title: Green stabilization of microscale iron particles using guar gum: bulk rheology, sedimentation rate and enzymatic degradation.
abstract: Guar gum can be used to effectively improve stability and mobility of microscale zerovalent iron particles (MZVI) used in groundwater remediation. Guar gum is a food-grade, environment friendly natural polysaccharide, which is often used as thickening agent in a broad range of food, pharmaceutical and industrial applications. Guar gum solutions are non-Newtonian, shear thinning fluids, characterized by high viscosity in static conditions and low viscosity in dynamic conditions. In particular, the high zero shear viscosity guarantees the MZVI dispersion stability, reducing the sedimentation rate of the particles thus enabling its storage and field operations. In this work, a comprehensive rheological characterization of guar gum-based slurries of MZVI particles is provided. First, we derived a model to link the bulk shear viscosity to the concentration of guar gum and then we applied it for the derivation of a modified Stokes law for the prediction of the sedimentation rate of the iron particles. The influence of the preparation procedure (cold or hot dissolution and high shear processing) on the viscosity and on the stability of the suspensions was then assessed. Finally, the dosage and concentration of enzymes - an environment friendly breaker--were studied for enhancing and controlling the degradation kinetics of the suspensions. The derived empirical relationships can be used for the implementation of an iron slurry flow and transport model and for the design of full scale injection interventions.
authors.affiliation: DIATI - Dipartimento di Ingegneria dell'Ambiente, del Territorio e delle Infrastrutture, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy. Electronic address: francesca.gastone@polito.it.
authors.forename: Francesca
authors.initials: F
authors.lastname: Gastone
authors.affiliation: DIATI - Dipartimento di Ingegneria dell'Ambiente, del Territorio e delle Infrastrutture, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy. Electronic address: tiziana.tosco@polito.it.
authors.forename: Tiziana
authors.initials: T
authors.lastname: Tosco
authors.affiliation: DIATI - Dipartimento di Ingegneria dell'Ambiente, del Territorio e delle Infrastrutture, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy. Electronic address: rajandrea.sethi@polito.it.
authors.forename: Rajandrea
authors.initials: R
authors.lastname: Sethi
mesh_terms: D000327:Adsorption; D004798:Enzymes / Q000737:chemistry*; D005685:Galactans / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008351:Mannans / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D053149:Plant Gums / Q000737:chemistry*; D012212:Rheology
chemical_list: D004798:Enzymes; D005685:Galactans; D008351:Mannans; D053149:Plant Gums; D007501:Iron; C007894:guar gum
keywords: Colloidal stability; Guar gum; Guar gum bulk rheology; Guar gum dissolution; Guar gum enzymatic degradation; Microscale zero-valent iron; Sedimentation tests; Shear thinning fluids