An AlgaSORB Column for the Quantitative Sorption of Arsenic(III) from Water Samples

This study examines a new Scytonema-based biosorbent (AlgaSORB-scy) using column chromatography for the biosorption of total inorganic arsenic [As(III) and As(V)] from aquatic samples. The AlgaSORB-scy was prepared by immobilizing a cyanobacterial biofilm (Scytonema-dimethyl-formamide slurry) over a polymer-modified silica gel and then characterized for stability and sorption/elution conditions under dynamic equilibrations followed by differential pulse polarographic detection. The sorbent exhibited a 100% affinity for As(III) in a multi-elemental solution [in the absence of As(V)] at pH 6.9 and a flow rate of 1 mL min-1 giving rise to a preconcentration factor as high as 44-fold. The interference caused by As(V) in the sorption of As(III) on AlgaSORB-scy necessitated the pre-reduction of As(V) into As(III) by sodium sulfite. The biosorbent was found to be suitable for total arsenic enrichment in the form of As(III) species and demonstrated a better endurance with a recyclability of up to 59 cycles of sorption-elution. The polymeric spacer between the cyanobacterial biofilm and the silica gel enabled the biofilm monolayer to be held firmly onto a solid support and be accessible for quantitative arsenic uptake without encountering any problems of interfacial overlapping, re-adsorption, or matrix effects in the drinking water supplied.