Development of a sorbent carrier based on apatite-nepheline ores and their beneficiation wastes

Sorption is among the most effective and affordable methods for soil remediation. Although numerous sorbents exist, only a small fraction are synthesized from industrial waste materials. Composite inorganic sorbents based on phosphates represent a promising category in this regard. This study focuses on producing porous phosphate-based sorbent carriers for cleaning oil-contaminated sites, using glassy phosphate fertilizers (GPF) derived from apatite-nepheline ores and beneficiation wastes. The manufacturing process resembles foam glass production but differs in the selection of foaming agents, additives, temperature regimes, and furnace residence time. The foaming agent must release gaseous products upon thermal decomposition within the softening temperature range of the glass mass. Over 13 foaming agents were evaluated based on this criterion, leading to the selection of three candidates: nitroammophoska (ammonium nitrate phosphate fertilizer or NAF), calcium nitrate, and chalk. NAF was chosen for further experiments. Phosphate carriers made from GPF combined with NAF demonstrate a contaminant removal efficiency of 93 % at high pollution levels. Activation of these carriers can boost removal efficiency to 99 %. Moreover, the biodegradable nature of the carrier material eliminates the need for post-treatment waste collection. The selection of specific carriers for remediating various contaminated surfaces was guided by their morphological properties and mechanical abrasion resistance. This assumption is further supported by the evaluation of activated carriers under experimental conditions, which included measuring the rates of decomposition and the levels of oxidation products before and after treatment, analyzing the kinetics of oil absorption, and examining surface morphology using scanning electron microscopy.