# ZnO/SnO2 nanocomposite removes 98.07% of alizarine yellow R dye from water in 60 minutes under visible light

- Published: 2026-11-13 14:24 UTC
- Section: Planet › Ecology & recycling
- Tags: ZnO/SnO2 nanocomposite, alizarine yellow R, photocatalytic degradation, visible light photocatalyst, azo dye removal, wastewater treatment, hydrothermal synthesis, heterojunction, bandgap, BMC Chemistry
- URL: https://realtech.media/news/rt-e33a72a89ade4e9ef26a7b3c_zno_sno2_nanocomposite/

**In laboratory tests, a ZnO/SnO2 photocatalyst degraded 98.07% of a toxic azo dye in aqueous solution, versus 63.10% for ZnO and 52.47% for SnO2 alone.**

![ZnO/SnO2 nanocomposite removes 98.07% of alizarine yellow R dye from water in 60 minutes under visible light](https://realtech.media/media/2026/11/91b25e9203d29a3f.jpg)
*Professorcornbread, Wikimedia Commons, CC BY-SA 4.0*

A research team has synthesized a zinc oxide/tin dioxide (ZnO/SnO2) nanocomposite photocatalyst and tested it on the toxic azo dye alizarine yellow R (AYR) in aqueous solution. According to the study in BMC Chemistry, the material degraded 98.07% of the dye in 60 minutes under visible light at optimal conditions. Pure ZnO and pure SnO2 reached 63.10% and 52.47% over the same period [1].

AYR is a water-soluble azo dye derived from salicylic acid. Its aromatic rings and azo bonds make it resistant to microbial breakdown, heat and light, so it persists in water. Pure ZnO and SnO2 have wide bandgaps and mainly absorb ultraviolet light, and their charge carriers recombine quickly.

## Synthesis and characterization

The composite was made by a hydrothermal method combined with ultrasonic-assisted calcination. ZnO and SnO2 were prepared separately, with autoclaving at 180 °C for 24 hours in each case, then mixed 1:1 by mass, ultrasonicated for two hours, dried at 80 °C and calcined at 350 °C for two hours [1].

X-ray diffraction showed peaks of both oxides with no extra phases. Electron microscopy showed aggregated particles of irregular shape, and EDS mapping showed uniform element distribution: 58.9% oxygen, 24.6% zinc and 16.5% tin (atomic). XPS confirmed zinc in the divalent state and tin in the tetravalent state. The specific surface area was 39.58 m²/g, which the authors consider moderate and not the main reason for the activity [1].

## Degradation performance

The optical bandgap of the composite was 3.19 eV, against 3.24 eV for ZnO and 3.31 eV for SnO2, and its absorption edge shifted to 402 nm. According to the authors, this increased visible light absorption [1].

Tests used a 500 mL vessel and a 350 W xenon lamp. Optimal conditions were 32 mg of catalyst, 24 ppm initial dye, pH 5 and 30 °C. Without a catalyst, 4.30% of the dye degraded. The reaction followed pseudo-first-order kinetics with a rate constant of 0.0651 min⁻¹ for the composite, versus 0.0170 min⁻¹ for ZnO and 0.0125 min⁻¹ for SnO2 [1].

Raising the catalyst dose from 8 to 32 mg increased removal from 47.69% to 98.07%; at 40 and 48 mg it fell to 94.54% and 89.38%, which the authors attribute to particle aggregation and light scattering. Degradation also peaked at 24 ppm dye and dropped at 30 and 36 ppm. Radical scavenging experiments confirmed the involvement of reactive radicals. The catalyst kept its effectiveness over five consecutive cycles [1].

## Sources

1. [BMC Chemistry](https://doi.org/10.1186/s13065-026-01907-w)
2. [bioengineer.org](https://bioengineer.org/zinc-and-tin-oxide-nanocomposite-degrades-alizarine-yellow-r-dye-under-visible-light)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-e33a72a89ade4e9ef26a7b3c_zno_sno2_nanocomposite/