A new application, the same concept of circular development
Z-ONA4LIFE is building a technology facility for transforming hazardous aluminium salt slag into high-value synthetic zeolite. This new zeolite is already being tested against mining effluents, leachates, livestock waste, and gas streams. The study “Adsorption of Safranine-T dye using a waste-based zeolite: Optimization, kinetic and isothermal study”, co-authored by Z-ONA4LIFE partners from CSIC, adds effluents from textile industry to that list.
The study demonstrates that an aluminium waste-based LTA zeolite removes Safranine-T (ST) textile dye at 98.12% efficiency in just one minute, without requiring any pH adjustment, since textile wastewaters are naturally alkaline. The authors frame this as a “symbiosis” between two polluting sectors: the aluminium industry and the textile industry.
The textile industry generates approximately 200 billion litres of dye-containing effluent annually, losing 280,000 tonnes of dyes into aquatic ecosystems every year. Conventional treatment methods are costly, generate secondary pollutants, and struggle with ST’s structural complexity. Until now, no study had explored zeolite from aluminium waste for this application.
This study enables waste generated by the aluminium industry to be transformed into a valuable product, namely zeolite, which is then used to decontaminate effluent from the textile industry.
Study results
The key findings from the paper are summarised below.
- Removal efficiency: 98.12%. What makes this especially striking is the speed: virtually all of that removal happened within the first minute of contact. After that, performance stayed. For an industrial treatment process, this is ideal: fast, predictable, and consistent.
- How the zeolite captures the dye: the zeolite works like a sponge with a naturally charged surface. Because Safranine-T dye carries a positive electrical charge, it is linked onto the negatively charged surface of the zeolite. Importantly, this attachment is reversible (scientists call it “physisorption”), meaning the dye molecules sit on the surface rather than bonding to it permanently. This matters because it makes the zeolite easy to clean and reuse: the captured dye can be washed off, the zeolite is restored, and the recovered dye may itself be recycled.
- The process is self-sustaining - no extra energy needed: laboratory tests at different temperatures confirmed that the dye removal happens spontaneously. In plain terms: the system does not need external added energy, the process is spontaneous and it works at room temperature. This is an important advantage for large-scale industrial use, where energy costs matter.
- Outperforming all other zeolites tested: the aluminium waste-based LTA zeolite was compared side-by-side with three alternatives under identical conditions. It came out on top in every case: removing 98.12% of the dye, compared to 94.40% for an aluminium waste-derived NaP zeolite, 93.11% for a natural zeolite (mordenite), and 82.95% for a synthetic and commercialLTA zeolite. The reason why the waste-based zeolite developed in this research performs better is straightforward: it has a larger specific surface area than those for the other zeolites studied. More surface means more capacity to capture contaminants.
“The aluminium waste-based LTA zeolite demonstrated a removal capacity even higher than the synthetic and commercial LTA zeolite — a highly promising result that can significantly contribute to sustainability and the circular economy.”
Next steps within Z-ONA4LIFE
This study establishes a new application sector for the Z-ONA zeolite. Forthcoming work will develop a pilot-scale continuous-flow process for the use of Z-ONA zeolite in the treatment of contaminated effluent.
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