Synthesis of a biobased resin and its screening as an alternative adsorbent for organic and inorganic micropollutant removal

Abstract

The sol–gel route was used to synthesize a biophenolic resin from a blend of Kraft black liquor and condensed tannin. The biobased resin has an amorphous structure and diversified surface functional groups. The biomaterial thermal stability was improved by Kraft black liquor, which increased the fixed carbon yield by 19.78% in an oxidant medium and 9.07% in an inert medium. Moreover, the presence of fixed carbon and char is positively related to the material flame retardant property. Additionally, impedance measurements were used to understand the physical phenomena occurring at the polymeric matrix's interface and the material's final properties. The biobased resin characterization and the considerable increase in the presence of micropollutants in surface and water bodies suggest the new biomaterial application in the adsorption process. Thus, its adsorption capacity toward several organic and inorganic micropollutants and its effectiveness in complex water matrices were evaluated. Methylene blue was used as a model compound to assess the influence of the resin composition on the adsorption capacity, and the type H isotherm indicates the high affinity of the biobased resin toward the micropollutant. The adsorption occurs in multilayer by intermolecular interaction and electrostatic forces. The amount of Kraft black liquor favored the adsorption, and the adsorption capacity was greater than 1250 mg g⁻¹. When inorganic compounds were evaluated, the carboxyl and phenol groups favor the biomaterial affinity toward metal ions. Cu²⁺ and Ni²⁺ were completely removed from the contaminated water, and the adsorption capacity of the other inorganic compounds was: Pb²⁺ (36.97 mg g⁻¹), Al³⁺ (22.17 mg g⁻¹), Ba²⁺ (12.76 mg g⁻¹), Ag¹⁺ (33.85 mg g⁻¹), and Fe²⁺ (19.44 mg g⁻¹). In contrast, the adsorption capacity of the organic micropollutants was: 2,4-D (3.09 mg g⁻¹), diuron (5.89 mg g⁻¹), atrazine (2.71 mg g⁻¹), diclofenac (2.04 mg g⁻¹), caffeine (5.79 mg g⁻¹), acetaminophen (4.80 mg g⁻¹), methylene Blue (106.66 mg g⁻¹), and methyl orange (30.48 mg g⁻¹). The results pointed that the adsorption efficiency of organic micropollutants increases with the distribution coefficient (logD), indicating the biobased resin affinity toward more lipophilic compounds and ionized species.