The usefulness of untreated powdered eggshell as low-cost adsorbent for the removal of pentachlorophenol (PCP) from aqueous solutions was investigated. The most important parameters affecting the adsorption process, including the pH and ionic strength, were examined. The adsorption characteristics of PCP onto eggshell were evaluated in terms of kinetic and equilibrium parameters. The kinetic data were studied in terms of the pseudo-first order, pseudo-second order and intra-particle diffusion kinetic models. The equilibrium data were analyzed using the Langmuir, Freundlich, Sips and Redlich-Peterson isotherm models. The pseudo-second order model best described the adsorption kinetics. Using the Langmuir equation, the monolayer adsorption capacity of eggshell for PCP was found to be 0.127 mg/g. The results showed that PCP can be effectively removed from aqueous solution employing eggshell as a cheap adsorbent.
A new composite adsorbent was prepared by modifying low cost local adsorbent (LCL) using MgFe layered double hydroxide (LDH). This low cost local adsorbent was also prepared from the activation of date palm leaf derived from agricultural waste. In comparison to the low LCL, the adsorption capacity of the new composite adsorbent (LCL/MgFe-LDH) was improved. This was measured in terms of its ability to remove lead from wastewater. The Scanning electron microscope (SEM), Energy dispersive spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR) and the specific surface area by the (Brunauer, Emmett and Teller) theory (BET) tests were conducted for the characterisation of LCL and LCL/MgFe-LDH. The behaviour of the lead adsorption processes by using LCL/MgFe-LDH as adsorbent was investigated in batch experiments by examining different values of solution pH, contact time, adsorbent dose and initial Pb2+ concentration. High removal efficiency was exhibited by LCL/MgFe-LDH, a value almost double that of LCL. This was attributed to the increase in surface area of LCL/MgFe-LDH (79.7 m2·g–1) in contrast to the surface area of LCL (24.5 m2·g–1). The Freundlich equations and pseudo-second-order kinetics model were appropriate for the provision of adsorption equilibrium data for Pb2+ on adsorbents. These results reveal the great potential of the new composite adsorbent (LCL/MgFe-LDH) if applied to the absorption of heavy metal ions.
Arsenic is one of the most harmful pollutants in groundwater. In this paper, the Nepali bio sand filter (BSF) was modi-fied with different bio-adsorbents, and proved to be an efficient method for arsenic removal from groundwater. Three dif-ferent bio-adsorbents were used to modify the Nepali BSF. Iron nails and biochar BSF, ~96% and ~93% arsenic removal was achieved, within the range of WHO guidelines. In iron nails, BSF and biochar BSF ~15 dm3∙h–1 arsenic content water was treated. In the other two BSFs, rice-husk and banana peel were used, the arsenic removal efficiency was ~83% of both BSFs. Furthermore, the efficiency of rice-husk and banana peel BSFs can be increased by increasing the surface area of the adsorbent or by reducing the flow rate.