Use of residual diatomaceous earth as a silica source in geopolymer production

Abstract

The use of binders as an alternative to Portland cement has gained importance in recent years. Among them, geopolymeric binders, developed by the reaction between an aluminosilicate precursor and a high alkalinity solution, have become one of the most promising alternatives. The activating solution generally comprises waterglass and sodium hydroxide. Since waterglass is the most expensive material and has a high environmental impact, using alternative silica sources will lead to more sustainable binders. Previous studies have successfully used rice husk ash (RHA) as a silica source. This research aims to assess the possibility of using diatomaceous earth (or diatomite) as an alternative silica source, like the previous studies with RHA. Diatomite is a sedimentary rock with a high amorphous silica content formed by fossilized diatom remains. In this work, the geopolymer was obtained using a fluid cracking catalyst residue as the precursor and six different activating solution types prepared with commercial products, residual diatomite (from beer and wine industries) and RHA. The results open a new possible route for the reuse and recovery of diatomaceous earth residue, although the compressive strength results of the mortars were slightly lower than those for mortars prepared with RHA or commercial reagents.

Reuse of Industrial and Agricultural Waste in the Fabrication of Geopolymeric Binders: Mechanical and Microstructural Behavior

“…To dissolve the silica from DE, the authors mixed KOH, deionized water, and DE in a closed container, and the mixture was stirred overnight. Finally, Font et al [ 23 ] employed dried diatomaceous earth that derived from the beer filtration process (DB) and used FCC as precursor. They dissolved the silica of the DB with NaOH in a thermal bottle for 24 h.…”

Design and properties of 100% waste-based ternary alkali-activated mortars: Blast furnace slag, olive-stone biomass ash and rice husk ash

“…In such case, the alkaline solution is composed of NaOH/KOH solution and an amorphous silica source. The main silica sources are rice husk ash (RHA), diatomaceous earth residues (DE), glass waste, sugar cane straw ash (SCSA) and silica fume (SF), among others (Font et al, 2018;Payá et al, 2017).…”

Eco-efficient alkaline activated binders for manufacturing blocks and pedestrian pavers with low carbon footprint: Mechanical properties and LCA assessment

“…Considering that the manufacture of sodium silicate is energy-intensive and generates CO 2 emissions, in the last years, the studies have focused on the search for alternative activators. Industrial byproducts and wastes have been studied, such as rice husk ash (RHA) (9), waste glass (10), diatomaceous earth (11), silica fume (12), among others.…”