Effect of Carbon Dioxide Gas Flow Rate on Production of PCC from Carbide Lime Waste

Abstract

Carbide lime or lime sludge is a by-product of acetylene manufacturing through a hydrolysis of calcium carbide (CaCl₂). In Malaysia, carbide lime is classified as a scheduled waste under Environmental Quality Act: EQA 1974 (SW 427). This industrial waste is frequently rich in calcium hydroxide (Ca(OH)₂), rendering it a substitute potential precursor for producing marketable precipitated calcium carbonate (PCC). In addition to the abundant carbide lime waste, the acetylene production has also increased carbon dioxide (CO₂) gas emission that traps heat in the atmosphere. This phenomenon has become a crucial environmental concern as the rise of CO₂ gas emission leads to global warming. In order to overcome this environmental issue, the pair of carbide lime waste and CO₂ gas were utilized as primary precursors in producing commercial-grade PCC. The precipitation process was achieved via feasible carbonation approach promoted using natural sucrose solution in extracting Ca²⁺ ions from the carbide lime waste. In investigating the effect of CO₂ supply on the PCC formation, CO₂ gas flow rate was varied i.e. 200, 400, 600, 800 and 1000 ml/min. Increasing the CO₂ flow rate resulted in significant time reduction (from 33 min at 200 ml/min to only 9 min at 1000 ml/min) and particle refinement (from 5.28 µm at 200 ml/min to 1.16 µm at 1000 ml/min). Production of PCC with purity 96–98% suggested that the carbide lime waste was successfully transformed into marketable PCC, thus may help in preserving environmental sustainability.