Development of low heavy metal − Linz-Donawitz slag for safe spinach cultivation

Linz-Donawitz Slag is regarded as a soil conditioner and can be exploited for its mineral and nutritional value in agriculture, however, it is necessary to check the Potentially Toxic Elements (PTEs) which could impact the soil rapidly and crop production adversely. Environmental hazards associated with mounting piles of Linz-Donawitz slag emanating from the steel producing industry and its sustainable management are a major challenge. A research study was carried out using different chemical chelating agents to achieve reduction in PTEs' concentration in Linz-Donawitz slag and to study the effect of transfer of PTEs’ from the treated and untreated LD Slag applied to the spinach. Optimization was done using response surface methodology, and the highest extraction efficiency for Cadmium (Cd) and Lead (Pb) removal was observed using a concentration of 10 mM, liquid-to-solid ratio of 5:1, and shaking time of 60 min to obtain Low heavy metal Linz-Donawitz slag (Low HM-LD Slag). The highest chelation was observed while using the chelating agent Ethylene diamine-N, N'-Di succinic acid (EDDS) followed by Ethylene diamine tetra acetic acid (EDTA) then Diethylene triamine penta acetate (DTPA), and the least extraction was observed using the Citric acid (CA). The Low HM-LD Slag so obtained was assessed for its response on Spinach under the varied level of Recommended Dosage of Fertilizer (RDF) under field soil in pot culture. A significant difference in the growth of spinach was observed between 100% RDF treated Low HM-LD Slag and 50% RDF treated Low HM-LD Slag derived using different chelating agents The PTE analysis of soil and plant showed an undetectable level of Cd, Pb in both the shoot and root samples Under Low HM-LD Slag treatments @ 100% and 50% RDF condition. The present work advocates the use of chemical chelators reducing PTEs' load in Linz-Donawitz slag before using it for application in agriculture as a soil conditioner or as a fertilizer.