Figure 5From: Direct production of biodiesel from high-acid value Jatrophaoil with solid acid catalyst derived from ligninEnergy-dispersive x-ray spectrometry (EDX) spectra of sulfonated Kraft lignin chars (A) without phosphoric acid pretreatment and (B) with phosphoric acid pretreatment (catalyst). Figure 5 shows the EDX spectra for the Kraft lignin char with and without acid treatment and the presence of sulfonic group in the char.Back to article page