Valorisation of invasive plant species in the production of polyelectrolytes

•Wood wastes from invasive tree species, Acacia and Ailanthus, were valorised.•New bio-based polyelectrolytes (PELs) were produced by chemical modification methods.•The PELs as flocculants were able to remove turbidity of an olive oil mill effluent.•With 50−100 mg/L PEL dosage, effluent turbidity removals of up to 65 % were achieved.•Results have interest in a circular economy perspective directed to natural materials.