Design and optimization of a biochar-based hybrid adsorption–electrochemical capacitor for wastewater dye remediation

Project Abstract

This study reports the design and optimization of a biochar-based hybrid adsorption–electrochemical capacitor (HB-AC) aimed at efficient remediation of wastewater dyes while enabling energy storage in a single integrated system. Biochar derived from agricultural residue was synthesized under pyrolytic conditions and subsequently activated to enhance surface area, porosity, and functional group distribution. The resulting material was employed as a bifunctional electrode in a capacitive deionization-like configuration, paired with a complementary carbonaceous counter-electrode to form a symmetric or asymmetric HB-AC device. A multi-faceted optimization strategy was implemented, combining physicochemical characterization, electrochemical testing, charge–discharge cycling, and dye adsorption experiments to achieve synergistic performance in contaminant removal and energy storage. Characterization by BET surface area analysis, scanning/transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and Fourier-transform infrared spectroscopy revealed a hierarchical porosity with micro-, meso-, and macroporous networks that facilitate rapid dye diffusion and high charge storage. Point of zero charge measurements and zeta potential analysis illuminated dye–biochar interactions across a range of pH values representative of real wastewater streams. Electrochemical assessments demonstrated high specific capacitance, favorable rate capability, and robust cyclic stability, attributed to well-developed porosity and surface functionalization that promote faradaic pseudocapacitance alongside electric double-layer effects. The adsorption performance for commonly encountered dyes (e.g., methylene blue, reactive red, and congo red) was quantified under varying contact times, initial concentrations, and ionic strengths, yielding adsorption capacities exceeding conventional activated carbons and displaying appreciable selectivity for cationic dyes in mixed dye systems. Innovative elements of the HB-AC design include (i) integration of adsorption and charge storage in a single electrode architecture to reduce footprint and capital cost; (ii) optimization of biochar activation protocols to tailor pore structure and surface chemistry for enhanced dye sequestration and redox-active site density; (iii) investigation of operational regimes that balance adsorption equilibrium with electrical regeneration to maintain performance over multiple cycles; and (iv) development of a coupled kinetics–isotherm model that predicts dye removal efficiency and energy storage output as functions of flow rate, voltage window, and rotation of electrode polarity during regeneration steps. Results indicate that the HB-AC device achieves simultaneous dye removal and energy recovery with competitive capacitance values and high rate performance under realistic wastewater conditions. Regeneration processes recover a substantial fraction of adsorption capacity while preserving electrochemical activity, enabling sustained operation over extended cycles. The study also includes a life-cycle and techno-economic assessment to evaluate scalability, environmental impact, and potential integration into existing wastewater treatment trains. The findings provide a proof-of-concept for a sustainable, multifunctional treatment technology that leverages biochar’s abundance and tunable surface chemistry to address persistent dye pollution while contributing to energy storage objectives in water treatment infrastructure.

Project Overview

What This Project Is About

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A simple, practical exploration of using a charcoal-like material called biochar inside a device that combines adsorption (pulling dyes from water) with a tiny battery-like capacitor function (electrochemical energy storage). The project looks at how designing this hybrid system can remove dyes from wastewater while also storing electrical energy or enabling rapid dye capture cycling.

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The Problem It Addresses

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Dyes from textiles and industry are hard to remove with ordinary filters and can be toxic to aquatic life. Current methods may be costly or generate secondary waste. This project seeks a cheaper, dual-purpose approach that both cleans water and gives us a way to store energy or reuse the material quickly through repeated use.

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Objectives of the Project

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1. Assess how biochar can adsorb dye molecules from water.
2. Incorporate biochar into a capacitor-like setup to improve dye removal and potential energy storage.
3. Optimize material preparation (e.g., activation of biochar) for better performance.
4. Evaluate the performance under different water conditions (pH, dye concentration).
5. Measure durability over repeated adsorption–desorption cycles.

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What You Will Do Step by Step

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1) Review background literature on biochar and adsorption–electrochemical systems.

2) Prepare biochar and assemble the hybrid device.

3) Test dye uptake, measure changes in electrical characteristics, and monitor energy storage behavior.

4) Analyze data to find optimal preparation and operating conditions.

5) Assess reusability through multiple cycles and surface chemistry changes.

6) Discuss practicality and potential scale-up considerations.

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Expected Outcome

Anticipated results include higher dye removal efficiency with a stable, reusable hybrid system and insightful data on how biochar properties influence both adsorption and electrochemical performance. The project aims to show a feasible path toward cost-effective wastewater treatment with added material value.