Using Cilantro Leaves and Stems to Remove Lead, Cadmium and Turbidity from Contaminated Water
Njue, Martin Kivuti
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Water as a resource in Kenya is increasingly being polluted as its population increases. Ingestion of heavy metal compounds poses great risks to human health since heavy metal ions can accumulate their amounts along the food chain. Therefore, it is necessary to remove or minimize the heavy metal ions in contaminated water. A number of methods are already in operation such as ion-exchange, chemical coagulation, electrochemical methods, membrane process, using natural zeolite, ultra-filtration; with most of them generating toxic sludge. The necessity to explore simple methods of wastewater treatment that can be economically viable and environmentally friendly motivated the current research work. In this study, cilantro (Coriandrum sativum) was used as an adsorbent with previous studies showing that it is a promise in removal of metal ions. This study investigated adsorption capacity and efficiency of fresh and dry cilantro leaves and stems in removal of Pb2+, Cd2+ ions and turbidity from simulated contaminated water. Cilantro fresh leaves and fresh stems were grounded to obtain the wet adsorbents while for the dry adsorbents, fresh cilantro leaves and stems were sun dried at room temperature until their dry masses remained constant and grounded to fine powder. Batch sorption studies were carried out while varying parameters of contact time, shaking speed, temperature, adsorbent dose, pH and concentration of metal ions in solution. For all the batch studies, 100 mg/L working solution of Pb2+ and Cd2+ ions was used, shaking speed of 6 revolutions per second, pH of 6 and temperature of 25oC. The optimum contact time for adsorption of Pb2+ ions was 1½ hours and 2 hours for Cd2+ ions adsorption. Residue Pb2+ and Cd2+ ions concentrations were determined using atomic adsorption spectroscopy. The adsorption of Cd2+ ions was described by Langmuir isotherm with Qmax values of 250.00, 51.28, 4.68 and 15.06 mg/g for fresh leaves (FL), fresh stems (FS), dry leaves (DL) and dry stems (DS) biomasses respectively. Freundlich isotherms described adsorption for Pb2+ ions by FL, FS, DL and DS with Kf values of 45.87, 144.53, 1.40, and 2.14 mg/g respectively. The efficiency of DL to remove turbidity increased with increase in dosage with 24.9% of turbidity removed at a dosage of 0.2g while FS showed a decrease in percentage turbidity removal with increase in adsorbent dosage with an optimum percentage removal of 6.4% at 0.1g dosage. The results from this study suggest that fresh and dry cilantro leaves and stems are potential adsorbents of Cd2+, Pb2+ ions and turbidity.