at initial pH ranging from 2.0 to 6.0, the equilibrium pH values are higher than the initial values. When initial pH is 7.0 and 8.0, the corresponding equilibrium pH values are slightly decreased. The Pb adsorption capacity increases sharply from 19.7 to 46.4 mg g−1 with the pH elevation from 2.0 to 5.0, and maintains almost constant from pH 6.0 to 8.0.
This trend is similar to that of Pb adsorption by other modified biomass [38] and can be interpreted as follows. Under acidic conditions,