Synthesis of Al-substituted 11 إ 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 Å tobermorite, has been synthesised from newsprint recycling residue comprising gehlenite (Ca2Al2SiO7), akermanite (Ca2MgSi2O7), β-dicalcium silicate (Ca2SiO4) and anorthite (CaAl2Si2O8) under hydrothermal conditions at 100 °C in the presence of NaOH. The hydrogarnet 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 Å tobermorite. A batch sorption study confirmed that the Al-substituted 11 Å 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 Å 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.