Activated and enriched “designer” biochar as sorbent in remediation of PFAS and metal contaminated soils

Soil contamination has become a major environmental problem of global concern, and there is a need for effective remediation methods to counteract this problem. Immobilisation of contaminants in soil using the carbonaceous material biochar as a sorbent can make an important difference in the future, as it is both a sustainable and cost-effective remediation alternative. However, there is still much unknown about biochar’s sorption capacity for various contaminants and this thesis therefore aims to contribute knowledge to this existing knowledge gap. In order to investigate the sorption of a group of organic pollutants called per- and polyfluorinated alkyl substances (PFAS) and metals/metalloids (lead, copper, and antimony) to biochar in contaminated soil, one-step batch leaching tests were conducted, with increasing dose of biochar added. Previous research has shown that biochar has potential for improvement as a sorbent material and therefore two types of "designer" biochars were investigated in this thesis. In the PFAS contaminated soil, different activated biochars were tested and in the metal contaminated soil, biochars enriched with zero-valued iron and sulfur were tested. In soil with low organic matter (OM) content, the addition of activated biochar gave an almost 100% reduction in PFAS leaching already at a dose of 0.5%. Sorption of PFAS in soil with high OM content required a dose of 5% to observe a clear reduction in PFAS leaching. Fully activated biochar gave the most effective PFAS sorption in both soil types. In metal/metalloid contaminated soil, biochar enriched with zero-valued iron had the best ability to sorb both lead, copper and antimony. A dose of 10% was required to get a clear effect in soil with both high and low OM content. So far, the research on such types of "designer" biochar is scarce. The present work provides promising prospects for biochar as an effective sorbent material in soil remediation. Further research on activated biochar and iron-enriched biochar is needed to gain a better understanding of the sorption capacity and the underlying sorption mechanisms