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Four distinct biochars were employed to remove three typical pollutants, meanwhile, path analysis, a multi-statistical regression method, was performed to elucidate the dominant factors of biochar adsorption. This work can provide a new insight to prepare a targeted biochar as adsorbents.

In this work, a modification method of H3PO4plus H2O2(PHP) was introduced to targetedly form abundant oxygenated functional groups (OFGs) on biochar, and methylene blue (MB) was employed as a model pollutant for adsorption to reflect the modification performance. Results indicated that parent biochars, especially derived from lower temperatures, substantially underwent oxidative modification by PHP, and OFGs were targetedly produced. Correspondingly, approximately 21.5-fold MB adsorption capacity was achieved by PHP-modified biochar comparing with its parent biochar. To evaluate the compatibility of PHP-modification, coefficient of variation (CV) based on MB adsorption capacity by the biochar from various precursors was calculated, in which the CVof PHP-modified biochars was 0.0038 comparing to 0.64 of the corresponding parent biochars. These results suggested that the PHP method displayed the excellent feedstock compatibility on biochar modification. The maximum MB adsorption capacity was 454.1 mg/g when the H3PO4and H2O2fraction in PHP were 65.2% and 7.0%; the modification was further intensified by promoting temperature and duration. Besides, average 94.5% H3PO4was recovered after 10-batch modification, implying 1.0 kg H3PO4(85%) in PHP can maximally modify 2.37 kg biochar. Overall, this work offered a novel method to tailor biochar towards OFGs-rich surface for efficient adsorption.