Comparative Analysis of Nickel Adsorption by Natural Sisal Fiber and Treated with Citric Acid

Introduction: Removing nickel from wastewater is complex and costly, requiring research into alternatives with technical and economic solutions. An alternative would be the use of plant biomass. In the Northeast region of Brazil, one of these alternatives, with a large cultivation area, is sisal (Agave Sisaliana), which may have greater yields for this purpose through surface chemical treatment with citric acid, which inserts carboxylic groups into the structure of the plant fiber. Thus, the objective was to analyze the ability to remove nickel in solution by sisal fibers.

Methodology: For this purpose, part of the sisal fibers was cut into 0.5 cm, washed and dried; initially treated with NaOH (0.1 mol/L); washed with distilled water and treated with citric acid (1.2 mol/L). The fibers were identified by FTIR; XRD; XRF and SEM. Adsorption tests were carried out with nickel solution for the parameters: kinetics, balance, influence of pH and adsorbent mass.

Results: The XRF analysis demonstrated a greater presence of NiO adhered to the treated fiber (55.74%); FTIR confirmed the presence of non-ionized carbonyl in the region from 1700 to 1750 cm-1; the adsorption kinetic test demonstrated greater effectiveness of the treated fiber > 80%; an ideal adsorbent mass was observed to be 0.1g; the ideal pH for removal was 5.0 while the equilibrium test has the best Languimuir isotherm, the uncontrolled fiber obtained R2 = 0.9810 and the controlled fiber R2 = 0.9643.

Conclusion: Therefore, it was observed that the treatment of sisal fiber with citric acid increases the removal efficiency of nickel ion in aqueous solution, presenting itself as a low-cost and widely available material.