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.
Highlights
Water quality degradation is a crucial matter of global concern
In techno-economic terms, the optimal conditions for Se(IV) removal are coagulation/precipitation at pH lower than the saturation one (pHs) values lower than 7 using prehydrolyzed Fe(III)-FeCl3, which provides a combination of minimum sludge production and lower operating cost
Long-term consumption of drinking water that contains high concentrations of toxic elements is related to carcinogenesis, chronic diseases, vital organ destruction, and increased mortality [1]
Summary
Water quality degradation is a crucial matter of global concern. Long-term consumption of drinking water that contains high concentrations of toxic elements is related to carcinogenesis, chronic diseases, vital organ destruction, and increased mortality [1]. The most coagulation/precipitation treatment processes are based on the reduction of selenite to elemental selenium using mostly sulfur-based reductants or zero-valent iron (ZVI) [4,15,18] This method requires posttreatment to completely remove the residual reductant. Almost all studies have focused on high initial concentrations in a distilled water matrix without evaluating other co-existing ions These proposed treatment techniques are efficient only at acidic pH ranges, requiring a posttreatment process, strongly modify water quality, and do not achieve residual concentrations below the DWRL of 10 μg/L. Coagulation/precipitation is traditionally applied for drinking water treatment since it offers significant advantages such as high removal efficiencies using low-cost coagulants and is effective at a wide range of pH values [22]. To the best of our knowledge, no previous research has estimated the Q10 value at the pH range of 6–8, which would provide realistic data applicable for the scale-up of the coagulation/precipitation process and to estimate the treatment cost for selenite removal
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
