Palygorskite/iron nanoparticles composite for the removal of in(III) from aqueous solutions: Characterization, performance, and mechanism

Abstract

Although indium and related derivatives are essential to the semiconductor communication sector, they are rather hazardous to the environment. A thermal-acid modified palygorskite supported nano-zero-valent iron composite (HA-PAL/nZVI) suitable for In(III) adsorption was prepared by a simple and rapid liquid-phase reduction method, and HA-PAL/nZVI was characterized by XRD, FT-IR, BET and SEM-EDS. The experimental results show that the saturated adsorption capacity of HA-PAL/nZVI for In(III) can reach 301.76 mg·g⁻¹ within 360 min under pH 3 and K 298.15. The adsorption process of In(III) conforms to the Langmuir isotherm model and the pseudo-second-order kinetic model, and ΔH = 10.04 kJ·mol⁻¹, ΔS = 90.80 J·mol⁻¹·K⁻¹, ΔG < 0, which belongs to the rate-controlling step, spontaneous and endothermic chemical adsorption; In addition to Cu²⁺ and PO₄³⁻, cations (Na⁺, K⁺, Ca²⁺, Mg²⁺, Sn⁴⁺, Pb²⁺, Zn²⁺, Cd²⁺), anions (Cl⁻, SO₄²⁻, NO₃⁻, CO₃⁻), organic molecules (H₂C₂O₄) and ionic strength showed significant tolerance to the adsorption of In(III) by HA-PAL/nZVI. Combined with XPS analysis results, it was determined that the HA-PAL/nZVI adsorption mechanism of In(III) was mainly based on redox, co-precipitation and physical adsorption.