Multi-method approach for the study of sludge effects on heavy metal-soil interactions

A multi-method approach has been developed to study interactions between he avy metals and solid matrices and to obtain the relative data In particular , adsorption isotherms and breakthrough curves were used to study the inter actions between Cu(II) ions and soil and to study the effects that the comp ounds present in urban sludges, settled on soils, have on heavy metal-soil equilibria. Electrophoresis in a stabilised medium was used to study direct ly on the soil column the buffer capacity of soil metal mobility in soil th e nature of the chemical forms of the metals, the metal amount that the soi l was able to retain and the changes that the compounds present in the slud ge had induced on the above reported physicochemical properties. The result s obtained with batch studies and breakthrough curves underline the increas e of the number of son sites which can bind heavy metals when wastewater sl udge is adsorbed on soil; the electrophoretic method gives the possibility to prove that the metal retained by soil in contact with sludge, is present in a non mobile form.