Cadmium uptake by lignocellulosic materials: Effect of lignin content

Two lignocellulosic materials with different lignin contents (18 and 42%wt) and pure lignin (PL) were evaluated for their effectiveness in binding cadmium from dilute solutions in various concentrations. Maximum sorption capacities (X-m), determined from equilibrium isotherms by applying the Langmuir model, indicated that PL (X-m=48.3 mg/g) and the sample with the larger lignin content (X-m=22.2 mg/g) showed a reasonable ability to uptake cadmium. An increasing relationship between X-m and the sample's lignin content was found, considering the tested materials together with others evaluated earlier under identical conditions. Pure lignin attained the highest value. Accordingly, the lignin content of lignocellulosic materials appears as an indicator of their ability to uptake cadmium. It could facilitate their screening for potential use as alternative cadmium sorbents from dilute wastewater. The effects of the sample's dose and the solution pH on cadmium uptake also were investigated.