Production of chelated micronutrient fertilizers from metal-containing wastewaters using biodegradable chelating agents

Abstract

This thesis investigates the application of biodegradable chelating agents for the removal and recovery of essential micronutrients such as iron (Fe), copper (Cu), zinc (Zn), and manganese (Mn) from wastewater, with a focus on their potential use in sustainable fertilizer production. A comprehensive study of fifteen chelators, including ethylenediaminedisuccinic acid (EDDS), L-glutamic acid N, N-diacetic acid (GLDA), methylglycinediacetic acid (MGDA), and N-(1,2-dicarboxyethylene)-D, L-asparagine acid (IDS), was conducted to evaluate their effectiveness in forming stable and bioavailable metal complexes across a wide pH range, which is critical for agricultural applications.

The research demonstrates that the direct synthesis method effectively integrates these chelators with metal ions, resulting in micronutrient-rich fertilizers that enhance plant nutrient availability. This approach ensures that micronutrients are retained as essential components rather than being treated as impurities. While traditional chelating agents like Ethylenediaminetetraacetic acid (EDTA) and Nitrilotriacetic acid (NTA) have been well-documented as regeneration agents, EDDS and GLDA have emerged as promising biodegradable alternatives.

In wastewater treatment, EDDS, GLDA, MGDA, and IDS were found to be highly effective in chelating and recovering essential micronutrients from waste streams, significantly reducing environmental contamination. The study highlights EDDS's capability in extracting Zn and Cu from sewage sludge and GLDA's proficiency in remediating cadmium (Cd), nickel (Ni), and Cu. MGDA's role in minimizing secondary pollution and IDS's high extraction efficiencies in battery industry sludge further demonstrate the potential of these agents in diverse pH conditions.

The findings underscore the importance of continued research to optimize these biodegradable chelating agents for wider applications in nutrient recovery and sustainable fertilizer production, with the aim of supporting agricultural productivity while minimizing environmental impact.