Nuclear chemistry

Wastewater

Adsorption

Salt (chemistry)

Engineering

Chitosan

Magnesium

Inorganic chemistry

Sulfate

Langmuir adsorption model

Waste management

Environmental engineering

Chloride

Organic chemistry

Phosphonium

Desorption

Phosphonium salt

Chemistry

Carbohydrate Polymers

Adsorption is a commonly used method for industrial wastewater treatment because of its low-cost, easy operation and high efficiency. In this work, chitosan was crosslinked and functionalized with a low-cost phosphonium salt, tetrakis(hydroxymethyl)phosphonium sulfate (THPS), to enhance its adsorption capacity for Cr(VI). The novel phosphonium-crosslinked chitosan (PCC) was characterized using elemental analysis, XRF, FTIR, NMR and SEM-EDX. At pH 6, PCC had a higher Langmuir equilibrium constant than the unmodified chitosan (0.19 ± 0.02 L mg−1 versus 0.0044 ± 0.0005 L mg−1) and PCC demonstrated higher adsorption capacity than chitosan at equilibrium Cr(VI) concentrations below 120 mg L−1. Additionally, magnesium sulfate or magnesium chloride was shown to desorb Cr(VI) and recycle PCC. When treated with THPS, chitosan is activated for Cr(VI) adsorption at pH 6; therefore, PCC can be used in wastewater treatment over a wider pH range than chitosan.

Phosphonium-enhanced chitosan for Cr(VI) adsorption in wastewater treatment