Competitive adsorption of three phenolic compounds to hydrophilic urea-formaldehyde macroporous foams derived from lignin-based Pickering HIPEs template

Abstract

Hydrophilic urea-formaldehyde macroporous foams (UFMF) were simply synthesized by templating oil-in-water Pickering high internal phase emulsions (HIPEs) solely stabilized by lignin particles. Morphology and structure of the UFMF can be easily tailored by varying the experimental compositions of Pickering HIPEs and polymerization time. Due to their porous matrix, hydrophilic surface, and high content of binding groups (such as hydroxyl groups and carbonyl groups), as-prepared UFMF was adopted for the removal of three phenolic compounds (PCs) from aqueous solution. The influences of pH, solution temperature, contact time, and initial concentration of 2,4,5-trichlorophenol (2,4,5-TCP), 2,4,6-trichlorophenol (2,4,6-TCP) and 4-nitrophenol (4-NP) on adsorption capacity and competitive adsorption of multi PCs were investigated via the batch mode experiments. The adsorption kinetics and adsorption isotherms fit well by a pseudo-second-order model and Langmuir model, respectively. The max adsorption capacity of 2,4,5-TCP, 2,4,6-TCP and 4-NP at 25 °C are 116.3 mg g⁻¹, 78.74 mg g⁻¹, 29.41 mg g⁻¹, respectively, and their adsorption rate follows the order 2,4,5-TCP > 2,4,6-TCP > 4-NP. Moreover, the group type and position effects both influence the adsorption, and follow the order: 2,4,5-position substitution of chloride > 2,4,6-position substitution of chloride > 4-position substitution of nitro-group, showing that the substitution with the more groups has the higher adsorption affinity.