Study of Semi-Dry High Target Solidification/Stabilization of Harmful Impurities in Phosphogypsum by Modification

Phosphogypsum (PG) treatment is one of the research hotspots in the field of environmental protection. Many researchers both at home and abroad have devoted themselves to studies on harmless resource treatment of PG, but the treatment technology is unable to meet the demand of PG consumption due to the huge production and storage demands. In order to solve the problem of PG pollution, this study explored the different solidified effects of various modification formulations on the hazardous components in PG, using industrial solid waste calcium carbide slag (CCS) as an alkaline regulator; Portland cement (PC), polyaluminum chloride (PAC) and CaCl2 as the main raw materials of the solidification and stabilization formula and the water content in PG as the reaction medium. The results showed that CCS (0.5%), PC (0.4%) and PAC (0.3%) had a more significant solidified effect on phosphorus (P) and fluoride (F). PAC was added in two steps and reacted under normal temperature and pressure, and its leaching toxicity meets the requirements of relevant standards, which laid an excellent foundation for PG-based ecological restoration materials and filling materials, with low economic cost, simple process and strong feasibility. This will provide great convenience for the later mining and metallurgy.

Proximate Composition and Sensory Evaluation Between Artificially Ripened and Naturally Ripened Pineapples (Ananas comosus)

The number of artificially ripened pineapples is outnumbered than the naturally ripened pineapples. However, there is a lack of understanding between artificially ripened and naturally ripened pineapples. Thus the inquiry was anticipated to explore the physicochemical changes and organoleptic acceptability of the naturally ripened and artificially ripened pineapples. Farmers used different chemicals such as calcium carbide, ethylene, besides growth hormones to reduce production loss. Here we evaluated the content of moisture, ash, protein, fat, crude fiber, reducing sugar, total sugar, titratable acidity, sucrose, and vitamin C in both naturally ripened and artificially ripened pineapples. Artificially ripened pineapples showed a significantly lower vitamin C than naturally ripened ones, but arsenic content was nil in both samples. In the case of color and appearance, there was no significant difference between the two samples, but in case of the other organoleptic properties, such as flavor, sweetness, sourness, the natural one was more acceptable. Thus naturally ripened pineapples are more beneficial to consumers than artificially ripened ones.

Durability Performance of Self-Compacting Concrete Containing Crumb Rubber, Fly Ash and Calcium Carbide Waste

Waste tire disposal continues to pose a threat to the environment due to its non-biodegradable nature. Therefore, some means of managing waste tires include grinding them to crumb rubber (CR) sizes and using them as a partial replacement to fine aggregate in concrete. However, the use of CR has a series of advantages, but its major disadvantage is strength reduction. This leads to the utilization of calcium carbide waste (CCW) to mitigate the negative effect of CR in self-compacting concrete (SCC). This study investigates the durability properties of SCC containing CR modified using fly ash and CCW. The durability properties considered are water absorption, acid attack, salt resistance, and elevated temperature of the mixes. The experiment was conducted for mixes with no-fly ash content and their replica mixes containing fly ash to replace 40% of the cement. In the mixes, CR was used to partially replace fine aggregate in proportions of 0%, 10%, and 20% by volume, and CCW was used as a partial replacement to cement at 0%, 5%, and 10% by volume. The results indicate that the mixes containing fly ash had higher resistance to acid (H2SO4) and salt (MgSO4), with up to 23% resistance observed when compared to the mix containing no fly ash. In addition, resistance to acid attack decreased with the increase in the replacement of fine aggregate with CR. The same principle applied to the salt attack scenario, although the rate was more rapid with the acid than the salt. The results obtained from heating indicate that the weight loss was reduced slightly with the increase in CCW, and was increased with the increase in CR and temperature. Similarly, the compressive strength was observed to slightly increase at room temperature (27 °C) and the greatest loss in compressive strength was observed between the temperature of 300 and 400 °C. However, highest water absorption, of 2.83%, was observed in the mix containing 20% CR, and 0% CCW, while the lowest water absorption, of 1.68%, was found in the mix with 0% CR, 40% fly ash, and 10% CCW. In conclusion, fly ash is recommended for concrete structures immersed in water, acid, or salt in sulphate- and magnesium-prone areas; conversely, fly ash and CR reduce the resistance of SCC to heat beyond 200 °C.

Mechanochemical Synthesis of Diarylethynes from Aryl Iodides and CaC2

A mechanochemical synthesis of diarylethynes from aryl iodides and calcium carbide as acetylene source is reported. The reaction is catalyzed by a palladium catalyst in the presence of copper salt, base and ethanol as liquid assisting grinding (LAG) additive. Various aryl and heteroaryl iodides have been converted in up to excellent yields.

Equivalent CO2 Emission and Cost Analysis of Green Self-Compacting Rubberized Concrete

Global warming and climate changes are the major environmental challenges globally. With CO2 emission being one of the main greenhouse gases emitted to the environment, and cement and concrete production amounting to about 10% of the global CO2 emission, there is a need for the construction industry to utilize an environmentally sustainable material as an alternative to cement. This study analyzed the cost, CO2 emission and strength properties of green self-compacting concrete (SCC) ternary blend containing fly ash, calcium carbide residue (CCR), and crumb rubber (CR) as a replacement material by volume of cement, cementitious material, and fine aggregate, respectively. Cement was replaced with fly ash at 0 and 40% by volume. CCR was used as a replacement at 5 and 10% by volume of cementitious materials, CR replaced fine aggregate in proportions of 10 and 20% by volume. The result indicated that the mix with 0% fly ash and 20% CR replacement of fine aggregate was the most expensive and had the highest CO2 emission. However, the mix with 10% CR, 40% fly ash, and 10% CCR had the lowest CO2 emission and was therefore the greenest SCC mix. The 28-day maximum compressive strength of 45 MPa was achieved in a mix with 0% CR, 0% fly ash, and 10% CCR, while the utmost 28-day splitting tensile strength of 4.1 MPa was achieved with a mix with 10% CR, 0% fly ash, and 5% CCR, and the highest flexural strength at 28 days was 6.7 MPa and was also obtained in a mix with 0% CR, 0% fly ash, and 5% CCR. In conclusion, a green SCC can be produced by substituting 40% cement with fly ash, 10% fine aggregate with CR, and 10% CCR as a replacement by volume of cementitious material, which is highly affordable and has an acceptable strength as recommended for conventional SCC.