Pearson’s linear correlation coefficients between biochar characteristics and the q_max values in the Langmuir model.

	Cb	N	O	H	O/C	H/C	(O + N)/C	S BET c	V tot	Pore width
q max	0.752	−0.867	−0.042	−0.405	−0.768	−0.847	−0.871	0.975a	0.806	0.102

^aCorrelation is significant at the 0.05 level (2-tailed).

^bThe content of C, N, O and H elements in the biochar.

^cThe S_BET and V_tot represent the Brunauer–Emmett–Teller surface area and total pore volume respectively.