Potassium nitrate

Sodium hypochlorite (NaClO, 14%), sodium hydrogen phosphate (NaH₂PO₄), sodium chloride (NaCl), calcium chloride dihydrate (CaCl₂∙2H₂O), magnesium sulfate heptahydrate (MgSO₄∙7H₂O), sodium hydrogen carbonate (NaHCO₃), potassium nitrate (KNO₃), sodium nitrate (NaNO₃), calcium carbonate (CaCO₃), magnesium chloride hexahydrate (MgCl₂∙6H₂O), potassium sulfate (K₂SO₄), sodium sulfate (Na₂SO₄), calcium sulfate dihydrate (CaSO₄∙2H₂O), boric acid (H₃BO₃, 0.5%), hydrogen peroxide (H₂O₂, 30%), and chloride acid (HCl, 0.1 M) were purchased from Scharlab S.L., Barcelona, Spain. The ultrapure water (Milli-Q) used in the experiments was obtained from Millipore, Molsheim, France, equipment (conductivity less than 0.055 µS cm⁻¹).
Polyvinyl chloride (PVC, Mw 112,000 g mol⁻¹) was supplied by ATOCHEM, Madrid, Spain. Tetrahydrofuran (THF) was purchased from Scharlab S.L. Amberlite^® IRA-402 (Cl⁻ form, total exchange capacity ≥ 1.0 mol L⁻¹) was supplied by Merck Life Science, Darmstadt, Germany, S.L.U.

All reagents were analytical-reagent grade unless otherwise stated. Potassium nitrate (99%) and sodium chloride (99.5%) were obtained from Scharlau (Barcelona, Spain). Kerosene and ammonia (30%) were obtained from Panreac (Barcelona, Spain). Sodium thiosulfate (100%) was purchased from Merck (Darmstadt, Germany). Tri-isobutylphosphine sulfide (TIBPS) was provided by Cytec Industries Inc (Saddle Brook, NJ, USA), and humic acids were obtained from Aldrich (Steinheim, Germany). Aqueous solutions of silver were prepared from a 1000 mg L⁻¹ standard solution obtained from Merck (Darmstadt, Germany). Deionized water of resistivity lower than 18.2 MΩ cm was obtained by a Millipore Quantum Ultrapure water supplier (Millipore, Bedford, Ma, USA). Acetylene for atomic spectrometry was obtained from Air Liquide (Madrid, Spain).

Bleached eucalyptus kraft
pulp, unrefined (15 °SR), was provided by Ence (Navia, Spain).
2,2,6,6-Tetramethylpiperidine-1-oxy radical (TEMPO), NaBr, NaOH, NaClO
(15%), copper(II) ethylenediamine, and DTZ (≥98%) were purchased
from Sigma-Aldrich (Schnelldorf, Germany). Glacial acetic acid was
purchased from Scharlab (Sentmenat, Barcelona, Spain). All organic
solvents (reagent grade) were received from Thermo Fisher Scientific
(Loughborough, U.K.). Preliminary results indicated that amylene-stabilized
chloroform is preferred over ethanol-stabilized chloroform.
Distilled water was used for nanocellulose production, but metal
salts were dissolved in Milli-Q water. These metal salts were lead(II)
nitrate, lead(II) chloride, cadmium(II) nitrate, cadmium(II) chloride,
copper(II) chloride, nickel(II) chloride, chromium(III) chloride,
chromium(III) nitrate, and magnesium chloride from Panreac Applichem
(Castellar del Vallès, Barcelona, Spain); potassium nitrate,
iron(III) chloride, and manganese(II) chloride from Scharlab; and
mercury(II) nitrate 1-hydrate, mercury(II) chloride, silver nitrate,
and zinc chloride from Sigma-Aldrich.