Leaching of chromium (Cr) and lead (Pb) in surface sediments from Meycauayan River in Bulacan using oxalic acid (OA) and N,N-BIS (Carboxymethyl)-L-Glutamic acid tetrasodium salt (GLDA)

ABSTRACT: Heavy metals pose significant threats to soil, air, and water systems. Their presence in surface sediments, particularly in the Meycauayan River in the Philippines, is alarming due to their toxicity, persistence, and tendency to accumulate in the organisms. Lead (Pb) and chromium (Cr) are particularly prevalent in this river. Thus, the harmful effects brought by the high heavy metal content in these surface sediments require an immediate solution. This study focused on using a new type of leaching solution, GLDA and oxalic acid, to effectively leach Pb and Cr from surface sediments. The sediments collected along the Mecauayan River were first tested for heavy metal using AAS and ICP-OES and was characterized according to its contamination factor and potential ecological risk. Results showed that the sediments contained 89.6 mg/kg Pb, 54.1 mg/kg Cr, 0.63 mg/kg Cd, 2.3 mg/kg As, and <0.1 mg/kg Hg. The chemical leaching process was then conducted by varying GLDA-OA ratio in the leading solution, S/L ratio, and leaching time. After the chemical leaching experiments, the maximum number of metals leached is 6.31% for Cr and 27.21% for Pb. With the use of the main effects plot, the optimum parameters were determined to the 20% GLDA-80% OA ratio in the leaching solution, 5:10 S/L ratio, and 120 minutes of leaching time, with the maximum yield of 6.24% for Cr and 27.01% for Pb. Among these parameters, it was revealed that the ratio of GLDA and OA in the leaching solution has the highest effect on heavy metal leaching, having an 80.04% contribution. Furthermore, the results from the analysis of variance (ANOVA) revealed that the ratio of GLDA-OA in the leaching solution factor has a significant statistical association with the response factor (percent metal leached). The findings implied that the leaching solution (mixture of GLDA and OA) was not effective in leading lead and chromium in the surface sediments along the Meycauayan River due to the low percentage of metal leached. Thus, it is recommended to investigate other parameters that may have a greater effect on leading and use other acids together with GLDA to possibly produce a better leaching solution.

Filipiniana