Green Carbon Dot Nanofibers Pull Toxic Crystal Violet Dye Out of Wastewater

A team of chemists at Shahid Beheshti University in Tehran has developed a remarkably simple yet powerful material for cleaning dye-polluted water: ultrathin nanofibers spun from polyvinyl alcohol and gum arabic, studded with glowing green carbon dots. Writing in Environmental Science and Pollution Research, Amir Safaei, Farshad Giyahban, and Homeira Ebrahimzadeh describe how this fully green composite efficiently strips crystal violet, a stubborn cationic dye, from aqueous media, and how it can be regenerated and reused cycle after cycle without losing its appetite for the pollutant.

Crystal violet is not merely a cosmetic nuisance. The triarylmethane dye, widely used in textile printing, paper production, and even as a biological stain, is toxic to aquatic life and suspected of harmful effects in humans, which is why researchers worldwide are racing to find cheap, sustainable ways to capture it before it reaches rivers and groundwater. Adsorption, the process by which dye molecules cling to the surface of a solid material, remains one of the most practical removal strategies, but the performance of any adsorbent depends heavily on how much accessible surface it offers.

That is where electrospinning comes in. The technique applies a high voltage to a droplet of polymer solution, stretching it into a whip-like jet that whips through the air, solvent evaporating along the way, until it lands as fibers with diameters measured in nanometers. Because these fibers pack enormous surface area and high porosity into a small mass of material, they expose a vast number of adsorption sites to the surrounding water. The Iranian team exploited this by blending polyvinyl alcohol, a water-friendly synthetic polymer, with gum arabic, a natural exudate from acacia trees prized for its biocompatibility and abundance of functional groups.

The twist in this study is the addition of carbon dots, nanoscale carbon-based particles that have attracted enormous interest for their fluorescence, low toxicity, and ease of green synthesis. Embedded within the electrospun nanofiber matrix, the carbon dots contribute additional interaction sites and functional chemistry that boost the composite’s ability to bind positively charged crystal violet molecules. The researchers prepared the composite solution and spun it directly into the final adsorbent, avoiding harsh chemicals and keeping the entire fabrication route aligned with green chemistry principles.

To confirm that the material was what they intended, the authors subjected it to a battery of characterization techniques. Fourier transform infrared spectroscopy mapped the chemical bonds and functional groups present in the fibers, verifying that the polymer, gum, and carbon dot components were integrated. X-ray diffraction probed the internal structure, while scanning electron microscopy revealed the fibrous morphology, showing the continuous, porous network that gives the material its high surface area. Energy dispersive X-ray analysis confirmed the elemental composition, and transmission electron microscopy allowed the team to visualize the nanoscale architecture, including the distribution of carbon dots within the fibers.

With the adsorbent in hand, the group systematically tested how well it captured crystal violet from water and, just as importantly, how the process worked. Adsorption kinetics were evaluated using three classical models: pseudo-first-order, pseudo-second-order, and intraparticle diffusion. The data aligned best with the pseudo-second-order model, a result with real mechanistic meaning, since it indicates that the rate-limiting step involves chemical interactions, such as electron sharing or electrostatic attraction, between the dye molecules and the binding sites on the fiber surface, rather than simple physical deposition.

The equilibrium behavior told a complementary story. When the team fitted their adsorption data to the Langmuir, Freundlich, and Temkin isotherm models, the Langmuir model provided the best description. That outcome implies that crystal violet molecules occupy a finite set of energetically equivalent sites on the nanofiber surface, forming at most a single molecular layer, and that once a site is filled it can no longer accept another dye molecule. Such monolayer adsorption on a uniform surface is exactly what one hopes for in a well-behaved, predictable adsorbent, making it easier to design treatment systems around the material.

Thermodynamic analysis added further insight into the driving forces at play. The results showed that the adsorption process is spontaneous and exothermic, meaning it proceeds willingly at the tested conditions and releases heat as the dye binds. An exothermic signature typically points to physical and electrostatic interactions dominating the uptake and suggests that lower temperatures favor adsorption, information that matters when engineers consider real-world wastewater streams whose temperatures vary with season and location.

Perhaps the most encouraging finding for practical deployment came from the reusability tests. Many promising adsorbents falter in regeneration, losing capacity after a handful of cycles as their binding sites clog or their structure degrades. The carbon dot-embedded PVA/gum arabic nanofibers, by contrast, demonstrated high recoverability with no considerable loss in adsorption performance over six consecutive adsorption-desorption cycles. That durability addresses one of the biggest economic hurdles for nanomaterial-based water treatment, since a sorbent that must be replaced after every use quickly becomes prohibitively expensive.

The study sits within a broader surge of interest in biopolymer-based electrospun adsorbents, from gum-based fibers explored for food packaging to hydrogels and aerogels built from chitosan, alginate, and cellulose for capturing dyes, heavy metals, and pharmaceuticals. What distinguishes this work is the combination of three benign ingredients, a scalable fiber fabrication method, and rigorous kinetic, isotherm, and thermodynamic modeling that together demonstrate a coherent, sustainable package. As textile industries in water-stressed regions face tightening discharge rules, materials like these green nanofibers could offer a route to cleaner effluent that does not trade one environmental problem for another, turning tree sap, a common polymer, and carbon nanodots into an effective filter for one of the dye industry’s most persistent pollutants.

Subject of Research: Green carbon dot-embedded electrospun PVA/gum arabic nanofibers for adsorptive removal of crystal violet dye from water

Article Title: Green carbon dot–embedded Electrospun PVA/gum arabic nanofibers for efficient crystal violet removal from aqueous media

Article References: Safaei, A., Giyahban, F., & Ebrahimzadeh, H. (2026). Green carbon dot–embedded Electrospun PVA/gum arabic nanofibers for efficient crystal violet removal from aqueous media. Environmental Science and Pollution Research, 33(30), 15784-15798. https://doi.org/10.1007/s11356-026-38234-5

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38234-5

Keywords: carbon dots, electrospun nanofibers, gum arabic, polyvinyl alcohol, crystal violet, dye removal, adsorption, wastewater treatment, Langmuir isotherm, pseudo-second-order kinetics, green adsorbent, water purification