Ecofriendly Refuse Biopolymers as Auxiliaries for Washing Soil Contaminated by Heavy Metals: a Case Study

Urban refuse provide a range of polymeric biosurfactants (BPS) with different chemical nature depending on the sourcing biowaste (BW). Six different BPS were isolated from BW sourced from a waste management plant located in Pinerolo (TO). These products had molecular weight in the 5-500 kD range and were characterized by the presence of aliphatic C chains substituted by aromatic moieties and COOH, CON, C=O, PhOH, O-R, OAr, OCO, OMe, and NRR’(R and R’ = H and/or or alkyl) functioal groups. Surface tension studies allowed to establish that BPS behave as typical small molecule surfactants and/or polyelectrolytes depending on concentration. The above BPS were used in aqueous solution to wash soil sampled from a heavily contaminated industrial site in North Italy, containing organic and metal pollutants. They had high affinity mostly for Cu and Zn, and less for Ni and Pb. Experimental trials were performed to assess the soil-washing solution equilibrium contact time. Soil column washing trial at equilibrium contact time were performed to optime the experimental conditions for efficient removal of the above metals form the soil. A new process was developed comprising washing the polluted soil with the above aqueous BPS solution, solution, and treating the recovered solutions by chemical and/or chemical-physical means to separate the pollutant concentrate and obtain clean water for further uses. The same process was shown to have intriguing potential for treating also industrial water effluents and/or ground water.