Carbamoylethylated Wood Pulp as a New Sorbent for Removal of Hg (II) from Contaminated Water: Isotherm and Kinetic Studies

Abstract

Mercury is a persistent, heavy metal present in watercourses, and this paper presents the synthesis of a new, low-cost sorbent, based on wood pulp, for the targeted removal of Hg (II) from aqueous solutions. Carbamoylethylated wood pulp sorbents were obtained from the reaction of wood pulp with acrylamide, in basic media, to produce a suite of materials with varying nitrogen concentration (0.251.51%). Batch sorption techniques were used to determine the sorption capacity of each sorbent for Hg (II), as a function of pH, contact time, as well as sorbate and sorbent concentrations. The samples were evaluated for bulk and surface chemistry (nitrogen concentration and FTIR) as well as surface morphology and textural properties (SEM and surface area measurements). Sorption analysis via Langmuir, Freundlich and Temkin models, showed that the data were best represented by the Temkin isotherm model suggesting influence from surface heterogeneity in the adsorption process. Langmuir analysis provides an indication of the maximum sorption uptake at 787.6 mg g−1, while Freundlich analysis shows the sorption process to be favourable but with some slight suppression at low concentrations. The results indicate the importance of nitrogen concentration and corresponding sorption capacity in Hg (II) sorption kinetics and are consistent with the recovery rates observed. Sorption tests demonstrate that these sorbents have remarkable potential, which is validated through 39% removal of Hg (II) from aqueous solution, and modelling of the kinetic data showed that the system closely flows a pseudo-second-order kinetic model.