Biochar, a carbon-rich material produced from agricultural residues, forestry waste, manure, sludge, and other biomass, has attracted growing interest as an affordable material for water purification. Its porous structure and chemically active surface can capture contaminants, while its production can transform discarded biomass into a useful environmental resource.
However, unmodified biochar is not a universal solution. It may have insufficient adsorption capacity, limited selectivity for certain emerging pollutants, and a powder-like form that is difficult to recover from treated water.
A new review published in Sustainable Carbon Materials shows how researchers are engineering biochar-based composites to overcome these limitations, while warning that improved performance must not come at the cost of new environmental risks.
"Biochar composites should not be designed only to remove more pollutants. They must also remain stable, recoverable, energy-efficient, and environmentally safe throughout their entire life cycle," said corresponding author Cui Wang of Chang'an University. "Our review provides a framework for evaluating these materials according to both treatment performance and their true net environmental benefit."
The authors examined how the choice of biomass feedstock, carbonization method, temperature, atmosphere, and modification strategy influences biochar's pore structure, surface chemistry, electrical properties, and pollutant-removal performance.
They focused on three major groups of engineered materials: magnetic biochar, metal oxide or hydroxide-modified biochar, and biochar coated with functional nanoparticles. Magnetic materials can allow used biochar to be separated from water with an external magnetic field. Metal oxides and other functional components can introduce highly active sites that improve adsorption, catalysis, and selectivity.
These composites can target conventional contaminants such as heavy metals, dyes, nitrogen, and phosphorus, as well as emerging pollutants including antibiotics, perfluorinated substances, and microplastics. Their removal mechanisms include pore filling, electrostatic attraction, ion exchange, surface complexation, hydrogen bonding, and interactions between aromatic structures. Some composites can also catalytically degrade pollutants instead of merely transferring them from water onto a solid material.
The review identifies a central challenge: the modifications that improve treatment efficiency may also increase energy use, production complexity, chemical consumption, nanoparticle leakage, and secondary pollution risks. Active components can detach during use, pores can become blocked, and exhausted materials may release accumulated pollutants if they are not properly regenerated or disposed of.
The authors therefore call for research to move beyond laboratory tests conducted with single pollutants under idealized conditions. Materials should be evaluated in real wastewater, where salts, organic matter, competing contaminants, and changing pH can alter performance.
They also recommend standardized testing of adsorption, catalytic activity, regeneration, long-term stability, leaching, ecotoxicity, and environmental footprint. A cradle-to-grave life-cycle assessment should examine impacts from feedstock collection and material production through repeated use and final disposal.
The researchers highlight Safe and Sustainable by Design as a promising approach for balancing function, safety, and sustainability before a composite is produced at scale. Green synthesis, low-energy modification, durable chemical bonding, and application-specific design could help prevent pollution rather than addressing risks only after deployment.
By connecting material preparation, pollutant-removal mechanisms, practical performance, and environmental risk, the review offers a roadmap for moving biochar-based composites from promising laboratory materials toward reliable wastewater-treatment systems.
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Journal reference: Wang C, Hou Q, Zhang X, Bai B. 2026. Preparation of biochar-based composites and application in removal of conventional and emerging pollutants from wastewater: performance enhancement, mechanisms, sustainability, and risk evaluations. Sustainable Carbon Materials 2: e020 doi: 10.48130/scm-0026-0015
https://www.maxapress.com/article/doi/10.48130/scm-0026-0015
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About Sustainable Carbon Materials :
Sustainable Carbon Materials (e-ISSN 3070-3557) is a multidisciplinary platform for communicating advances in fundamental and applied research on carbon-based materials. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon materials around the world to deliver findings from this rapidly expanding field of science. It is a peer-reviewed, open-access journal that publishes review, original research, invited review, rapid report, perspective, commentary and correspondence papers.
