Turning Camellia shell waste into a dual nutrient trap for wastewater cleanup
The study showed that the engineered material, named BC5-500, achieved strong adsorption performance, especially for phosphate, and maintained useful activity even after repeated reuse cycles and in real swine wastewater.
Nitrogen and phosphorus pollution remains a major environmental challenge because large inputs from fertilizers, domestic discharge, and industrial and agricultural wastewater can destabilize aquatic ecosystems and trigger eutrophication. Adsorption has become a widely studied treatment route because it is simple, fast, and efficient, while biochar is especially attractive due to its porous structure, surface functional groups, and tunable chemistry. Previous studies have improved nutrient capture by modifying biochar with metals such as magnesium, iron, and aluminum, but adsorption performance still varies widely with feedstock and modification method. In this context, calcium-based modification is especially promising because calcium is abundant, relatively safe, inexpensive, and has strong affinity for ammonium and phosphate. At the same time, the rapidly expanding Camellia oleifera industry generates large volumes of shell waste that are difficult to dispose of, creating a practical need to convert this residue into higher-value materials.
A study (DOI:10.48130/bchax-0026-0002) published in Biochar X on 30 January 2026 by Anping Wang’s & Jie Wang’s team, Guizhou Normal University & Qiandongnan Agriculture Science Institute, reports that Ca(OH)2-modified shell biochar can effectively remove ammonium and phosphate through different but complementary chemical pathways.
To create the adsorbent, the team first cleaned, dried, ground, and pyrolyzed Camellia oleifera shells at 500 °C to obtain the base biochar BC-500, then mixed it with calcium hydroxide, washed and dried the product, and subjected it to a second pyrolysis step to produce BC5-500. They screened nine modified biochars and found BC5-500 to be the best performer, reaching adsorption capacities of 26.66 mg·g−1 for ammonium and 186.18 mg·g−1 for phosphate in preliminary tests. The material was then characterized by SEM, BET surface area analysis, FT-IR, XRD, and XPS. These analyses showed that calcium modification roughened the biochar surface, increased pore volume and average pore diameter, introduced calcium-containing active phases, and created more reactive sites for nutrient capture. Adsorption tests further showed that ammonium uptake was favored under alkaline conditions, peaking at pH 11.0, while phosphate uptake was strongest in acidic conditions, peaking at pH 2.0. Kinetic modeling showed that both adsorption processes followed the pseudo-second-order model, indicating chemisorption-dominated behavior. Isotherm analysis suggested that ammonium adsorption involved both monolayer and multilayer behavior, whereas phosphate adsorption was better described by the Freundlich model, consistent with multilayer adsorption on a heterogeneous surface. Temperature experiments showed that phosphate adsorption declined as temperature increased, while ammonium adsorption first decreased and then rose at higher temperatures. Mechanistic evidence from FT-IR, XRD, and XPS indicated that ammonium removal was driven mainly by ion exchange, whereas phosphate removal relied on both ion exchange and, more importantly, calcium-phosphate precipitation, including formation of hydroxyapatite-like products. Reuse tests showed that the biochar still retained substantial adsorption after five cycles. In actual swine wastewater, ammonium removal was limited, likely because of low concentration and competition from coexisting contaminants, but phosphate removal remained highly effective, reaching 97.73%, demonstrating particular promise for phosphorus-rich waste streams.
Overall, the study presents a practical example of waste-to-resource engineering: an abundant agricultural by-product was converted into a functional adsorbent capable of targeting two problematic nutrients in polluted water. Although its phosphate removal was much stronger than its ammonium performance in complex real wastewater, the material combined affordability, reusability, mechanistic clarity, and applicability to livestock effluents. The work therefore offers a useful foundation for developing biochar-based nutrient management technologies that link agricultural residue utilization with cleaner water and more sustainable resource recovery.
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References
DOI
Original Source URL
https://doi.org/10.48130/bchax-0026-0002
Funding information
This work is supported by the project of the Guizhou Provincial Department of Science and Technology (Grant Nos Qiankehe Zhicheng [2023] 078, Qiankehe Jichu-ZK [2024] zhongdian 055, and Qiankehe Pingtai-KXJZ [2025] 023), and Projects of Forestry Research in Guizhou Province (Grant No. GUI[2022] TSLY07).
