Studies on the effect of flocculant adsorption on the dewatering of iron ore tailings

The adsorption characteristics of polyacrylamide polymer on iron ore tailings have been studied to understand the mechanism of adsorption. Adsorptions of both the anionic and non-ionic flocculants were analyzed using Langmuir isotherm and Freundlich isotherm. It was found that in comparison to the Langmuir model the Freundlich model was a better fit to the adsorption data according to the minimum variance criterion. It was established with the support of the Langmuir model that the adsorption of anionic and non-ionic flocculants is facilitated by hydrogen bonding. The zeta potential affects the settling rate and in this case the isoelectric point of the tailings which is basically a mixture of various oxides was measured to be 4.66. The settling rate was found to increase when the pH decreased from 10 to 5. The settling rate increased with increasing flocculant dosage up to a maximum value at 80 g polymer/t solid corresponding to the maximum adsorption of polymer. However, at higher pH the clarity of supernatant liquid was very poor and flocculation was not effective for ultrafine particles at that pH.

► Adsorption of polyacrylamide flocculants onto the iron ore tailings is established.
► Effects of pH and flocculant doses on zeta potential of the tailings were studied.
► Adsorption data was validated with Langmuir and Freundlich isotherm models.
► Flocculation and settling studies were carried out to optimize dewatering conditions.
► The investigation outcomes are directly applicable to dewatering practice in mineral industries.