Abstract
The present study describes extraction of chromium(VI) through supported liquid membrane (SLM), Celgard 2400, which was impregnated with trioctylphosphine oxide (TOPO) dissolved in toluene. The stripping phase was comprised of diphenylcarbazide (DPC) in sulfuric acid (H2SO4) whereas the feed phase consists of potassium dichromate (K2Cr2O7) and hydrogen peroxide (H2O2). The effects of concentrations of chromium, TOPO, DPC, and H2SO4 have been studied in order to evaluate the transport efficiency of chromium(VI) ion. The optimum experimental conditions for the chromium(VI) extraction were established as follows: 19.2 × 10−4 mol L-1 chromium ion, 1.5 mol L-1 H2O2 concentration in the feed phase, 0.1 mol L-1 TOPO concentration in the membrane phase and 0.001 mol L-1 DPC and 1.5 mol L-1 H2SO4 as stripping phase. The measurements of percent recovery, distribution coefficient, flux and permeability were made at the given optimized conditions. The extraction time and membrane stability were also investigated. Extraction efficiency of 80% was recorded in 180 min and the SLM system was found stable up to 10 days. The optimized SLM system was then applied on the paint industry wastewater; about 80% of chromium(VI) was successfully removed from the wastewater.
Highlights
The extensive industrialization has caused environmental pollution at alarming level
The limiting value of extraction of chromium at 0.1 mol L-1 trioctylphosphine oxide (TOPO) may be attributed to increased viscosity of TOPO solutions which hampers the movement of metal ions through the membrane
The present study demonstrates that CrVI can be efficiently and selectively transported through the supported liquid membrane by using TOPO as a carrier
Summary
The extensive industrialization has caused environmental pollution at alarming level. The water near industrial sites is generally polluted by mixture of metals and organic compounds. Among many other metal pollutants chromium is one of the most serious threats to the living organisms. The total worldwide chromium production is about 16.4 million tons, while 15.38 million tons are produced in South Africa, India, Kazakhstan, Zimbabwe, Finland, Brazil and Turkey.[1] Chromium compounds are mainly used in industrial processes, such as corrosion control, oxidation process, leather tanning process, electroplating, metallurgy, cement, textile dying, paper making, ink, paints and pigments, and photographic industry.[2] Due to extensive use of chromium, various industries are discharging a significant concentration of chromium without prior treatment of the waste. Chromium concentration of 0.25 mg L-1 is responsible for the serious threats to aquatic as well as human life.[1]
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