Synergistic effects of N-Containing functional groups and calcium binding sites on arsenic adsorption by Ca-N Co-doped microalgae-derived biochar

초록

Spirulina platensis (SP), a nitrogen-rich microalga, was used to synthesize Ca-N co-doped biochar through direct calcium doping and pyrolysis at elevated temperatures. This approach aimed to enhance the physicochemical properties and adsorption performance of biochar for arsenic (As) remediation. Pyrolysis temperature profoundly influenced biochar composition, promoting advanced carbonization, graphitization, and crystallinity, while reducing volatile elements such as nitrogen, hydrogen, and sulfur. Calcium doping facilitated the formation of CaCO3 and CaO, contributing to microporous and mesoporous structures with increased surface area and improved structural stability. Surface analyses confirmed the generation of Ca-N-C composite structures, which shifted surface charges positively and enhanced As adsorption affinity. Batch adsorption experiments revealed that the CaSP900 biochar exhibited superior adsorption capacity and selectivity for As(V) over As(III) across a wide pH range and in the presence of competing ions. Mechanistic insights indicated that As removal involves electrostatic attraction, surface complexation, and Ca-mediated precipitation. Additionally, the biochar demonstrated excellent regeneration potential without significant loss in adsorption efficiency after multiple cycles. These findings highlight the potential of Ca-N co-doped biochar as a sustainable and effective adsorbent for arsenic-contaminated water treatment.

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