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 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_H2O 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 (HNO3 or NaOH). Generally in the case of PAA, NaOH solution turned out to be more effective in adsorbent recovery process (especially from HBA_H2O surface), whereas in the case of Pb(II) ions desorption, HNO3 is more effective desorbing agent (74–96% desorption).