Efficacy Study of Low Cost Bioadsorbents in the Removal of Target Heavy Metals
Abstract
The purpose of this study is to investigate the effectiveness of rice husk, saw dust and tea waste as adsorbent for the removal of cadmium, chromium and lead ions respectively. The main parameters that influenced heavy metal adsorption on bioadsorbent were adsorbent dosage, % removal and pH value. Using the initial concentrations of lead, cadmium and chromium solutions at 10 ppm, the analysis was continued using contact time 60 mins. Besides that the influences of adsorbent dosage also been studied in a range of 10mg to 30mg.After that contains of heavy metal ions were analyzed using Atomic Adsorption Spectrophotometre (AAS). The maximum % removal of cadmium is 95.7% at 20ppm of initial concentration and 20mg adsorbent dosage of rice husk at pH 6.The maximum % removal of chromium is 98.75% at 20ppm of initial concentration and 10mg adsorbent dosage of sawdust at pH 3.The maximum % removal of lead is 99.25% at 20ppm of initial concentration and 10mg adsorbent dosage of tea waste at pH 5.5 batches. The batch studies revealed that the adsorption was influenced by the initial metal concentration, the biomass dose and solution pH. Langmuir isotherm model (R 2 ≈1) was used to analyze the equilibrium data.
Keywords
Download Options
Introduction
The increasing concern about the contamination of water bodies by heavy metals has stimulated a large number of researches to find possible ways to remove these toxic substances from the environment. To overcome some of the limitations of physicochemical treatments, there is a need for inexpensive and efficient technology for the treatment of metal containing wastes so that metal concentration can be reduced to environmentally acceptable levels. Use of biomass for metal removal/recovery is considered to be a viable alternative to conventional methods.
Various methods such as chemical precipitation, membrane process, ion exchange, solvent extraction, electrodialysis, and reverse osmosis are adopted for removing heavy metal ions. Which are economically non viable (Demirbas, 2008 ) and have many disadvantages such as incomplete metal removal, high reagent and energy consumption, and generation of toxic sludge or other waste products that require disposal or treatment (Dada et al. 2013). Biosorption technique has advantages over the conventional methods, which include reusability of biomaterial, low operating cost, selectivity for specific metal, short operation time and no chemical sludge. Having functional groups including carboxyl, hydroxyl, imidazole, sulphydryl, amino, phosphate, sulfate, thioether, phenol, carbonyl and amide etc the bioadsorbents form metal complexes or chelates with the heavy metal ions. (Amin et al, 2006) In the recent years agricultural based biosorbent materials have been utilized for removal of heavy metal through biosorption technique. coconut husk and shell, sea weeds, bagasse ash, hazelnut shell, peanut hull, tree fern, black gram husk, maize leaf, maize, sun flower waste, coffee beans, Ficus religiosa leaves, wheat bran, almond shell, tea waste are used as low cost biosorption material (Qaiser, et al., 2009).with the following background the present investigation was aimed to evaluate the adsorption efficiency of selected low cost bioadsorbents tea waste, rice husk and saw dust in the removal of lead, cadmium and chromium respectively.
Conclusion
In present work attempt have been made for studying the removal of heavy metals like cadmium, chromium and lead by low cost adsorbent like rice husk, saw dust and tea waste respectively. The major findings of the study are discussed in this section.
Batch studies on cadmium, chromium and lead removal showed significant effects of the variables adsorbent dose, initial metal concentration, pH. The results provide a good indication of the different operating conditions that would be required for efficient removal of each heavy metal from aqueous solution. Adsorbent dose is a significant factor in adsorbtion process since the percentage removal of heavy metals varies at different adsorbent dosage. When 10 ppm of initial heavy metal concentration is taken into consideration the optimum adsorbent dose was found to be 30mg in both the cases which shows optimum removal percentage of 92 % and 90.6 % in case of Cd and Cr respectively. While in case of lead initial adsorbent dose of 10 mg of tea waste shows optimum adsorption of 97.5 %. When 20 ppm of initial heavy metal concentration is taken into consideration the optimum adsorbent dose was found to be 10mg in both the cases which shows optimum removal percentage of 98.25 % and 99.25 % in case of Cr and Pb respectively. While in case of Cd adsorbent dose of 20 mg of rice husk shows optimum adsorption of 95.7 %. When 30 ppm of initial heavy metal concentration is taken into consideration the optimum adsorbent dose was found to be 10mg in both the cases which shows optimum removal percentage of 93.6 % and 92.86 % in case of Cd and Cr respectively. While in case of Pb adsorbent dose of 30 mg of tea waste shows optimum adsorption of 99.36%. pH is also a significant factor in adsorbtion process since it causes electrostatic changes in the solution. At pH 6 of rice husk shows maximum adsorption efficiency for cadmium is 95.7%, for chromium at pH 3 of saw dust shows maximum adsorption efficiency 98.75% and for lead at pH 5.5 of tea waste shows maximum adsorption efficiency 99.25. Langmuir isotherm were observed to fit the equilibrium data and the model parameters were calculated using linearized equations. Langmuir isotherm model R 2 ~ 1 is in good agreement with the experimental data. These experimental results revealed that Rice husk can be used as an efficient bioadsorbent for the removal of Cd, Saw dust can be used as an efficient bioadsorbent for the removal of Cr and Tea leaves can be used as an efficient bioadsorbent for the removal of Pb