Notice of RetractionDefluorination from groundwater in rural China by nanofiltration technology: Performance and multistage arrangement

Notice of Retraction

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A laboratory-scale experiment was conducted to investigate the performance of defluorination from groundwater by nanofiltration (NF) technology, to find out the potential reason of ions rejection by NF, and also to study the feasibility of multistage NF membranes arrangement for defluorination consideration of the product water quality/flow, as well as the water recovery. NF has an excellent character of selective removal, and can keep the potentially beneficial ions to human health in the product water. In addition, F" concentration in product of a single stage of NF membrane system can meet the national drinking water standard of China in rural area when the feed F" concentrations are below 3.40 mg L"1. Hydration energy of cation or anion is found to be one reason that has the strong influence on rejection efficiency with sequence SO₄^2- > Mg²⁺ > Ca²⁺ > F^- > CI^- > No₃^- > Na⁺ during NF separation. With the multistage (double or trinary) NF system, the total water recovery rate and the product water flow are both improved significantly, and the potable water that contains F^- concentration less than 1.2 mg L^-1 can also be achieved. Therefore, membranes arrangement staging in series with double staging or trinary staging is feasible.