Capacity and mechanisms of ammonium and cadmium sorption on different wetland-plant derived biochars

Recovery of nutrients from biogas digestate with biochar and clinoptilolite

“…Biochar has been suggested as a sorbent for ammonium (TaghizadehToosi et al, 2012a;Hale et al, 2013;Gai et al, 2014;Carey et al, 2015;Cui et al, 2016), orthophosphate (Hollister et al, 2013;Sarkhot et al, 2013;Xu et al, 2014) and organic contaminants (Ahmad et al, 2014;Mohan et al, 2014;Wang et al, 2015b) removal from various wastewaters. Chemical activation of biochar has been shown to increase the oxygen-containing functional groups (Xue et al, 2012;Wang et al, 2015a) which affects the cation sorption on biochar, and orthophosphate removal due to cation bridge bonding (Lin et al, 2012;Qian et al, 2013).…”

“…Cation U-BC DW-BC H 2 SO 4 -BC NaOH-BC H 2 O 2 -BC exchange was used as one possible mechanism to explain ammonium removal (Sarkhot et al, 2013;Gai et al, 2014;Cui et al, 2016). Sarkhot et al (2013) observed the release of Ca + ions and Cui et al (2016) reported that Mg 2+ and Ca 2+ were released into the liquid solutions whereas NH4 + was removed, therefore concluding that these cations play an important role in the sorption of ammonium. K + release from biochar ( Figure 3.2a) was observed, which could be due to cation exchange with NH4 + in the synthetic solution.…”

“…A higher ammonium removal by acid and base-treated chars could be explained by cation exchange: cations in biochar were replaced with H + and Na + ions as a result of H2SO4 and NaOH treatments, and thereby H + and Na + could easily be exchanged with NH4 + ions, since NH4 + is more competitive than the aforementioned ions (Cui et al, 2016). Activation of biochar significantly affected ammonium removal (p<0.001) from the liquid fraction of digestate (Figure 3.1b).…”

“…Another explanation for higher ammonium removal could be struvite (MgNH4PO4.6H2O) precipitation due to higher concentrations of magnesium in the liquid fraction of digestate. Cui et al (2016) reported the formation of struvite when biochar is used to remove ammonium from liquid solutions.…”

“…The potential of biochar to recover nutrients from liquid wastes with high nutrient concentrations, such as dairy manure and ruminant urine, has also been discussed in the literature (Taghizadeh-Toosi et al, 2012;Sarkhot et al, 2013). It has been suggested that the removal of ammonium by biochar is mainly controlled by interactions between ammonium ions and oxygen-containing functional groups, such as carboxylates or carboxylic acids, on the biochar surface (Wang et al, 2015a;Cui et al, 2016). Several studies have suggested that pyrolysis temperature is an important parameter affecting biochar properties (Ahmad et al, 2014;Lehmann & Joseph, 2015).…”