Sustainable design of lignin-based spherical particles with the use of green surfactants and its application as sorbents in wastewater treatment

Abstract

Biopolymer-based particles may be prepared using a soft-template method. Surfactants are among the most popular soft templates, but synthetic surfactants may be toxic or hazardous for humans and the environment. In this research, for the first time, natural surfactants were used to prepare spherical and doughnut-like particles. Two different powder types were prepared with the use of kraft lignin and natural extracts, which were derived from Saponaria officinalis L. and soap nuts of the Sapindus mukorossi tree, which contain saponins as surface active agents. A detailed characterization of the synthesized bio-based spheres was made with the use of scanning electron microscopy (SEM), transmission electron microscopy (TEM) images, dispersion analysis (PSD, PdI), Fourier transform infrared (FTIR) spectra, determination of porous structure parameters (low-temperature N2 sorption), elemental analysis (EA) and thermal stability analysis (TGA/DTG). Moreover, their sorption abilities with respect to pharmaceutically active cetirizine dihydrochloride (as reference compound) was tested. The adsorption efficiency around 90% for both materials was observed at pH 6.2 with the concentration of 10 mg/L of an active compound. Moreover, the equilibrium was reached after 240 min and it was concluded, that material prepared with the use of Sapindus mukorossi extract is a more efficient sorbent. The use of natural precursors may reduce environmental hazards and unnecessary waste, and the prepared particles may find future applications as novel eco-friendly materials, for example as adsorbents of harmful substances and in enzyme immobilization.