Sustainable production of nanolime using plant extracts by fermentation: A traditional approach towards conservation of heritage structures

Abstract

Nanolimes have emerged as efficient consolidants for the conservation of historic and heritage structures. This research investigates an effective, economical, and sustainable way of synthesizing nanolimes using hydraulic lime and natural plant extracts. The lime is fermented with aqueous organic extract for 14 days to produce nanolimes. The fermented compounds in liquid phases and the organic extract were identified using high-performance liquid chromatography (HPLC) and gas chromatography with mass spectrometry (GC-MS). Alcohols, which are substantial fermentation byproducts, were found to aid the nanoscale dispersion of portlandite particles. The narrow size distribution and mean particle size of 130–290 nm in seven-day fermented samples were able to penetrate deeper into treated surface strata for better conservation of structures. The presence of portlandite and calcite nanoparticles observed by X-ray diffraction in nanolime assisted to fill the pores that are too big for nano-portlandite alone and intensifies its ability to hold the grains of the treated surface. The biomineralization process resulted in the development of carbonate compounds ranging in size from 0.4 to 50 nm, thus rendering nanolime as more effective and facilitating the filling of nanopores smaller than 100 nm, which eventually signifies the durability of structure. Ultimately, this research emphasizes importance of nanotechnology in resurrecting tangible heritage.