically unchanged, and the sponge was restored to its original shape, indicating that it had good mechanical properties, elasticity, and fatigue resistance. Full article

Nanoparticles have gained huge attention in the last decade due to their applications in electronics, medicine, and environmental clean-up. Iron oxide nanoparticles (IONPs) are widely used for the wastewater treatment due to their recyclable nature and easy manipulation by an external magnetic field. Here, in the present research work, iron oxide nanoparticles were synthesized by the sonochemical method by using precursors of ferrous sulfate and ferric chloride at 70 °C for one hour in an ultrasonicator. The synthesized iron oxide nanoparticles were characterized by diffraction light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), electron diffraction spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometer (VSM). The FTIR analysis exhibits characteristic absorption bands of IONPs at 400–800 cm⁻¹, while the Raman spectra showed three characteristic bands at 273, 675, and 1379 cm⁻¹ for the synthesized IONPs. The XRD data revealed three major intensity peaks at two theta, 33°, 35°, and 64° which indicated the presence of maghemite and magnetite phase. The size of the spherical shaped IONPs was varying from 9–70 nm with an average size of 38.9 nm while the size of cuboidal shaped particle size was in microns. The purity of the synthesized IONPs was confirmed by the EDS attached to the FESEM, which clearly show sharp peaks for Fe and O, while the magnetic behavior of the IONPs was confirmed by the VSM measurement and the magnetization was 2.43 emu/g. The batch adsorption study of lead (Pb) and chromium (Cr) from 20% fly ash aqueous solutions was carried out by using 0.6 mg/100 mL IONPs, which exhibited maximum removal efficiency i.e., 97.96% and 82.8% for Pb²⁺ and Cr ions, respectively. The fly ash are being used in making cements, tiles, bricks, bio fertilizers etc., where the presence of fly ash is undesired property which has to be either removed or will be brought up to the value of acceptable level in the fly ash. Therefore, the synthesized IONPs, can be applied in the elimination of heavy metals and other undesired elements from fly ash with a short period of time. Moreover, the IONPs that have been used as a nanoadsorbent can be recovered from the reaction mixture by applying an external magnetic field that can be recycled and reused. Therefore, this study can be effective in all the fly ash-based industries for elimination of the undesired elements, while recyclability and reusable nature of IONPs will make the whole adsorption or elimination process much economical. Full article

Biomasses are organic materials that are derived from any living or recently-living structure. Plenty of biomasses are produced nationwide. Biomasses are mostly combusted and usually discarded or disposed of without treatment as biomass ashes, which include wood and sugarcane bagasse ashes. Thus, recycling or treatment of biomass ashes leads to utilizing the natural materials as an economical and environmental alternative. This study is intended to provide an environmental solution for uncontrolled disposal of biomass ashes by way of recycling the biomass ash and replacing the soils in geotechnical engineering projects. Therefore, in this study, characteristic tests of wood and sugarcane bagasse ashes that are considered the most common biomass ashes are conducted. The test of chemical compositions of biomass ashes is conducted using energy dispersive X-ray spectroscopy (EDS), and Scanning Electron Microscope (SEM), and heavy metal analysis is also conducted. Engineering behaviors including hydraulic conductivity, constrained modulus and shear modulus are examined. Also, coal fly ash Class C is used in this study for comparison with biomass ashes, and Ottawa 20/30 sands containing biomass ashes are examined to identify the soil replacement effect of biomass ashes. The results show that the particle sizes of biomass ashes are halfway between coal fly ash Class C and Ottawa 20/30 sand, and biomass ashes consist of a heterogeneous mixture of different particle sizes and shapes. Also, all heavy metal concentrations were found to be below the US Environmental Protection Agency (EPA) maximum limit. Hydraulic conductivity values of Ottawa 20/30 sand decrease significantly when replacing them with only 1%–2% of biomass ashes. While both the constrained modulus and shear modulus of biomass ashes are lower than Ottawa 20/30 sand, those of mixtures containing up to 10% biomass ashes are little affected by replacing the soils with biomass ashes. Full article