It is becoming a necessity to provide resource constrained small public water utilities with diverse, cost-effective, low-technology and sustainable alternatives for removing arsenic and other contaminant clusters in order to provide safe drinking water. Chitosan-coated Diatomaceous Earth (CCDE), was prepared by coating natural diatomaceous earth with chitosan. The chitosan to DE percent mass ratios were varied between 0 and 50%, and the effect of chitosan content on the effectiveness of the resulting hybrid biosorbent was evaluated. The CCDE was characterized by assessing its microstructure, surface functional groups, specific surface area, morphology, elemental composition, surface of zero charge, acidity/ alkalinity and thermal stability. Batch bottle point isotherm equilibrium experiments were conducted to study the uptake of As(V) by CCDE from a solution of disodium hydrogen arsenate heptahydrate (Na2HAsO4, 7H2O) in MilliQ water adjusted to a desired pH. The effects of the synthetic water’s initial pH were also evaluated. As(V) in samples was measured as total As by inductively-coupled plasma atomic emission spectroscopy. The experimental results indicated that the amount of As(V) adsorbed increased with chitosan content of CCDE while the treated water filterability reduces. The CCDE with 30% chitosan content (CCDE30) is optimal for removing As(V) from drinking water. As(V) uptake decreased with increasing pH, and the optimal range between 5 and 6. The Isotherm data fit both Langmuir and Freundlich models. The isotherm data indicated that CCDE30 could be a viable alternative adsorbent for As(V) for small system applications because of its effectiveness, ease of preparation, affordability, and technology sustainability. In a comparative study, CCDE30 is as effective as Bayer’s Bayoxide E33® for As removal at observed occurrence levels through major parts of the U.S.A. CCDE30 showed 3 to 4 times lesser capacity than E33®, but equivalent if expressed in mg/g of Chitosan. The CCDE30 presents the added benefit for multiple regenerations.

Facile preparation, characterization and application of chitosan-coated natural diatomaceous earth for the removal of arsenic (V) from drinking water

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