About Biochar X
Biochar X is an open access, online-only journal aims to transcend traditional disciplinary boundaries by providing a multidisciplinary platform for the exchange of cutting-edge research in both fundamental and applied aspects of biochar. The journal is dedicated to supporting the global biochar research community by offering an innovative, efficient, and professional outlet for sharing new findings and perspectives. Its core focus lies in the discovery of novel insights and the development of emerging applications in the rapidly growing field of biochar science.
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Ca(OH)2-modified Camellia oleifera shell biochar: preparation, characterization, and adsorption of NH4+ and PO43−
Turning orange waste into a fast, reusable dye trap for wastewater
Maximum Academic Press
The optimized material, Fe/Zn-OPBC500, reached an adsorption capacity of 237.53 mg g⁻¹ and removed 96.8% of the dye within 60 minutes. It also maintained strong performance after repeated reuse and under a broad range of pH and common ionic conditions.
Synthetic dyes remain a major challenge in industrial wastewater treatment because they are highly soluble, structurally stable, and difficult to degrade once released into aquatic systems. Among them, methylene blue is widely used in textiles, staining, indicators, and pharmaceuticals, making its removal environmentally important. Adsorption has emerged as one of the most practical treatment approaches because it is simple, cost-effective, and efficient, but conventional biochar often suffers from limited adsorption capacity and poor structural optimization. Previous work has shown that ZnCl₂ activation can improve pore development, while Fe-based modification can introduce reactive adsorption sites. However, single-modification strategies usually cannot optimize pore architecture and surface chemistry at the same time. This gap led the researchers to investigate whether co-activation with ZnCl₂ and FeCl₃ could produce a more effective orange peel-derived biochar for dye removal.
A study (DOI:10.48130/bchax-0026-0001) published in Biochar X on 30 January 2026 by Lei Zhang’s & Junkang Guo’s team, Shaanxi University of Science & Technology, reports that Fe/Zn co-modification of orange peel produced a biochar with markedly enhanced porosity, richer active surface chemistry, rapid and high-capacity methylene blue adsorption, and strong regeneration performance.
To build the adsorbent, the team first washed, dried, ground, and sieved orange peel, then impregnated the biomass with FeCl₃ and ZnCl₂ before pyrolyzing it under nitrogen at controlled temperatures. They compared materials prepared at 500 °C and 900 °C, along with unmodified controls, and then characterized the products using SEM, XRD, Raman spectroscopy, FTIR, XPS, and nitrogen physisorption. These analyses showed that the dual-activation strategy reconstructed the biochar into a three-dimensional hierarchical porous structure while introducing iron oxide species and preserving oxygen-containing functional groups. Compared with pristine biochar, the optimized Fe/Zn-OPBC500 displayed a 16.1-fold increase in specific surface area and a 5.7-fold rise in total pore volume, creating a structure better suited for mass transfer and dye capture. The adsorption experiments then linked structure to performance. Under standard conditions, Fe/Zn-OPBC500 achieved 194.5 mg g⁻¹ at the selected dosage and reached a 96.8% removal rate within 60 minutes, outperforming Fe/Zn-OPBC900 and the pristine samples. Kinetic modeling showed that adsorption followed a pseudo-second-order model, indicating chemisorption-dominated behavior, while isotherm fitting favored the Langmuir model, consistent with predominantly monolayer adsorption. The maximum adsorption capacity reached 237.53 mg g⁻¹, and thermodynamic analysis indicated that the process was spontaneous. Performance also remained strong across pH 3 to 11, with adsorption increasing as the surface became more negatively charged above the point of zero charge. Tests with coexisting ions showed that multivalent cations such as Fe³⁺ and Ca²⁺ interfered more strongly than Na⁺, while anions had weaker effects overall. In regeneration experiments, the material retained more than 100 mg g⁻¹ over seven cycles, confirming good operational stability. Post-adsorption spectroscopic analysis further revealed that methylene blue removal arose from multiple cooperating pathways, including electrostatic attraction, hydrogen bonding, π–π interactions, pore confinement, covalent amide-like bonding, and surface complexation with iron sites. Together, these results showed that the material’s performance did not depend on a single factor, but on the synergy between engineered pore structure and multifunctional surface chemistry.
