An Evaluation of Quartz as a Component of Respirable Coal Dust

The rising cases of coal worker’s pneumoconiosis since the early 2000s have driven research into respirable coal dust. Prolonged quartz dust exposure is deemed to be the primary cause of the resurgence in pneumoconiosis. This study examines how quartz present in coals of various ranks produces hydroxyl radicals (•OH), a reactive oxygen species linked to particle toxicity. This study evaluates the ability of safe chemical additives to reduce •OH production of the coal-quartz samples at various pH levels. Promising chemicals were investigated in different solutions, including tap and process waters and simulated lung fluid (SLF). We combined insights from electrokinetic measurements, infrared and X-ray photoelectron spectroscopies, and ab initio atomistic simulations to study the quartz particle surfaces. The study also explored how surface aging impacts quartz •OH production. The results reveal that •OH generation of the quartz varies and is enhanced by iron contamination, as also confirmed by ab initio simulations. Iron also enhances hydroxamic acid adsorption, leading to stronger interaction of the reagent on the quartz surface. Fresh quartz surfaces are particularly prone to generating more •OH in alkaline conditions. Carboxymethyl cellulose was notably effective in inhibiting quartz •OH by about 91% at pH 7 in deionized water. The production of •OH was minimal in SLF compared to other tested solutions. The negative charge on quartz surface in various aqueous solutions was found to impact •OH generation. Quartz surface aging results in a gradual decrease in •OH generation due to the decay of surface siloxyl radicals.