Disodium N,N-bis-(dithiocarboxy)ethanediamine: synthesis, performance, and mechanism of action toward trace ethylenediaminetetraacetic acid copper (II)

Abstract

A new effective multi-dithiocarbamate heavy metal precipitant, disodium N,N-bis-(dithiocarboxy) ethanediamine (BDE), was synthesized by mixing ethanediamine with carbon disulfide under alkaline conditions, and it was utilized for removing trace ethylenediaminetetraacetic acid copper (II) (EDTA-Cu) from wastewater. Its structure was confirmed by ultraviolet spectra, Fourier transform infrared spectra, scanning electron microscopy, thermogravimetric analysis, and elemental analysis. The removal performance of EDTA-Cu by BDE was evaluated according to BDE dosage, initial concentration, pH, and reaction time through single-factor experiments. With the optimized conditions of a pH range of 3-9, dosage ratio of BDE/Cu of 1:1, PAM dosage of 1 mg/L, and reaction time of 4 min, the removal efficiency of Cu(2+) was more than 98 % from simulated wastewater containing EDTA-Cu with initial concentrations of 5-100 mg/L. Treatment of actual EDTA-Cu wastewater showed that BDE performed superior effectiveness, and the average residential concentration of Cu(2+) was 0.115 mg/L. Besides, the stability of chelated precipitate and the reaction mechanism of BDE and EDTA-Cu were also introduced. The toxicity characteristic leaching procedure (TCLP) and semi-dynamic leaching test (SDLT) indicated that the chelated precipitate was non-hazardous and stable in weak acid and alkaline conditions. The BDE reacts with EDTA-Cu at a stoichiometric ratio, and the removal of Cu(2+) was predominantly achieved through the replacement reaction of BDE and EDTA-Cu.

Bottom-Up Synthesis of an Oligo-dithiocarbamate Chelating Precipitant and Its Direct Removal of Complexed Heavy Metals from Acidic Wastewater

“…As shown in Figure f, oligo-DTC prepared with NH 3 /DCE ratios of 3:1–5:1 presented typical UV–vis spectra of DTCs, with peaks at approximately 250 and 280 nm. , In contrast, oligo-DTC prepared with an NH 3 /DCE ratio of 1.5:1 or 2:1 exhibited relatively weaker oligo-DTC-related peaks, but there appeared by-product-related peaks at ∼330 and ∼230 nm. The UV–vis spectra of amination products (Figure S2) suggested that oligoamine obtained with NH 3 /DCE ratios of 3:1–5:1 was of higher purity, while oligoamine obtained with an NH 3 /DCE ratio of 1.5:1 or 2:1 contained undesired impurities.…”

“…Figure 5a showed that oligo-DTC could effectively remove Ni ions in various complexed forms. Figure 5b,c compared the performance of oligo-DTC with that of similar DTCs derived from ethyleneimine-based amines, including PEI−DTCs, 16,42 EDA−DTC, 26 and PIP−DTC. 43 Oligo-DTC was highly effective for Ni removal at both pH 2 and pH S11 and S12), in agreement with the results reported in the literature.…”

“…DTCs are generally synthesized by reactions of CS 2 and amines in the presence of NaOH. , Much attention has been paid to DTCs derived from dialkylamines, especially N , N -diethyldithiocarbamate. More recently, a series of DTC precipitants with better HM removal performance have been prepared from polyethyleneimines and various ethylene amines, such as ethylenediamine, piperazine, and tetraethylenepentaamine. ,,, However, since amines are quite expensive, these DTCs are not suitable for production and application on an industrial scale. It is highly desirable to prepare DTCs by a bottom-up method directly from ammonia.…”