Abstract
Usages of hospital sludge as a biochar adsorbent for wastewater treatment plants were investigated. Microwave carbonization was used to carbonize the sludge and then chemically activated with ZnCl2 to increase surface area and porosity. A newly designed amine functional group’s doped Sludge Biochar Carbon (SBC) presents effective inorganic arsenic (As (III)) and organic arsenic (Dimethylarsinic Acid, DMA) adsorption in water. The pore volume, pore size distribution and specific surface area were determined by performing nitrogen adsorption-desorption measurements. The Fourier Transform Infrared of the SBC was recorded to study the functional groups at room temperature. The composition of SBC was further determined by X-ray Photoelectron Spectroscopy. In order to understand the effect of amine functional complexes on arsenic adsorption, the adsorption mechanism of As (III) and DMA on SBC surfaces modified with amine functional complexes was studied using Density Functional Theory (DFT). DFT results showed that both physical and chemical adsorption of As (III) and DMA on SBC surfaces occurred. The participation of amine functional complexes greatly promoted the surface activity of SBC surface and its adsorption capacity on arsenic. The physical adsorption energies of As (III) and DMA on SBC surface with amine functional complexes were − 38.8 and − 32.4 kJ mol− 1, respectively. The chemical adsorption energies of As (III) and DMA on SBC surface with amine functional complexes were − 92.9 and − 98.5 kJ mol− 1, respectively.
Highlights
Biochar has been identified as an effective adsorbent that can be used to remove various heavy metals dissolved in water, because the specific surface area and microporous structures of biochar are high
This study investigated the effect of carbonization at different temperature on biochar carbon
The results showed that Sludge Biochar Carbon (SBC) has a uniform pore at 500 °C, as shown in Fig. 1c, but the SBC did not have any pores at 300 and 400 °C, as shown in Fig. 1a and Fig. 1b
Summary
Biochar has been identified as an effective adsorbent that can be used to remove various heavy metals dissolved in water, because the specific surface area and microporous structures of biochar are high. It hosts several surface functional groups, such as carboxyl (−COOH), hydroxyl (−OH) and amino (−NH2), for adsorbing heavy metal effectively [1, 2]. These groups can work through electron donation, cation exchange, electrostatic attraction, or surface complexation to effectively remove heavy metals [3]. As (III) is more toxic than As(V) since the former binds to single but with higher affinity for groups of sulfhydryls that associate with a variety of proteins and inhibit their activity and given its electronic structure, As (III) is more stable than As(V) [11]
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