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. 2019 Sep 17;12:222. doi: 10.1186/s13068-019-1568-7

Table 1.

The content of ash, surface charge, acid buffering capacity, and cation exchange capacity of the presoaked and raw WWS

Sample	Soaking reagent	Concentration (mmol/L)	Ash (%)	SC^a (mv)	CEC^b (cmol/kg)	ABC^c (mmol/pH-kg)
Raw WWS	No soaking	–	30.5 ± 0.8	− 25.9 ± 1.1	140.2 ± 1.8	226.3 ± 1.2
	H₂O	–	25.2 ± 1.5	− 24.1 ± 1.3	133.7 ± 2.5	201.4 ± 3.7
	H⁺	30	26.8 ± 1.1	− 22.2 ± 0.3	116.3 ± 1.8	146.7 ± 3.2
	K⁺	30	24.9 ± 1.3	− 23.5 ± 0.5	122.6 ± 2.5	168.9 ± 3.5
	Na⁺	30	27.5 ± 0.7	− 24.7 ± 0.2	118.9 ± 1.4	150.7 ± 2.6
	Ca²⁺	30	23.3 ± 0.5	− 16.3 ± 0.4	135.6 ± 4.6	179.9 ± 2.1
	Mg²⁺	30	24.8 ± 1.2	− 18.5 ± 1.3	109.2 ± 0.9	147.3 ± 4.1
	Zn²⁺	30	26.3 ± 0.4	− 17.6 ± 2.1	96.5 ± 1.3	140.6 ± 1.5
	Fe²⁺	30	25.7 ± 0.2	− 10.5 ± 0.3	80.8 ± 1.1	94.3 ± 2.2
	Fe²⁺	10	23.1 ± 0.1	− 14.7 ± 0.5	97.4 ± 2.8	133.9 ± 1.6
		20	26.3 ± 0.3	− 13.2 ± 0.1	90.5 ± 3.2	119.3 ± 2.3
		30	25.8 ± 0.7	− 11.1 ± 0.0	81.6 ± 1.4	95.6 ± 1.9
		60	24.5 ± 1.1	− 10.8 ± 0.8	74.3 ± 4.2	89.5 ± 2.6
		120	24.3 ± 0.3	− 4.7 ± 0.2	72.4 ± 1.7	79.3 ± 1.0

^aSurface charge

^bCation exchange capacity

^cAcid buffering capacity