Physchem

This study investigates the acid dyeing of Polyamide 6 (PA6) fabric by comparing conventional heating and microwave-assisted techniques. The influence of critical process parameters—namely pH, temperature, dyeing time, and dye concentration—on color strength (K/S) was systematically evaluated using C.I. Acid Blue 324. Results indicated an inverse correlation between pH and K/S for both methods, with the maximum color yield achieved at pH 3.0. While dye uptake improved with increasing temperature, time, and concentration in both systems, the microwave-assisted approach (160 W) significantly accelerated the process. Optimal conditions for conventional dyeing were established at pH 3, 95 °C, and a 30 min reaction time with 1.5% dye concentration. In contrast, the microwave-assisted process reached equivalent exhaustion levels in only 10 min under otherwise identical conditions. The findings confirm that microwave-assisted dyeing is a rapid, energy-efficient, and sustainable alternative for PA6 processing, offering substantial reductions in production time.

One thermodynamic parameter that is crucial to heat transport within the fluidized bed inside the rotary kiln, during clinker production, is the specific heat capacity. The particular parameter is often considered constant in the open literature, while, in reality, it strongly depends on the fluidized bed’s temperature and composition, considering that the temperature inside the kiln ranges from approx. 800 K up to 2000 K. For the current study, a mixing rule reported in the literature was applied in order to calculate the C_p of the fluidized bed, utilizing temperature and composition profiles available in the literature. An in-house code was developed for the comparison of the literature-reported C_ps and those resulting from the mixing rule. It was discovered that the C_p of the fluidized bed had a proportional increase with the increase in the temperature along the length of the kiln. The deviation between the two values (calculated and literature) is relatively small in some cases, whereas, in others, it is quite significant, ranging from 1.56% to 52.49%, thus making the adoption of the temperature-dependence of C_p necessary. Establishing a more accurate relation for the specific heat capacity leads to a better energy balance inside the kiln, which, along with other improvements, can lead to a decrease in the energy consumed and a significant reduction in greenhouse gas emissions.

In regions with abundant solar energy, solar water disinfection (SODIS) offers a sustainable strategy to improve drinking water access, especially in rural, off-grid communities. This study presents a numerical modeling approach to assess the thermal and microbial disinfection performance of glass-free parabolic trough collectors (PTCs). The model integrates geometric sizing, one-dimensional thermal energy balance, and first-order microbial inactivation kinetics, supported by optical simulations in SolTRACE 3.0. Simulations applied to a representative case in the Colombian Caribbean (Gambote, Bolívar) highlight the influence of rim angle, focal length, and optical properties on system efficiency. Results show that compact PTCs can achieve fluid temperatures above 70 °C and effective pathogen inactivation within short exposure times. Sensitivity analysis identifies key geometric and environmental factors that optimize performance under variable conditions. The model provides a practical tool for guiding the design and local adaptation of SODIS systems, supporting decentralized, low-cost water treatment solutions aligned with sustainable development goals. Furthermore, it offers a framework for future assessments of PTC implementations in different climatic scenarios.