Coffee pulp and husk-derived hydrochars and biochars adsorb polyphenols and pesticides from wastewater

Coffee processing generates significant amounts of wastewater rich in organic compounds and sometimes also pesticides. This poses environmental challenges for producing regions. This study aimed to assist coffee producers by providing local waste management solutions by examining the adsorption efficiency of hydrochars and biochars derived from coffee pulps (CP) and coffee husks (CH) in removing polyphenols and pesticides from coffee processing wastewater (CPWW). These materials were tested for the adsorption of selected polyphenols and pesticides from CPWW. Hydrochars exhibited high removal efficiencies for polyphenols (up to 100%), primarily via hydrogen bonding, while biochars effectively adsorbed hydrophobic pesticides (removal efficiencies up to ~75%) through hydrophobic interactions. Adsorption data fitted the Freundlich isotherm, indicating multilayer adsorption, and kinetic analyses suggested complex mechanisms involving both physisorption and chemisorption. These findings demonstrate the potential of coffee waste-derived chars to serve as sustainable adsorbents for mitigating pollution from CPWW, offering a promising local waste management strategy in coffee-producing countries