Synthesis of Al-substituted 11 Å tobermorite from newsprint recycling residue: a feasibility study

Newsprint recycling is responsible for significant volumes of secondary waste material for which further reprocessing and market development would be beneficial. In response to this problem, a layer lattice, ion exchange material, Al-substituted 11 Angstrom tobermorite, has been synthesised from newsprint recycling residue comprising gehlenite (Ca2Al2SiO7) akermanite (Ca2MgSi2O7), beta-dicalcium silicate (Ca2SiO4) and anorthite (CaAl2Si2O8) under hydrothermal conditions at 100 degreesC in the presence of NaOH. The hydrogamet phase, katoite (Ca3Al2SiO12H8), was also formed. Similar treatment regimes in the presence of LiOH and KOH did not yield significant quantities of Al-substituted 11 Angstrom tobermorite. A batch sorption study confirmed that the Al-substituted 11 Angstrom tobermorite-bearing product was effective in the exclusion of Cd2+, Pb2+ and Zn2+ from acidified aqueous media. The potential to enhance the yield of Al-substituted 11 Angstrom tobermorite relative to that of katoite and thus optimise the ion exchange efficiency of the product is discussed with respect to its application to heavy metal-contaminated wastewater treatment.