A new hybrid (polymer/inorganic) fibrous sorbent for arsenic removal from drinking water

摘要

It has been established that fibrous polymeric ion exchangers can be impregnated with nanoparticles of hydrated ferric oxide (HFO) which serves as a selective sorbent for As(Ⅲ) and As(Ⅴ) species from aqueous solutions. The screening studies have shown that the largest amount of Fe(Ⅲ) can be loaded into a weak base anion exchanger with ternary amino groups (up to 1.4 mmol Fe/gram of dry fiber). The fibrous composite sorbent on the base of such anion exchanger possess a high selectivity toward both As(Ⅲ) and As(Ⅴ) species combined with a high sorption capacity (～2.9 g As/kg till As concentration in outlet solution becomes more than 10 μg/L). The sorbent does not release Fe into contacting solution and does not require backwashing in column operations. Its specific feature is extremely high rate of the sorption processes. The process rate is controlled by diffusion of the arsenic species into HFO particles uniformly spread in the fiber. The half process time appeared equal 23 s which allows column operation with empty bed contact time down to 10 s. The sorption of As(Ⅲ) at pH values admissible for drinking water is not affected by the foreign anions (Cl~-,SO_4~(2-), H_2 PO_4~-/HPO_4~(2-)). Sorption of As(Ⅴ) decreases with phosphates concentration increasing. Column experiments with model and natural waters containing As in concentrations 50-100 ppb have shown that the new sorbent can be used for production of small water household filters with the filtering bed volume about 0.5 L. The filter allow purification of 200 L of water per hour and obtaining 2.5-5 tons (5000-10000 bed volumes) of purified from As(Ⅲ) and As(Ⅴ) water without correcting pH and pre-oxidation of As(Ⅲ). The field experiment on purification of natural water containing 60 ppb of As allowed purification of 10000 bed volumes of water to 10 ppb of As in the effluent.