Overall, the study shows that orange peel waste can be converted into a robust, reusable, and high-performance adsorbent for dye-contaminated water. By combining accessible feedstock, moderate-temperature synthesis, fast kinetics, strong capacity, and multicycle reuse, the work advances both wastewater treatment and agricultural waste valorization.
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References
DOI
Original Source URL
https://doi.org/10.48130/bchax-0026-0001
Funding information
This work was funded by the National Natural Science Foundation of China (42207464), Young Talent Fund of Xi'an Association for Science and Technology (959202413043), Natural Science Foundation of Shaanxi Provincial Department of Education (24JK0353), Key Research and Development Program of Shaanxi (2025SF-YBXM-511), and the Key Industrial Chain Project of Shaanxi Province (2024NC-ZDCYL-02-15).
About Biochar X
Biochar X is an open access, online-only journal aims to transcend traditional disciplinary boundaries by providing a multidisciplinary platform for the exchange of cutting-edge research in both fundamental and applied aspects of biochar. The journal is dedicated to supporting the global biochar research community by offering an innovative, efficient, and professional outlet for sharing new findings and perspectives. Its core focus lies in the discovery of novel insights and the development of emerging applications in the rapidly growing field of biochar science.
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Hierarchical porous biochar with Fe/Zn co-activation derived from orange waste: enhanced methylene blue adsorption and mechanistic insights
Internal-heating pyrolyzer produces cleaner, agriculture-ready biochar
Maximum Academic Press
Using reed straw pellets as feedstock, the team found that the system could produce biochar with low toxic risk, strong functional properties, and relatively high energy recovery.
Biochar has attracted growing attention as a carbon-rich material produced by slow pyrolysis in oxygen-limited conditions. It can help stabilize carbon for long periods, reduce carbon dioxide emissions, and improve soils because of its porous structure and nutrient-retention potential. At the same time, biochar production can generate harmful contaminants such as polycyclic aromatic hydrocarbons, making cleanliness an important factor in real-world application. Previous studies have mostly focused on batch slow pyrolysis with external heating, while less is known about continuous, internally heated moving-bed systems, even though these systems may offer better heat transfer, lower costs, and stronger industrial potential.
A study (DOI:10.48130/bchax-0026-0011) published in Biochar X on 13 March 2026 by Hongbin Cong’s team, Key Laboratory of Energy Resource Utilization from Agriculture Residue, Ministry of Agriculture and Rural Affairs, points to a practical route for optimizing industrial biochar production, especially for agricultural uses such as soil improvement, carbon sequestration, and cleaner biomass utilization.
The researchers used reed straw pellets to test an internally heated cigar-type slow pyrolysis system designed as a quasi-moving-bed reactor. In this setup, part of the biomass is burned to provide heat for pyrolysis, while switching the air inlets and gas outlets enables either updraft or downdraft operation. The team examined three pyrolysis temperatures—550, 600, and 650 °C—and also adjusted air distribution rate and cooling mode to compare high and low airflow as well as water cooling and air insulation. The resulting biochars were assessed using a wide range of indicators, including fixed carbon, ash, atomic ratios, specific surface area, pH, cation exchange capacity, electrical conductivity, PAH concentration, toxic equivalence quantity, and energy conversion efficiency. The results showed that some conventional properties remained relatively stable, while others were strongly affected by operating conditions. Fixed carbon content ranged from 38.46% to 44.02%, and the H/C and O/C ratios indicated good long-term carbon stability. Among all indicators, specific surface area was especially sensitive to pyrolysis conditions and increased with temperature. At 650 °C, biochar produced under downdraft, low air distribution, and air insulation showed surface area values 1.46, 2.26, and 3.00 times higher, respectively, than those produced under updraft, high air distribution, and water cooling. By contrast, updraft operation, high air distribution, and water cooling generally improved cation exchange capacity, an important trait for retaining nutrients in soil. Cleanliness was another key finding. PAH concentrations ranged from 0.03 to 0.44 mg/kg, and toxic equivalence values were only 0.39–5.68 µg/kg, both far below the relevant international limits cited by the authors. Still, PAH levels rose significantly under high air distribution and water cooling. At 550 °C, high airflow produced 2.66 times more PAHs than low airflow, while at 650 °C, water cooling generated 6.89 times more PAHs than air insulation. Meanwhile, syngas heating value increased with temperature, and average energy conversion efficiency reached about 75.31%.
