Environmental application of dicarboxylated hairy cellulose crosslinked with calcium for removal and confining of Pb(ii)†

Abstract

Cellulose can be oxidised with periodate to obtain hairy cellulose, which, thanks to the aldehyde groups, facilitates chemical modification with different functional groups, such as carboxylates, which enhance interaction with various types of analytes. The dicarboxylated product is soluble in water, and in some cases, this is a disadvantage as it can complicate phase separation and quantification of the analyte of interest. Crosslinking with calcium produces an insoluble solid (DCCa) that can be used as a sorbent; therefore, in this work DCCa application in the removal and confinement of Pb(II) was evaluated. The removal process was carried out in a column, optimised with the assistance of a Box–Behnken design and found as optimal conditions: pH 4.3, 15 mg of sorbent and 80 minutes of contact time; with these conditions, it was possible to achieve more than 90% removal of the ion in solution. The process was analysed with a breakthrough curve, and the Yan model showed the best fit to the data; from this, a sorbent capacity of 615.21 mg_Pb g⁻¹ was estimated. Interference from other metallic ions was also evaluated, and there was no significant change in removal percentage. Thus, the sorbent removed more than 80% of Pb(II) from industrial synthetic wastewater. Finally, the sorbent capacity as a confining material for lead was evaluated with different lixiviation and sequential extraction techniques; these analyses showed that it is possible to contain more than 98% of the ion in mild conditions (0.11 mol L⁻¹ acetic acid and 0.5 mol L⁻¹ hydroxylamonium chloride), which makes it a competitive material for the removal and confinement of Pb(II).