Circular economy based landfill leachate treatment with sulphur-doped microporous biochar. (1st April 2021)

• Record Type: Journal Article
• Authors: Pap, Sabolc; Boyd, Kenneth G.; Taggart, Mark A.; Turk Sekulic, Maja
• Is Part Of: Waste management. Volume 124(2021)
• Page Start: 160
• Page End: 171
• Publication Date: 2021-04-01
• Subjects: Lead pollution -- Adsorption mechanisms -- Instrumental characterisation -- Response surface methodology -- Reusability; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2021.01.037
• Languages: English
• ISSNs: 0956-053X

Abstract

Graphical abstract: Highlights: Sulphur-doped microporous biochar was synthesised by pyrolysis and functionalisation. Lead removal efficiency was optimised using response surface methodology. Adsorption mechanisms were governed by inner and outer-sphere complexation. Biochar displayed high adsorption capacity (44.92 mg/g) and good reusability. Biochar possessed excellent selectivity toward Pb(II) even in landfill leachate samples. Abstract: There is now increasing interest in the creation of a more 'circular economy', with a particular aim to eliminate waste – by design, within which products are optimised to be reused, restored or returned. Here, a sulphur functionalised microporous biochar was synthesised from an abundant biomass waste material (cherry kernels), for the selective removal of Pb(II) from landfill leachate as a representative heavy metal. The production process utilises renewable waste material and removes toxic chemicals. Characterisation of the biochar showed that pyrolysis and functionalisation formed an adsorbent with a microporous structure and rich surface chemical functionality. The adsorption process was optimised using a 'response surface methodology – Box-Behnken Design'. Lead removal efficiency approached 99.9% under optimised experimental conditions, i.e., where the solution pH was 6.0, the biochar dose was 4.0 g/L and the contact time was 47 min. The adsorption process was best described using a Freundlich model. The maximum amount of Pb(II) adsorbed was 44.92 mg/g. The main adsorption mechanisms occurred through outer-sphere (electrostatic attraction) and inner-sphere complexation. Desorption studies showed that three successful regeneration cycles (with acidic deionised water) could be used post pyrolysis. The biochar removed 97% of Pb(II) from landfill leachate samples, as compared to 9.4%, and 7.6% for two commercial activated carbon adsorbents. These findings demonstrate the high selectivity of this biochar towards Pb(II) and its applicability even in the presence of high concentrations of many potentially interfering inorganic and organic ions and compounds.