Residues from the processing of cassava roots (Manihot esculentaCrantz), or cassava peels, are evaluated as chemically modified adsorbents with H₂O₂, H₂SO₄, and NaOH, in the removal of metal ions Cd(II), Pb(II), and Cr(III) from contaminated water. Modified adsorbents were chemically characterized for their chemical composition andpHPZC(point of zero charge), while adsorption tests determined the best conditions of pH, adsorbent mass, and contact time between adsorbent and adsorbate in the process of removal of the metal ions. Isotherms obtained from the preliminary results were linearized by Langmuir’s and Freudlich’s models. The thermodynamic parameters, such asΔH,ΔG, andΔS, were also evaluated. The modifying solutions proposed were effective in the modification of adsorbents and resulted in high capacity sorption materials. Equilibrium time between adsorbent and adsorbate for the solutions contaminated with metals is about 40 minutes. The Langmuir model adjusted to most results, indicating monolayers adsorption of Cd(II), Pb(II), and Cr(III). The values obtained for LangmuirQmshow a higher adsorption capacity caused by chemical modifications, with values such as 19.54 mg Cd(II) per g of M. NaOH, 42.46 mg of Pb(II) per g of M. NaOH, and 43.97 mg of Cr(III) per g of M H₂O₂. Results showed that modified cassava peels are excellent adsorbent, renewable, high availability, and low-cost materials and a feasible alternative in the removal of metals in industries.

In this study, different soil Pb concentrations [24 (control), 80, 136, 362, and 1150 mg kg⁻¹] were used to analyze the tolerance threshold and accumulation potential of Brassica juncea L. in a pot experiment under greenhouse conditions. In addition to growth and Pb accumulation, the following contamination indices were calculated: transfer coefficient (TC), translocation factor (TF), and tolerance index (TI). Growth and Pb accumulation were determined at 60 days after emergence. The Pb concentrations were determined using the flame atomic absorption spectrometry (FAAS). The plant height was affected by soil Pb contamination, and it decreased from 1.37 to 0.83 m when the soil Pb concentration increased from 24 (control) to 1150 mg kg⁻¹, respectively. The Pb concentration in the shoots and roots increased as the Pb concentration in the soil increased, reaching 94 mg kg⁻¹ in shoots and 783 mg kg⁻¹ in roots when was grown under 1150 mg kg⁻¹ of Pb. TF was <1 at all levels of contamination. The TI values suggested that B. juncea presented Pb tolerance in Pb contaminated soils. Our findings indicate that B. juncea has the potential to accumulate Pb in soil under tropical conditions.

Authors: Affonso Celso Gonçalves Jr., Herbert Nacke, Daniel Schwantes and Gustavo Ferreira Coelho