Overall, the study shows that internally heated slow pyrolysis can produce biochar that is both functionally useful and environmentally clean, but performance depends strongly on process design. Downdraft operation favored specific surface area, while updraft operation offered some advantages in cation exchange capacity, energy efficiency, and production capacity. The authors conclude that future optimization should balance biochar quality with conversion efficiency to match different agricultural applications and support larger-scale industrial deployment.
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References
DOI
Original Source URL
https://doi.org/10.48130/bchax-0026-0011
Funding information
This work was supported by the National Key Research and Development Project (Grant No. 2024YFD170110401).
About Biochar X
Biochar X is an open access, online-only journal aims to transcend traditional disciplinary boundaries by providing a multidisciplinary platform for the exchange of cutting-edge research in both fundamental and applied aspects of biochar. The journal is dedicated to supporting the global biochar research community by offering an innovative, efficient, and professional outlet for sharing new findings and perspectives. Its core focus lies in the discovery of novel insights and the development of emerging applications in the rapidly growing field of biochar science.
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Influence of cigar-type slow pyrolysis conditions on the physiochemical properties and conversion efficiency of biochar
‘Nature’s algorithm’ found in Chinese money plants
image:
The Chinese money plant, seen here against the backdrop of Cold Spring Harbor, is helping CSHL biologists uncover the mathematical formulas underlying nature itself.
view moreCredit: Nick Wurm/CSHL
Look up at the clouds. What do you see? A sailboat? A seahorse? Your great-aunt Rosemary? As humans, we’re prone to seeing patterns where they don’t actually exist. This behavior is so common there’s a name for it: apophenia. But sometimes, those patterns really do exist. Cold Spring Harbor Laboratory Associate Professor Saket Navlakha specializes in finding them.
Voronoi diagrams are geometric patterns used to divide space into regions. Each region contains a given central point. For example, when dividing a town into school districts (regions), a Voronoi diagram guarantees that all students living within a district are closer to that district’s school (central point) than to any other school. “Voronoi diagrams have been used for centuries in a variety of applications ranging from city planning to network design,” Navlakha says.
Voronoi-like patterns are common in nature—giraffe stripes, for example. However, the keyword there is “like.” The difference between textbook Voronoi patterns and what we see in nature is that the latter usually lacks visible “schools.” Now, Navlakha and former graduate student Cici Zheng have found an exception in Pilea peperomioides, the Chinese money plant.
Chinese money plants are perennials native to China’s Yunnan and Sichuan provinces. You may have received one as a housewarming gift from great-aunt Rosemary. Its round, flat leaves feature prominent pores called hydathodes, surrounded by looping reticulate veins that transport water and nutrients to and from the leaf. By mapping Chinese money plants’ pores and veins, Navlakha and Zheng discovered a naturally occurring Voronoi pattern.
The team then turned to world-renowned scientist Przemysław Prusinkiewicz, who has studied vein patterning for decades. Together, they worked out the “natural algorithm” used to form looping veins around central pores in Chinese money plants’ leaves.
“Just as humans have to solve problems to survive, the same goes for other organisms,” says Zheng, now a postdoc at the Allen Institute. “But unlike humans, plants cannot explicitly measure distances! Instead, they rely on local biological interactions to achieve the same Voronoi solution.”
“We think of these algorithms in nature as an explanation for how organisms will behave and as a way to try to make sense of the world,” Navlakha says. “This example is a nice merger of classical geometry, modern plant biology, and computer science.”
“It’s remarkable how mathematical yet another aspect of plant form and patterning turns out to be,” Prusinkiewicz adds. “For decades, the question of how reticulate veins form has remained open, and finally we have a plausible answer” in Chinese money plants’ Voronoi patterns.
Navlakha and Zheng hope exploring this phenomenon can help tell us how plants work out complex problems in nature. Understanding that may provide a new framework for making sense of the math underlying evolution, development, and life itself.
Left: The round, flat leaf of Pilea Peperomioides, the Chinese money plant. Right: A computer model of a Voronoi diagram traces the leaf’s central hydathode pores and looping reticulate veins.
Credit
Navlakha lab/CSHL
Journal
Nature Communications
Article Title
Reticulate leaf venation in Pilea peperomioides is a Voronoi diagram
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