📄 chemistry

Natural-based biocomposites of chitosan, β-cyclodextrin, and potato peel waste for the adsorptive removal of sunset yellow and diclofenac

This study demonstrates that sustainable biocomposites synthesized from potato peel waste, chitosan, and β-cyclodextrin effectively remove Sunset Yellow and diclofenac from aqueous solutions, with the BC-5 formulation achieving a maximum adsorption capacity of 221.89 mg g⁻¹ at pH 4 while exhibiting excellent reusability.

Original authors: Nathália Favarin da Silva, Sonia Jemli, Larissa Crestani, Franciele da Silva Bruckmann, Fakhreddine Ben Amara, Luis Felipe Oliveira Silva, Tito José Crissien, Evandro Stoffels Mallmann, Guilherme Luiz

Published 2026-07-03

📖 4 min read☕ Coffee break read

CC BY 4.0

Original authors: Nathália Favarin da Silva, Sonia Jemli, Larissa Crestani, Franciele da Silva Bruckmann, Fakhreddine Ben Amara, Luis Felipe Oliveira Silva, Tito José Crissien, Evandro Stoffels Mallmann, Guilherme Luiz Dotto

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine your local water supply is like a giant, clear swimming pool. Unfortunately, someone has accidentally dumped two very stubborn, unwanted guests into it: a bright yellow food coloring (Sunset Yellow) and a common painkiller (Diclofenac). These aren't just floating around; they are "sticky" and hard to get rid of, and they can be harmful to fish and people if left alone.

Scientists usually try to filter these out, but standard filters often clog up, cost a fortune, or leave some of the bad stuff behind. So, a team of researchers from Brazil, Tunisia, and Colombia decided to build a custom "super-sponge" using things that would otherwise be thrown in the trash.

The Recipe: Turning Trash into Treasure

Instead of buying expensive chemicals, the team cooked up a new material using three ingredients:

Potato Peels: The leftover skins from making french fries (which they turned into a fine powder).
Chitosan: A natural, gooey substance found in shrimp shells (think of it as nature's glue).
Beta-Cyclodextrin: A special ring-shaped molecule made from the starch in those same potato peels.

They mixed these three ingredients together with a little bit of citric acid (like lemon juice) and baked them. The result was a series of seven different "biocomposites" (let's call them BC-1 through BC-7), each with a slightly different recipe.

The "Goldilocks" Sponge

The researchers tested all seven versions to see which one was the best at catching the yellow dye and the painkiller. They found that BC-5 was the "Goldilocks" sponge—it wasn't too much of one ingredient and not too little of another. It had just the right amount of potato powder and chitosan to work perfectly.

Why did BC-5 win?
Think of the chitosan as having tiny, positively charged "Velcro hooks" on its surface. The yellow dye and the painkiller are negatively charged (like magnets with opposite poles). When the water flows over the sponge, the dye and medicine get stuck to the hooks. The potato powder acts like the sturdy frame of the sponge, holding everything together, while the ring-shaped molecules act like little pockets that can grab onto the medicine molecules specifically.

The Results: Catching the Contaminants

The Sweet Spot: The sponge worked best when the water was slightly acidic (like lemonade, pH 4). In this environment, the "Velcro hooks" on the sponge were fully charged and ready to grab the contaminants. If the water was too soapy (alkaline), the hooks lost their charge, and the sponge stopped working.
Speed: The sponge grabbed the contaminants very quickly, doing most of the work in the first hour.
Capacity: The BC-5 sponge was incredibly strong. It could hold onto 221 mg of yellow dye and 151 mg of painkiller for every single gram of sponge. To put that in perspective, a single gram of this sponge (about the size of a paperclip) could clean a significant amount of polluted water.
Reusability: The best part? The sponge didn't get tired. After it got full, the scientists washed it with a mild cleaning solution (sodium hydroxide), which made the "Velcro hooks" let go of the dirt. The sponge could then be dried and used again. It worked well for 5 cycles with the dye and 4 cycles with the painkiller before it started to lose a little bit of its power.

The Big Picture

The paper concludes that this new material is a "win-win." It takes waste (potato peels) that would go to a landfill, turns it into a high-tech cleaning tool, and does a better job than many expensive, man-made filters currently on the market. It's a simple, cheap, and eco-friendly way to scrub dangerous chemicals out of water, proving that sometimes the best solutions are hiding in our kitchen scraps.

