Abstract
Due to the extreme rise of sludge pollution with heavy metals (e.g. copper), the options for its disposal or treatment are decreasing. On the contrary, properly heavy metal-cleaned sludge can be used as an alternative sustainable energy and agriculture source. The aim of this study was to develop a novel nanoadsorbent, based on irreversibly linked amino-rich polymer onto previously silica-coated magnetic nanoparticles (MNPs) that can be applied efficiently for metal removal. MNPs were coated uniformly by 3 nm thick silica layer (core-shell structure), and were additionally modified with systematic covalent attachment of derived branched polyethyleneimine (bPEI). The formed structure of synthesized MNPs composite was confirmed with several analytical techniques. Importantly, nanoadsorbents exhibit high density of chelating amino groups and large magnetic force for easier separation. The importance of introduced bPEI, effect of pH, initial heavy metal concentration onto copper uptake efficiency and, further, nanoadsorbent regeneration, were studied and explained in detail. The adsorption isotherm was well fitted with Langmuir model, and the maximum adsorption capacity was shown to be 143 mg·g−1 for Cu2+. The reusability and superior properties of silica-coated MNPs functionalized with derived-bPEI for copper adsorption underlie its potential for the removal application from heavy metals contaminated sludge
Highlights
During recent decades, the upgrade of municipal wastewater treatment plants has led to increased sludge production
The results revealed superior magnetic nanoparticles (MNPs)@SiO2@GOPTS-branched polyethyleneimine (bPEI) ability for Cu2+ removal due to the high density of amino groups
The results revealed that the MNPs crystal structure was assigned to maghemite (Figure 1), as diffraction peaks corresponded to a standard reference card (JCPDS 72-0246, cubic space group Fd-3m), typical for a maghemite cubic spinel crystal structure
Summary
The upgrade of municipal wastewater treatment plants has led to increased sludge production. Moderately HM-cleaned sewage sludge can be used beneficially on lands as a fertilizer or as a soil conditioner, which can be advantageous by providing an economical, renewable disposal alternative, together with the additional nutritious supplement for plants [1,2,3,4,5]. Despite the known necessity of the latter as an indispensable element for plants and humans, an excessive amount of copper can result in severe health problems [7]. Following this issue, there is an urgent need to remove the excess copper from sewage sludge to provide recycling (zero waste concept) and economical disposal of sludge with high nutrients values (i.e., phosphorus, nitrogen, organic matter) for agricultural land applications
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