Untitled

Abstract

Published experimental data on ethylenediaminetetraacetic acid (EDTA) biodegradation in the presence of ferric iron (Fe(III)) showed that rapid biodegradation of EDTA suddenly stopped, leaving a residual of unbiodegraded EDTA that was equal to the concentration of dissolved Fe(III). We hypothesize that slow kinetics for the dissociation of two iron-EDTA complexes--FeEDTA(-) and FeOHEDTA(2-)--sequestered the EDTA in a form that is biologically unavailable. To evaluate this hypothesis, we added to the biogeochemical model CCBATCH a new submodel for kinetically controlled complexation. CCBATCH simulations with kinetically controlled complexation for FeEDTA(-) and FeOHEDTA(2-) and the observed concentration of total dissolved Fe(III) accurately predicted the sudden cessation of EDTA biodegradation at the exact time shown experimentally. Our simulations also correctly predicted the observed residual EDTA concentration and the amounts of biomass and NH4+. Alternate explanations for the experimental results--strong equilibrium complexation of ferric iron and EDTA and precipitation of calcium and magnesium solids--could not capture the observed trends. This analysis using CCBATCH's new sub-model for kinetically controlled complexation shows that EDTA, once it becomes complexed with Fe(III), becomes biologically unavailable.

Separation of Magnesium Impurity from Nickel and Cobalt Mixtures Using Ethylenediaminetetraacetic Acid and Temperature Optimization

“…Similar observations regarding the slow kinetics of the EDTA complexation have been reported in other studies. Perez-Benito and Willett and Rittmann , noted that the complexation between EDTA and metal ions like Cr 2+ or Fe 3+ is a slow process. These findings underscore the importance of allowing sufficient time for complexation in processes where EDTA is used to separate metal ions, particularly in scenarios where the coprecipitation of metals needs to be minimized.…”

A New Method for Constant Estimate Stability of Complex With Edta

“…Embora o EDTA não seja tóxico aos humanos e a biota, a sua persistência no meio ambiente gera grandes preocupações, uma vez que o ligante apresenta a capacidade de gerar complexos solúveis com quase todos os metais da tabela periódica. Sua presença, em locais destinados ao descarte deliberado de metais tóxicos e radioativos, pode provocar a migração destas espécies para outras áreas, promovendo uma disseminação de espécies altamente nocivas aos seres vivos (Willett e Rittmann, 2003). Além do mais, EDTA livre também apresenta forte resistência à sua degradação por ação de bactérias e, por isso, pode acumular-se no solo e em corpos d`água.…”

“…Estudos têm apontado que a presença de EDTA livre é um dos maiores constituintes do rio Reno na Europa. Todavia, a maior concentração de EDTA é encontrada em regiões onde armas nucleares são produzidas (Willett e Rittmann, 2003…”

Mathematical modelling of trace element dynamics in anaerobic digestion environments

“…(1) organic substrates in AD (for example, VFAs); (2) humic substances; and (3) synthetic chelating agents (EDTA/NTA/EDDS). Here we discuss the general methodology developed in (Willet & Rittmann, 2003) and adopted in (Maharaj et al, 2019) to model TEs complexation in the ADM1 framework.…”