A review of prospects and current scenarios of biomass co-pyrolysis for water treatment

Abstract

With ever-growing population comes an increase in waste and wastewater generated. There is ongoing research to not only reduce the waste but also to increase its value commercially. One method is pyrolysis, a process that converts wastes, at temperatures usually above 300 °C in a pyrolysis unit, to carbon-rich biochars among with other useful products. These chars are known to be beneficial as they can be used for water treatment applications; certain studies also reveal improvements in the biochar quality especially on the surface area and pore volume by imparting thermal and chemical activation methods, which eventually improves the uptake of pollutants during the removal of inorganic and organic contaminants in water. Research based on single waste valorisation into biochar applications for water treatment has been extended and applied to the pyrolysis of two or more feedstocks, termed co-pyrolysis, and its implementation for water treatment. The co-pyrolysis research mainly covers activation, applications, predictive calculations, and modelling studies, including isotherm, kinetic, and thermodynamic adsorption analyses. This paper focuses on the copyrolysis biochar production studies for activated adsorbents, adsorption mechanisms, pollutant removal capacities, regeneration, and real water treatment studies to understand the implementation of these co-pyrolyzed chars in water treatment applications. Finally, some prospects to identify the future progress and opportunities in this area of research are also described. This review provides a way to manage solid waste in a sustainable manner, while developing materials that can be utilized for water treatment, providing a double target approach to pollution management.

Keywords: Activation; Adsorption; Biomass; Co-pyrolysis; Water treatment.

Fig. 1

SCOPUS results for co-pyrolysis papers in literature

Fig. 2

Schematic diagram of wastes to adsorbents for water treatment

Fig. 3

Before and after adsorption (A) XRD spectra. (B) FTIR spectra

Fig. 4

FTIR spectra of fresh and used co-pyrolyzed char

Fig. 5

Before and after adsorption (A) XRD spectra (B) FTIR spectra

Fig. 6

XPS spectra of fresh and used co-pyrolyzed char

Fig. 7

Regeneration studies of water treatment using co-pyrolyzed chars