MICB, a new sorbent for arsenic removal from wastewaters

Characteristics of the sorbent

	As shown on the photo, chitosan beads (average diameter: 2.2 mm) can be packed easily in column reactor and used in a flow system to remove arsenic from contaminated wastewater.
	As (V) is removed between pH 2.5 and 4. Maximum uptake capacity is 200 mg As/g Mo or 12 g As/L of wet beads.
	As(III) can be removed in a lower extent in the same pH range. Maximum uptake is 80 mg/g Mo.
	High concentrations of Cl^{- ,} NO₃^- , SO₄^2-, don't affect the removal efficiency.
	Arsenic sorption is very selective towards metal ions present in solution like Pb²⁺ or Cu²⁺ even if they are in high concentrations (0,1 mol.L^-1).
	Phosphate ions depressed greatly arsenate sorption. On the other hand, silicate ions affect slightly the uptake efficiency even in high concentration.
	The sorbent has been improved regarding molybate release during the sorption process and this release is ranging between 0,5 and 1 %.
	After adsorption, arsenate ions can be selectively stripped from the sorbent using a 0.1 molar orthophosphoric acid solution.
	The spent sorbent can after by reuse for many adsorption-desorption cycles.

As(V) sorption mechanism

Molybdate ions are distributed in the whole volume of the porous sorbent as polynuclear species (Mo7). Before As(V) sorption,phosphates are complexed with molybdate. When the adsorption process takes place, they are exchanged with arsenate ions and are released in the solution.This reaction is possible because the binding constant of Mo-As complex is much more important than Mo-P complex.

Characteristics of MICB

	Volumic mass: 1130 mg per liter
	Moisture: 91 %
	Dry weight:250 g per liter rigidity, acid resistance
	Operating temperature 4 °C - 60 °C
	Arsenic sorption capacity at saturation: 12 g As(V) per liter - 4,5 g As(III) per liter
	Cost: 30 $ per liter