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.