# Characterization and Surface Study of Volcanic Ashes from Popocatépetl

## TL;DR

Volcanic ash from Popocatépetl can effectively remove methylene blue dye from water without needing extra treatment.

## Contribution

First use of Popocatépetl volcanic ash as a natural adsorbent for methylene blue dye removal.

## Key findings

- Volcanic ash achieved a maximum adsorption capacity of 3.46 mg/g for methylene blue.
- The Langmuir isotherm model showed strong correlation (R² = 0.99351) indicating monolayer adsorption.
- Adsorption kinetics followed a pseudo-first-order model with k = 8.02 × 10⁻³ min⁻¹.

## Abstract

Puebla City, Mexico, experienced several volcanic ash
storms that
polluted the city and its surroundings. The spectroscopic characterization
of the volcanic ashes is reported in more detail herein using IR,
ESR, SEM, and powder diffraction X-ray. We report for the first time
the use of volcanic ashes from Popocatépetl, a natural material,
functioning as an adsorbent for removal of the cationic dye methylene
blue from aqueous media. Batch adsorption experiments were conducted
under varying initial dye concentrations and contact times to describe
the adsorption behavior of the ashes, was obtained a SSA = 0.7245
m2/g. The equilibrium data were fitted to the Langmuir
and Freundlich isotherm models. The Langmuir model exhibited a strong
correlation (R
2 = 0.99351) that suggested
monolayer adsorption on a homogeneous surface with a maximum adsorption
capacity of q
max 3.46 mg/g. These findings
support the notion that volcanic ash can act as a natural alternative
adsorbent. The value of a pseudo-first-order kinetic constant k = 8.02 × 10–3 min–1 (R
2 = 0.99489) was obtained by batch
equilibrium adsorption experiments when 40 mg/L of MB was used. This
value, along with q
max, is similar to
activated carbon products from seeds. Remarkably though, adsorption
by volcanic ashes did not require any additional treatment, unlike
current carbon-based products.