Abstract
With the intensive industrial activity worldwide, water pollution by heavy metal ions (HMIs) has become a serious issue that requires strict and careful monitoring, as they are extremely toxic and can cause serious hazards to the environment and human health. Thus, the effective and efficient removal of HMIs still remains a challenge that needs to be solved. In this context, copper(II), cobalt(II) and iron(III) sorption by chitosan (CS)-based composite sponges was systematically investigated in binary and ternary systems. The composites sponges, formed into beads, consisting of ethylenediaminetetraacetic acid (EDTA)- or diethylenetriaminepentaacetic acid (DTPA)-functionalized CS, entrapping a natural zeolite (Z), were prepared through an ice-segregation technique. The HMI sorption performance of these cryogenically structured composite materials was assessed through batch experiments. The HMI sorption capacities of CSZ-EDTA and CSZ-DTPA composite sponges were compared to those of unmodified sorbents. The Fe(III) ions were mainly taken up when they were in two-component mixtures with Co(II) ions at pH 4, whereas Cu(II) ions were preferred when they were in two-component mixtures with Co(II) ions at pH 6. The recycling studies indicated almost unchanged removal efficiency for all CS-based composite sorbents even after the fifth cycle of sorption/desorption, supporting their remarkable chemical stability and recommending them for the treatment of HMI-containing wastewaters.
Highlights
Heavy metal ions (HMIs) occur naturally in the earth’s crust
It is known that chelating agents such as aminopolycarboxylic acids form stable structures with HMIs
All CS-based composite sorbents obtained through the ice-segregation approach exhibited a porous structure with walls arranged along the freezing direction (Figure 1B), which could allow easy and rapid access of HMIs towards ligand moieties
Summary
Heavy metal ions (HMIs) occur naturally in the earth’s crust. HMIs can enter into our bodies through food, drinking water and air. Some HMIs (e.g., copper, zinc, iron) are vital in maintaining the metabolism of the human body when they are present in small amounts. At high concentrations, they are extremely toxic for living organisms or other biological systems [1]. The major sources of water pollution by HMIs are geological (natural) sources, mining and metal processing and industrial and domestic use of HMI salts (e.g., chromium in tanneries, copper and arsenic salts in pesticides or lead in petroleum products). HMIs cannot be degraded and the only way to prevent their release into the environment is to recover and reuse them
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