Waste, Volume 2, Issue 4 (December 2024) – 4 articles

The main thrust of the current study is to examine the effects of ground granulated blast-furnace slag (GGBS), pulverized fuel ash (PFA), and bi-combination of GGBS and PFA on the mechanical properties of concrete. Seven concrete mixes were carried out in this study; including the control mix and the other six mixes had supplementary cementitious materials (GGBS, and PFA) as partial replacement of Portland cement at different replacement levels. The physical properties, oxides, and chemical composition of OPC, GGBS and PFA were experimentally investigated. The workability of the fresh concrete mixes was carried out by means of slump test and compaction index test. This study also examined the compressive strength of the different concrete mixes at different curing ages along with the splitting tensile strength. Cost analysis and the environmental impact of the different concrete mixes was also evaluated. The study results showed that the workability was significantly improved through the replacement of cement with PFA and GGBS. The utilisation of fly ash at 30% replacement level achieved the highest workability. The highest compressive strength was achieved by concrete mixes replacing 30% GGBS with cement, and a bi-combination of 10% PFA and 20% GGBS. The results also showed that the bi-combination of fly ash and GGBS at 10% and 20% replacement level was found to be favorable in terms of both cost and environmental impact. Full article

Lignocellulosic biomass, including agricultural, forestry, and energy crop waste, is one of Earth’s most abundant renewable resources, accounting for approximately 50% of global renewable resources. It contains cellulose, hemicellulose, and lignin, making it crucial for biofuels and bio-based chemicals. Due to its complex structure, single-pretreatment methods are inefficient, leading to the development of combined pretreatment technologies. These methods enhance cellulose accessibility and conversion efficiency. This paper analyzes the principles, advantages, and disadvantages of various combined pretreatment methods and their practical benefits. It highlights recent research achievements and applications in biofuel, biochemical production, and feed. By integrating multiple pretreatment methods, biomass degradation efficiency can be significantly improved, energy consumption reduced, and chemical reagent use minimized. Future advancements in combined physical, chemical, and biological pretreatment technologies will further enhance biomass utilization efficiency, reduce energy consumption, and protect the environment, providing robust support for sustainable renewable energy development and ecological protection. Full article

This study examines recovery efforts at Gran Tarajal Harbor following a significant oil spill, employing a combination of innovative technologies tailored to enhance oil spill remediation. Cleanup operations incorporated advanced absorbent sponges with high reusability, absorbent granulates for targeted hydrocarbon capture, bioremediation techniques using allochthonous microorganisms to accelerate natural degradation processes, and the integration of newly designed oil containment barriers coupled with sponges. These technologies were instrumental in effectively mitigating environmental damage, as evidenced by a reduction in hydrocarbon concentrations in sediments from nearly 60,000 mg/kg to under 1600 mg/kg within seven months. Notably, advanced absorbent sponges demonstrated superior capacity for repeated use, optimizing the cleanup process and contributing to the sustainability of the response efforts. The most important finding of this research is the demonstrated efficacy of integrated approach in not only reducing hydrocarbon contamination but also in promoting ecological recovery. Heavy metal analyses revealed that lead and copper concentrations were primarily associated with routine port activities, while mercury levels, attributed to the spill, decreased significantly over time. Tissue analysis of local organisms showed minimal contamination, and assessments of biological communities indicated signs of ecological recovery. This work highlights the necessity of introduce new disruptive technologies in contingency plans. Full article

An investigation has been carried out to understand the solution chemistry of the Cu-NH⁻-SO₄⁻² system, focusing on the effect of pH on the solubility of copper in the solution and maximizing the Cu(I):Cu(II) ratio. A Pourbaix diagram for the Cu-N-S system has also been created using the HSC Chemistry software for a wide range of Cu-NH₃ species, unlike most other studies that focused only on Cu(NH₃)₄²⁺ and Cu(NH₃)₅²⁺ (Cu(II)) as the dominant species. The Pourbaix diagram demonstrated that the Cu(I) exists as Cu(NH₃)₂⁺, while the Cu(II) species are present in the system as Cu(NH₃)₄²⁺ and Cu(NH₃)₅²⁺, depending upon the Eh and pH of the solution. Copper precipitation was observed in the electrolyte at pH values less than 8.0, and the precipitation behavior increased as the pH became acidic. The highest Cu(I):Cu(II) ratio was observed at higher pH values of 10.05 due to the higher solubility of copper at higher alkaline pH. The maximum Cu(II) concentration can be achieved at 4.0 M NH₄OH and 0.76 M (NH₄)₂SO₄. In the case of low pH, the highest Cu(I):Cu(II) ratio obtained was 0.91 against the 4.0 M and 0.25 M concentrations of NH₄OH and (NH₄)₂SO₄, respectively. Meanwhile, at high pH, the maximum Cu(I):Cu(II) ratio was 15.11 against the 0.25 M (NH₄)₂SO₄ and 4.0 M NH₄OH. Furthermore, the low pH experiments showed the equilibrium constant (K) K < 1, and the high pH experiments demonstrated K > 1, which justified the lower and higher copper concentrations in the solution, respectively. Full article