Mechanisms involved in sorption of metals by chemically treated waste biomass from irrigation pond

Several analytical techniques (FTIR, SEM–EDS and acid–base titration) have been used to characterize an irrigation pond biomass after chemical modification with different pretreatment agents (NaHCO₃, Na₂CO₃ and NaOH, with and without a subsequent washing treatment) in order to explain the observed increase in different metals sorption uptake (Cd²⁺, Cu²⁺, Ni²⁺, Pb²⁺ and Zn²⁺). It was found that chemical pretreatments favoured anchoring of Na⁺ on the active sites of the biomass and in turn metal uptake by ion exchange. In addition, higher cell wall porosity was observed, which increased the availability of new innermost active centres in the biomass. The active sites were loaded with Ca²⁺, which was also involved in the metal ion exchange process.