Microwave-assisted synthesis of coal fly ash-based zeolites for removal of ammonium from urine

Boitumelo Makgabutlane; Lebea N Nthunya; Nicholas Musyoka; Bongumusa S Dladla; Edward N Nxumalo; Sabelo D Mhlanga

doi:10.1039/c9ra10114d

Microwave-assisted synthesis of coal fly ash-based zeolites for removal of ammonium from urine

RSC Adv. 2020 Jan 14;10(4):2416-2427. doi: 10.1039/c9ra10114d. eCollection 2020 Jan 8.

Authors

Boitumelo Makgabutlane^{1

2}, Lebea N Nthunya³, Nicholas Musyoka⁴, Bongumusa S Dladla⁵, Edward N Nxumalo¹, Sabelo D Mhlanga^{1

2}

Affiliations

¹ Nanotechnology and Water Sustainability Research Unit, College of Science, Engineering and Technology, University of South Africa Florida 1709 Johannesburg South Africa.
² DST/MINTEK Nanotechnology Innovation Centre and SabiNano Pty Ltd, Mintek 200 Malibongwe Drive, Strijdom Park, Randburg 2194 Johannesburg South Africa sdmhlanga1@gmail.com smhlanga@sabinano.co.za.
³ Department of Chemical, Metallurgical and Material Engineering, Tshwane University of Technology Private Bag X680 Pretoria 0001 South Africa.
⁴ HySA Infrastructure Centre of Competence, Energy Centre, Council for Scientific and Industrial Research (CSIR) Meiring Naude Road, Brummeria Pretoria 0001 South Africa.
⁵ Department of Chemistry, College of Science, Engineering and Technology, University of South Africa Florida 1709 Johannesburg South Africa.

Abstract

Zeolites synthesized from biomass waste materials offer a great opportunity in the sustainable utilization of the waste. In this work, energy-efficient processes (i.e. microwave and ultrasound irradiation) were used to synthesize pure phase sodalite (zeolite) from coal fly ash obtained from a power plant in South Africa. The pure-phase sodalite was obtained with a comparatively higher surface area (16 m² g^-1) and cation exchange capacity (2.92 meq. g^-1) with 40 min total reaction time. The removal of ammonium from urine was carried out using (i) the coal fly ash-derived sodalite, (ii) raw coal fly ash and (iii) a commercially available natural zeolite (clinoptilolite). The pure phase sodalite exhibited the highest removal efficiency of about 82% and 73% in synthetic and real hydrolyzed urine respectively. The adsorption process followed the pseudo second-order kinetic model and the Freundlich adsorption isotherm, indicating that the adsorption process occurred on a heterogeneous surface.