Anionic polyacrylamide efficiency in goethite removal from aqueous solutions: goethite suspension destabilization by PAM

The main aim of the study was to investigate the anionic polyacrylamide (PAM) efficiency as a flocculant relative to goethite particles. This mineral is a toxic waste produced during hydrometallurgical processes and, as a result, poses a threat to the environment. In the experiments, the following analytical methods were applied: potentiometric titration, zeta potential and adsorption amount measurements, nitrogen adsorption/desorption isotherms, Fourier transform infrared spectroscopy, differential centrifugal sedimentation, UV/Vis spectrophotometry. The result analysis showed that polyacrylamide adsorbs on the goethite surface; however, its adsorption amount depends on the pH value. Due to the adsorbent–adsorbate electrostatic repulsion, the smallest number of macromolecules adsorbs at pH 9. The PAM adsorption affects the goethite surface charge and zeta potential values. It makes these parameters more negative. What is more regardless of pH value, the polymer addition contributes to clear aggregation of solid particles (suspension destabilization). Thus, PAM can be considered as a potential flocculant improving the goethite removal from aqueous wastes.