Abstract:
Heavy metals present in industrial wastewater contribute to human and ecosystem health risk when
discharged without proper treatment. Low-cost biosorbents with high metal-binding capacity are
increasingly being utilized for the removal of heavy metals. Inherent physico-chemical properties of
biosorbents significantly influence their adsorption capacity. Studies quantifying the influence exerted by
these properties on adsorption capacity are scarce. This study quantifies the influence and relative
importance of selected physico-chemical properties on the adsorption capacity of three divalent heavy
metals; Cu2þ, Cd2þ and Pb2þ using multivariate analysis. Twenty one biosorbent mixtures were created,
systematically varying their physico-chemical properties using tea factory waste and coconut shell
biochar. Their adsorption capacities were measured using batch sorption studies. The influence of
physico-chemical properties on the adsorption capacity is comparable for all three metal cations.
Regression models were developed to quantify the influence of physico-chemical parameters on the
adsorption capacity based on regression coefficients. All models were found to have high reliability with
R2 values above 0.98. Acidic surface functional groups were found to act as the key property that governs
the adsorption capacity of Pb2þ, Cu2þ and Cd2þ. Carboxylic groups played a major role in the adsorption
of Cu2þ and Pb2þ, while lactonic groups were more important in providing binding sites to Cd2þ. SSA
