Macroporous lignin adsorbents: A bio-sourced tool kit to defuse the Cr(VI) threat in wastewater

Amino-functionalised (triethylenetetramine) macroporous lignin monoliths were produced by curing an emulsion template containing untreated kraft black liquor with oxirane-crosslinkers. These lignin-based adsorbents were tested for the removal of Cr(VI) from water and synthetic waste water. A one-pot rout for their production is presented and their chemical and physical nature was investigated. Produced monoliths were tested in static and continuous adsorption experiments and chromium removal from water and synthetic wastewater was quantified via UV–vis spectroscopy. The nitrogen content of functionalised lignin monoliths reached up to 5.1 wt%, leading to adsorption capacities of up to 897 mg/g at pH = 2, as compared to non-functionalised lignin monoliths with a maximum adsorption capacity of 117 mg/g. The adsorption capacity of lignin monoliths produced is amongst the highest of bio-based materials presented in the literature.