Containment and Dewatering of Heavy Metal Contaminated Slurries Using Reactive Minerals and Cellulose Materials in Geotextile Tubes

The aim of this study is to investigate effective and sustainable measures to contain heavy metal contaminated sediments inside a geotextile tube during the dewatering process. A series of batch adsorption and pressure filtration tests (PFT) evaluated the efficacy of cellulosic materials (kraft pulp, jute fibers, and peanut hulls) on adsorption of selected heavy metals (Pb²+, Cu²+, Zn²+, and Cd²+) and the dewatering performance inside a geotextile tube. The batch adsorption tests conducted on two soils, sandy and silty in composition (Tully sands and Tully fines) with metal ions show that they have a very high affinity towards Pb and Cu compared to Cd and Zn. The maximum adsorption capacity as calculated from the batch adsorption of Tully sand to Pb and Cu are 33.12 and 6.54 mg/g, respectively. The Tully fines had even higher adsorption capacities of 57.3 mg/g Pb and 9.48 mg/g Cu. The concentration of filtrate collected from PFT, measured using ICP OES (inductively coupled plasma optical emission spectrometry), also shows that Tully fines were able to adsorb 99% Pb and Cu, 88% Cd, and 83% Zn. Meanwhile, Tully sand adsorbed 96% Pb, 90% Cu, 81% Cd, and 76% Zn. Although significant adsorption was accomplished by both soils rich in reactive minerals illite, chlorite, and calcite, the addition of cellulosic materials provided additional benefits in dewatering. Among three cellulosic materials, the addition of jute fibers significantly reduced the water content of the Tully sand filter cake by 44%. Since kraft pulp has a tendency to adsorb water and swell, water content as high as 40% was measured. The water content did not change significantly with the use of peanut hulls. All the cellulosic materials were successful in improving the overall turbidity of the filtrate. A drop in turbidity of more than 60-80% was observed with the addition of jute fibers.