Sulfomethylation of radiata pine kraft lignin was performed using formaldehyde and sodium sulfite under alkaline conditions to determine its potential as a mineral depressant for the separation molybdenite chalcopyrite by froth flotation. Optimal sulfomethylation reaction were 20% (w/w) Na2SO3 at 130 °C 4.2 h, which resulted in with sulfonate content 2.2 mmol/g. Microflotation assays showed tha...