Technical Summary: Natural-based Biocomposites for the Adsorptive Removal of Sunset Yellow and Diclofenac

Problem Statement
The study addresses the environmental challenge posed by emerging contaminants in aquatic systems, specifically the anionic azo dye Sunset Yellow (SY) and the non-steroidal anti-inflammatory drug diclofenac potassium (DCP). These substances exhibit high persistence, low biodegradability, and potential ecotoxicological effects, including bioaccumulation and harm to aquatic life. Conventional treatment methods often suffer from limitations such as high operational costs, the formation of toxic by-products, or insufficient efficiency for low-concentration pollutants. Consequently, there is a need for sustainable, low-cost, and efficient adsorbents capable of removing these specific contaminants from wastewater.

Methodology
The research focused on the synthesis and evaluation of hybrid biocomposites (BCs) derived from potato peel waste (PPW), $\beta$ -cyclodextrin ( $\beta$ -CD), and chitosan (CS).

Material Synthesis: Seven distinct biocomposites (BC-1 to BC-7) were prepared using varying weight ratios of PPW, $\beta$ -CD, and CS. The preparation involved mixing these components with anhydrous citric acid (crosslinker) and $KH_2PO_4$ (catalyst), followed by heating at 140 °C for 7 hours.
Characterization: The materials were analyzed using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) with Energy-Dispersive Spectroscopy (EDS), and Thermogravimetric Analysis (TGA). Notably, BET/BJH surface area analysis was omitted due to the thermal sensitivity of the materials.
Adsorption Experiments: Batch experiments were conducted to evaluate the removal of SY and DCP. Key variables included pH optimization (range 2.0–10.0), kinetic studies (up to 120 minutes), and equilibrium isotherms (concentrations up to 500 mg L $^{-1}$ for SY and 150 mg L $^{-1}$ for DCP).
Modeling and Reuse: Kinetic data were fitted to pseudo-first-order (PFO), pseudo-second-order (PSO), and general-order models. Equilibrium data were analyzed using Langmuir, Freundlich, Sips, and Hill models. The most efficient material, BC-5, underwent regeneration tests using 0.5 M NaOH for up to five consecutive cycles.

Key Contributions and Results

Material Characterization: Characterization confirmed the successful crosslinking of the three components. FTIR spectra indicated the formation of ester bonds and the presence of abundant –OH and –NH $_2$ groups. XRD analysis revealed that increasing chitosan content reduced the crystallinity of $\beta$ -CD, resulting in predominantly amorphous structures. SEM micrographs showed that BC-5 (containing a higher proportion of chitosan) possessed a granular structure with increased surface roughness, which is favorable for adsorption. TGA confirmed sufficient thermal stability for the application.
Optimal Conditions: For both SY and DCP, adsorption efficiency was highly dependent on pH, with optimal performance observed at pH 4.0. This is attributed to the protonation of chitosan amino groups (forming –NH $_3^+$ ), which facilitates electrostatic attraction with the anionic contaminants.
Adsorption Performance:
- Sunset Yellow (SY): The general-order kinetic model provided the best fit, while the Sips isotherm model best described the equilibrium data. BC-5 demonstrated the highest adsorption capacity among all tested materials, reaching 221.89 mg g $^{-1}$ .
- Diclofenac Potassium (DCP): The pseudo-second-order (PSO) model best described the kinetics, suggesting chemisorption or specific surface interactions. The Sips model again provided the best fit for isotherms, indicating cooperative adsorption behavior. BC-5 achieved a modeled maximum adsorption capacity of 151.1 mg g $^{-1}$ .
Regeneration: BC-5 exhibited good reusability. For SY, the material maintained stable performance over five cycles. For DCP, adsorption capacity increased during the first four cycles before declining in the fifth, likely due to the progressive reorganization of active sites and eventual partial exhaustion.

Significance and Claims
The paper claims that the synthesized biocomposites, particularly BC-5, represent a promising, sustainable, and low-cost alternative for wastewater treatment. The study highlights the synergistic integration of agro-industrial waste (potato peels) with functional biopolymers ( $\beta$ -CD and chitosan) to create effective adsorbents.

The authors assert that BC-5 offers competitive performance compared to more complex and expensive adsorbents reported in the literature (such as MOFs and functionalized graphene), while utilizing a simpler synthesis route. The material's ability to effectively remove both anionic dyes and persistent pharmaceuticals, combined with its regeneration potential, positions it as a viable option for the treatment of effluents containing these emerging contaminants. The work emphasizes the alignment of this approach with circular economy principles by valorizing potato peel waste.

The Recipe: Turning Trash into Treasure

The "Goldilocks" Sponge

The Results: Catching the Contaminants

The Big Picture

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