Simultaneous removal of toxic Pb(II) ions, poly(acrylic acid) and Triton X-100 from their mixed solution using engineered biochars obtained from horsetail herb precursor – Impact of post-activation treatment

Abstract

• Engineered biochars were prepared from horsetail herb by direct activation with steam. • Post-activation treatment was based on one- or two-steps washing using HCl and/or H 2 O. • The largest PAA and Pb(II) adsorption on solids was noted in double PAA/Pb systems. • Effective regeneration of applied adsorbents was possible using 0.1 M HNO 3 and NaOH. The horsetail herb was used as the precursor and was subjected to direct physical activation with steam (800 °C for 1 h). Next two variants of post-activation treatment was applied: (1) two-steps washing procedure, firstly with a hot 10% solution of HCl and later with demineralized water (HBA_HCl sample) and (2) one-step washing procedure only with demineralized water (HBA_H 2 O sample). The final products were characterized towards its textural structure, acid-base properties and surface morphology. The obtained biochars were used as adsorbents for simultaneous removal of hazardous lead(II) ions, poly(acrylic acid) (PAA) polymer and Triton X-100 nonionic surfactant from their mixed solution. It was shown that Pb(II) and PAA adsorbed amounts (from the single and mixed systems of adsorbates) have the greatest values on the HBA_HCl surface in the double PAA + Pb(II) system (148.8 mg/g and 195.8 mg/g, respectively) and in the triple PAA + TRT + Pb(II) system (183.3 mg/g and 187.7 mg/g, respectively). The nonionic surfactant desorption reaches high level (83–100%), independently from using desorption agent (HNO 3 or NaOH). Generally in the case of PAA, NaOH solution turned out to be more effective in adsorbent recovery process (especially from HBA_H 2 O surface), whereas in the case of Pb(II) ions desorption, HNO 3 is more effective desorbing agent (74–96% desorption).