DOI: 10.14457/tu.the.2016.1466
title: Removal of lead from solution by using low cost adsorbents from Apiaceae family

description: Access to clean and safe drinking water is basic right of human. Water contamination by heavy metals such as lead, arsenic, mercury, aluminum, zinc, chromium and iron is a major environmental problem due to their acute toxicity and their accumulation in food chains. One of such toxic heavy metals is lead, which can occur naturally or manufacture from industries such as storage batteries, radiators and solder for joints. World Health Organization (WHO) suggests that the tolerance limit of lead concentration in drinking water is 0.01 mg/l and not over than 0.05 mg/l by Thailand Pollution Control Department (PCD) and the limit of discharge wastewater for lead in Thailand is 0.2 mg/l. Therefore, this research work has been carried out on the feasibility of three low cost adsorbents for the removal of lead from contaminated water. This thesis organized results of the laboratory based studies on lead removal in synthetic water. Plants from Apiaceae family namely parsley, coriander and culantro were selected as low cost adsorbents for the lead adsorptions experiments, and their efficiency was compared with the other studies.         Physical and chemical characterization of selected adsorbents were carried out by Brunauer–Emmett–Teller (BET) in order to define the BET surface area, pore volume and average pore size, scanning electron microscope (SEM) for exploring the surface morphological and shape of external cell wall, Fourier Transform Infrared (FTIR) for surface functional groups analysis and Cation Exchange Capacity (CEC) for determine the number of exchangeable cations that adsorbents are capable of holding.        The influence of various parameters like adsorbent dose, pH, agitation speed, contact time and initial lead concentration was investigated by a series of batch experiments at 25 ± 3 °C. The percentage removal of lead was found to increase with the increasing dose of adsorbents, agitation speed and time for 10 mg/l initial Pb (II) concentration, whereas the percentage removal of lead was found to decrease with the increase in pH value greater than 4 and lead concentration. Although, it seems that all of parameters affected to the adsorption process, the noticeable parameters are dosage, pH and initial lead concentration. Contact time and agitation speed did not influence much. The maximum lead uptake was found to be 96.61%, 95.95% and 96.55% by parsley, coriander and culantro, respectively.          The equilibrium adsorption data after the experiments were designed with appropriate isotherms and kinetic models. The equilibrium data were well described for parsley and coriander by the Langmuir isotherm model, suggesting that the adsorption of Pb(II) onto these adsorbents is a mono-layer process and the adsorption behavior is homogeneous rather than heterogeneous for culantro data fitted well to Freundlich isotherm model indicating heterogeneous in the system. Kinetics data were best fitted by the pseudo second-order model for all of selected adsorbents, indicating that the adsorption process is chemisorption.          Moreover, the tea bags were used in the final stage of the experiment. It was found that at neutral of pH and without centrifuge under various contact time with 1 mg/l lead initial concentrations, the lead removal efficiency was found greater than 85% for 12 hrs. contact time and at this suitable time, it found that concentration of lead remaining in synthetic wastewater reached Thailand’s wastewater quality standard. Therefore, three selected adsorbents from Apiaceae family can be used as low cost adsorbents with high efficiency for removing lead at low concentration from wastewater because it can prepare without chemical and physical treatments.