Spectrophotometric Determination of Trace Amounts of Pentachlorophenol in Water after Preconcentration with Mixed Oxide of Iron(III) and Magnesium

Abstract

A simple and rapid method for the determination of trace amounts of pentachlorophenol(PCP) in water was proposed. The proposed adsorbent was prepared as follows; a suspension of mixed hydroxide, which was prepared by mixing 20mL of 1mol dm^-3 of iron(III) chloride and 30mL of 4mol dm^-3 of magnesium chloride, diluting the mixture to 1dm³ with distilled water, and precipitating mixed hydroxide with sodium hydroxide, was separated through filter paper(No.2, 12cm) under suction. The residue was dried at 450°C for 30min in an oven. A 0.6g portion of adsorbent was added to 200mL of test solution. After adjusting the pH from 11 to 12, the suspension was stirred for 60min and filtered with a 1μm membrane filter. The residue on the filter was stirred in 1.5mL of 5mol dm^-3 of sulfuric acid and 10mL of 1mol dm^-3 of sodium sulfate, and was extracted with 4mL of 1-pentanol. The absorbance of the extract was measured at 215nm against 1-pentanol. PCP ranging from 10 to 80ppb could be determined. NH₄⁺, Ca²⁺, CO₃^2-, SO₄^2-, BO₃^-, F^-, SiO₄^2- and PO₄^3- as much as 1×10^-3mol dm^-3 did not interfere, but up to 1×10^-4mol dm^-3 of NO₂^- and NO₃^- interfered. Molecular sieves 5A coated with mixed oxide of iron(III) and magnesium was applied to the chromatographic separation of chlorophenols.