RESUMO
This study experimentally investigates the influence of metal chips and glass fibers on the mode I fracture toughness, energy absorption, and tensile strength of polymer concretes (PCs) manufactured by waste aggregates. A substantial portion of the materials employed in manufacturing and enhancing the tested polymer concrete are sourced from waste material. To achieve this, semi-circular bend (SCB) samples were fabricated, both with and without a central crack, to analyze the strength and fracture behavior of the composite specimens. The specimens incorporated varying weight percentages comprising 50 wt% coarse mineral aggregate, 25 wt% fine mineral aggregate, and 25 wt% epoxy resin. Metal chips and glass fibers were introduced at 2, 4, and 8 wt% of the PC material to enhance its mechanical response. Subsequently, the specimens underwent 3-point bending tests to obtain tensile strength, mode I fracture toughness, and energy absorption up to failure. The findings revealed that adding 4% brass chips along with 4% glass fibers significantly enhanced energy absorption (by a factor of 3.8). However, using 4% glass fibers alone improved it even more (by a factor of 10.5). According to the results, glass fibers have a greater impact than brass chips. Introducing 8% glass fibers enhanced the fracture energy by 92%. However, in unfilled samples, aggregate fracture and separation hindered crack propagation, and filled samples presented added barriers, resulting in multiple-site cracking.
RESUMO
An integrated hydrometallurgical process was used for the zinc leaching and purification from a zinc ore containing 9.75 wt% zinc. The zinc minerals in the ore were hemimorphite, willemite, and calcophanite. Main gangue minerals were quartz, goethite, hematite, and calcite. Central composite design (CCD) method was used to design leaching experiments and the optimum conditions were found as follows: 30% of solid fraction, 22.05% sulphuric acid concentration, and the leaching temperature of 45 °C. The PLS containing 35.07 g/L zinc, 3.16 g/L iron, and 4.58 g/L manganese impurities was produced. A special purification process including Fe precipitation and Zn solvent extraction was implemented. The results showed that after precipitation of iron, Zn extraction of 88.5% was obtained with the 2 stages extraction system composed of 30 vol% D2EHPA as extractant. The overall Zn recovery from the ore was 71.44%. Therefore, an appropriate solution containing 16.6 g/L Zn, 0.05 g/L Fe, and 0.11 g/L Mn was prepared for the electro-winning unit without using the roasting and calcination steps (conventional method), which result in environmental pollution.
RESUMO
A green approach was introduced to regenerate Sn-Pb solder from waste printed circuit boards (PCBs). For this purpose, waste Al-based heat sinks were used as cementing agent to precipitate Sn and Pb from pregnant leach solution (PLS) obtained from the dissolution of waste PCBs in HCl. 97 % and 94.9 % of Sn and Pb were recovered, respectively, under optimum conditions at Al powder size of 300⯵m, Al dosage of 1.516â¯g/l and reaction time of 15.41â¯min. Thermodynamic analysis was performed to predict the effect of temperature on the main reactions relevant to the cementation process. The structure of the Sn-Pb cement changed as function of temperature, leading to enhancement of the cementation rate via improving cathodic area. Kinetic modeling indicates that product layer diffusion is the rate limiting step for Sn and Pb cementation. However, the reaction mechanism shifted to chemical reaction control at high temperatures. The results of solder characterization indicated that the melting point of solder was 184.76⯰C. The electrical resistivity and conductivity of the recovered pure alloy were measured to be 34.73 µΩ-cm and 2.88â¯×â¯106 Sm-1, respectively. The characterization revealed that the regenerated product is adequate as an alternative solder alloy.
