Techno-Economic Evaluation of Iron and Aluminum Coagulants on Se(IV) Removal

Abstract

Research on selenium pollution in natural waters is continuous and discouraging. In this study, coagulation/precipitation was applied with the use of Fe(II), Fe(III), and poly-aluminum chloride (PACl) salts for Se(IV) removal at concentration range 10–100 μg Se(IV)/L that is commonly found in drinking waters. Prehydrolyzed Fe(III)-FeCl3 delivered the best uptake capacity (Q10 = 8.9 mg Se(IV)/g Fe(III) at pH 6) at the residual concentration equal to the drinking water regulation limit of 10 μg/L. This was much higher than the efficiencies achieved when applying the other coagulants: i.e., Q10 = 7.3 mg Se(IV)/g Fe3+-FeClSO4, Q10 = 6.4 mg Se(IV)/g prehydrolyzed Fe(III)-Fe2(SO4)3 and 0.7 mg Se(IV)/g Al-PACl at pH 6, and Q10 = 0.45 mg Se(IV)/g Fe(II) at pH 7.2. Comparing the different sources of Fe(III), it is apparent that Se(IV) uptake capacity is inhibited by the presence of SO42− in crystal structure of prehydrolyzed Fe2(SO4)3, while prehydrolyzed FeCl3 favors Se(IV) uptake. Temperature effect data showed that coagulation/precipitation is exothermic. In techno-economic terms, the optimal conditions for Se(IV) removal are coagulation/precipitation at pH values lower than 7 using prehydrolyzed Fe(III)-FeCl3, which provides a combination of minimum sludge production and lower operating cost.

A Bibliometric Analysis of Research on Selenium in Drinking Water during the 1990–2021 Period: Treatment Options for Selenium Removal

“…Aluminum coagulants, such as AlCl 3 or poly-aluminum chloride PAC, are very commonly used for water treatment too, since Al cations hydrolyze quickly and form abundant hydroxide precipitates in situ, which can act in a similar way to their homologous ferric compounds. Nevertheless, the research about the use of aluminum coagulants for selenium removal has demonstrated that the use of ferric compounds was preferred, since they were much more efficient [223,224]. Nevertheless, the performance of the coagulation process can be enhanced with the addition of commercially available polymeric flocculants, which enhanced the removal of selenium [225].…”

Selenite Removal from Water

“…The experimental results (Figure 1) for Se(IV) coagulation/precipitation by Fe(III) at pH 7 delivered a Q10 value of 3.2 μg Se(IV)/mg Fe(III) with the data best fitted in a BET adsorption model (Table 4) that indicated the Se(IV) removal by a physisorption process [28]. In order to estimate the cost of treatment, the Fe(III) dose required for the removal of Se(IV) from natural water at an initial concentration of 100 μg Se(IV)/L and pH 7 can be calculated as follows:…”

Effect of Alum Dose in the Coagulation Process for Decreasing the Pollutant in the Palm Oil Mill Effluent: Experimental and Kinetic Analysis

“…Reaksi adsorbsi pada proses koagulasi termasuk reaksi endotermis atau reaksi eksotermis tergantung jenis adsorben dan adsorbat. Proses koagulasi menggunakan koagulan garam Fe(II), Fe(III) dan poly-aluminium chloride untuk mengadsorb Se(IV) adalah eksotermis (Kalaitzidou et al, 2020). Proses koagulasi menggunakan koagulan alam Leucaena crude extract untuk mengadsorb Congo red adalah endotermis (Kristianto et al, 2022).…”