Ammonium hydrogen phosphate nh4 2hpo4

Chitosan (CTs) was acquired from Aldrich Chemical Company, Inc. (Milwaukee, WI, USA) and Hydroxyapatite (HAp) was produced according to a previously published technique [17 (link)].
Ammonium hydrogen phosphate (NH₄)₂HPO₄ (99%), calcium nitrate Ca(NO₃)₂·4H₂O (99%), lysine, Acetic acid (99%), and cadmium chloride (CaCl₂) were all purchased from Sigma Aldrich (Waltham, MA, USA) and utilized precisely as received, with no additional purification. Both runs utilized distilled water of high quality.
A Cd²⁺ and Zn²⁺ stock solution with a concentration of 1200 ppm (S0) was prepared.
Then, a series of diluted Cd²⁺ and Zn²⁺ solutions with concentrations of 300, 210, 170, 120, 100, 80, and 40 ppm were produced.

The synthesis of Ca_10−xMg_x(PO₄) ₆(OH)₂, was conducted using calcium nitrate tetrahydrate, Ca(NO₃)₂∙4H₂O (Sigma Aldrich, St. Louis, MO, USA, ≥99.0%), ammonium hydrogen phosphate, (NH₄)₂HPO₄ (Sigma Aldrich, St. Louis, MO, USA, ≥99.0%) and magnesium nitrate hexahydrate, Mg(NO₃)₂·6H₂O (Alpha Aesar, Germany, 99.97% purity), ammonium hydroxide, NH₄OH [Sigma Aldrich, St. Louis, MO, USA, 25% NH₃ in H₂O (T)], ethanol absolute, C₂H₆O (Sigma-Aldrich, Sigma Aldrich, St. Louis, MO, USA ≥99.8% purity) and double distilled water.

In order to obtain magnesium doped hydroxyapatite (Ca_10−xMg_x(PO₄)₆(OH)₂; x_Mg = 0.1; (Ca + Mg)/p = 1.67) in chitosan matrix, calcium nitrate tetrahydrate (Ca(NO₃)₂∙4H₂O, Sigma Aldrich, St. Louis, MO, USA, ≥99.0%), magnesium nitrate hexahydrate (Mg(NO₃)₂·6H₂O, Alpha Aesar, Kandel, Germany, 99.97% purity), ammonium hydrogen phosphate ((NH₄)₂HPO₄, Sigma Aldrich, St. Louis, MO, USA, ≥99.0%) ammonium hydroxide (NH₄OH, Sigma Aldrich, St. Louis, MO, USA, 25% NH₃ in H₂O (T)), chitosan (Sigma Aldrich, St. Louis, MO, USA) and double distilled water were used as precursors without further purification.