Simple Preparation of Lignin-Based Phenolic Resin Carbon and Its Efficient Adsorption of Congo Red

Abstract

Biomass porous carbon is a low-cost, environmentally friendly material with no secondary pollution and has great potential in the field of dye pollutant adsorption. In this work, we used lignin, a renewable resource abundant in nature, to completely replace phenol and develop a lignin-based phenolic resin carbon (LPFC) adsorbent with high dye removal capacity, high recyclability, and low production cost. The samples were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. Then the effects of adsorbent dosage (1 g/L, 2 g/L, 3 g/L, 4 g/L, and 5 g/L), temperature (30 °C, 45 °C, and 60 °C), initial dye concentration (100, 200, 300, 400, 500, 600, 700, and 800 mg/L), and pH (3, 4, 6, 8, 10, and 12) on the adsorption capacity were investigated during the adsorption process. The experimental results showed that the pore structure of LPFC was richer and more graphitized than that of phenolic resin carbon (PFC). The adsorption performance of LPFC on CR was better than that of PFC. The adsorption characteristics of LPFC were investigated from the adsorption isotherm and kinetic perspectives. The Langmuir isothermal adsorption model and the proposed second-order kinetic model were able to fit the adsorption data better. The adsorption process preferred monolayer adsorption, and the proposed second-order model predicted a maximum adsorption capacity of 425.53 mg/g. After five cycles, the removal of CR by LPFC only decreased from 92.1 to 79.2%. It can be seen that LPFC adsorbents have great potential in the field of wastewater treatment and can effectively realize the high-value application of lignin.