Performance of nanosilver/silver oxide in sorbing phosphate from synthetic greywater

Abstract

Silver/silver oxide nanoparticles were impregnated on polyurethane foam to form a newfangled adsorbent (PFA) for reducing the phosphate content in the synthetic greywater. The characterisation studies revealed the spherical shape of nanoparticles with size 44 nm to 75 nm, along with the elemental presence on PFA with their proportionate weight%. The favourable functional group for sorbing phosphate ions by PFA was verified by the Fourier transform infrared spectroscopic analysis and the crystallographic structure of PFA was revealed in X-ray diffraction studies. The surface area of the sorbent by the Brunauer–Emmett–Teller study was observed to be 1.80 m2/g. The point of zero charge of PFA was found to be 8.3. The experimental studies under batch mode showed that at optimum conditions (contact time 6 h, pH 6.5, and sorbent dosage 3.75 g/L), PFA could sorb 38.05% of phosphate from synthetic greywater having 155 mg/L of phosphate. The PFA showed reusing capacity and the phosphate removal efficacy after five adsorption/desorption cycles was 23.58%. Inductively coupled plasma optical emission spectroscopic results revealed the elution of silver ions from PFA during synthetic greywater treatment. This indicated the loss of favorable phosphate sorption sites which resulted in reduced efficacy and limited the use of PFA in water/wastewater treatment.

Keywords: Adsorption, impregnation, kinetics, polyurethane foam, phosphate, silver/silver oxide nanoparticles