Abstract
The removal of water pollutants has been widely addressed for the conservation of the environment, and novel materials are being developed as adsorbent to address this issue. In this work, different residual biomasses were employed to prepare biosorbents applied to lead (Pb(II)) ion uptake. The choice of cassava peels (CP), banana peels (BP), yam peels (YP), and oil palm bagasse (OPB) was made due to the availability of such biomasses in the Department of Bolivar (Colombia), derived from agro-industrial activities. The materials were characterized by ultimate and proximate analysis, Fourier Transform Infrared Spectroscopy (FTIR), Brunauer-Emmett-Teller analysis (BET), Scanning Electron Microscopy (SEM), and Energy Dispersive X-Ray Spectroscopy (EDS) in order to determine the physicochemical properties of bioadsorbents. The adsorption tests were carried out in batch mode, keeping the initial metal concentration at 100 ppm, temperature at 30 °C, particle size at 1 mm, and solution pH at 6. The experimental results were adjusted to kinetic and isotherm models to determine the adsorption mechanism. The remaining concentration of Pb(II) in solution was measured by atomic absorption at 217 nm. The functional groups identified in FTIR spectra are characteristic of lignocellulosic materials. A high surface area was found for all biomaterials with the exception of yam peels. A low pore volume and size, related to the mesoporous structure of these materials, make these bioadsorbents a suitable alternative for liquid phase adsorption, since they facilitate the diffusion of Pb(II) ions onto the adsorbent structure. Both FTIR and EDS techniques confirmed ion precipitation onto adsorbent materials after the adsorption process. The adsorption tests reported efficiency values above 80% for YP, BP, and CP, indicating a good uptake of Pb(II) ions from aqueous solution. The results reported that Freundlich isotherm and pseudo-second order best fit experimental data, suggesting that the adsorption process is governed by chemical reactions and multilayer uptake. The future prospective of this work lies in the identification of alternatives to reuse Pb(II)-contaminated biomasses after heavy metal adsorption, such as material immobilization.
Highlights
The contamination of aquatic ecosystems has been associated with increasing anthropogenic activities that discharge untreated wastewater into the environment [1]
The adsorption process is a complex phenomenon involving many steps; many factors affect the removal yield of heavy metals from aqueous solutions
The yam peels (YP), cassava peels (CP), and banana peels (BP) biomasses reported the highest removal yields for Pb(II) ion uptake, which can be attributed to the high surface area and small pore size increasing the adsorption properties of such materials; this is consistent with the results reported in Figure 5, corresponding to the Energy Dispersive X-Ray Spectroscopy (EDS)
Summary
The contamination of aquatic ecosystems has been associated with increasing anthropogenic activities that discharge untreated wastewater into the environment [1]. The changes in water chemistry owning pollution issues have serious effects on living organisms, especially aquatic biota directly, and human beings indirectly [2,3]. Sci. 2019, 9, 4486 pollutants which may affect the public health; heavy metals pollutants are especially considered a serious environmental issue affecting soil, ecosystems, and surface water [4]. Lead is one of the most significant environmental pollutants, due to its effects on health, causing damage to the central nervous system, gastrointestinal diseases, headaches, dizziness, diarrhea, and vomiting [5]. According to the World Health Organization, the maximum concentration of lead allowed in drinking water is 0.01 mg/L [7]. To reach lower concentrations than the limit, it is necessary to apply treatment methods such as adsorption, ion exchange, coagulation, and chemical precipitation, among others
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