Reaction mechanisms and products of lead with C6H6 and C6H5OH in incineration of sludge: A theoretical exploration

Abstract

AbstractIn this work, the reactions of Pb and PbO with benzene (C6H6) and phenol (C6H5OH) during sludge incineration were investigated using quantum chemistry methods. Result indicates that Pb reacts with two organics via insertion mechanism to form C6H5PbH, C6H5OPbH, C6H5PbOH, and m‐, o‐, p‐HPbC6H4OH. The energy barriers are modest to overcome, and all products are rather stable with their relative energy from around −130 to −250 kJ/mol; therefore, Pb could be formed as Pb‐organic compounds deposited in bottom ash or fly ash. Moreover, C6H5OPbH is the most feasible products thermodynamically and kinetically. In presence of oxygen, Pb might be oxidized to be PbO firstly, and C6H5PbOH and o‐HOPbC6H4OH were formed when PbO as reactant; the corresponding barriers are high to be 114 and 53 kJ/mol, respectively, indicating these organic‐metal compounds are difficult to generate during incineration of sludge. It implies that O2 free condition is more feasible for Pb to be deposited as compounds in bottom slag or fly ash. Thus, the secondary treatment of bottom slag or fly ash is necessary to reduce the harm of Pb‐contained compounds after sludge incineration.