International Research Journal of Environment Sciences________________________________ ISSN 2319–1414Vol. 3(1), 23-30, January (2014) Int. Res. J. Environment Sci. International Science Congress Association 23 Study for the treatment of Cyanide bearing Wastewater using Bioadsorbent Prunus Amygdalus (Almond shell): Effect of pH, adsorbent dose, Contact Time, Temperature, and initial Cyanide concentration Naveen Dwivedi1*, Chandrajit Balomajumder and Prasenjit Mondal2 Uttarakhand Technical University, Dehradun, UK-248007 Department of Biotechnology, S.D. College of Engineering and Technology, Muzaffarnagar-251001, UP, INDIA Department of Chemical Engineering, Indian Institute of Technology Roorkee, Roorkee-247667, UK, INDIAAvailable online at: www.isca.in, www.isca.me Received 17th December 2013, revised 11th January 2014, accepted 20th January 2014 AbstractIn the present study, the bio-removal of cyanide ions from aqueous solution by Prunus amygdalus (Almond Shell) granule has been investigated as a function of equilibrium pH, bio adsorbent dose, contact time, temperature and initial cyanide concentration. Batch study revealed that the bio-adsorption of cyanide on Prunus amygdalus (Almond Shell) granule was strongly pH dependent, and maximum cyanide removal was found to occur at equilibrium pH of 7. Optimum adsorbent dose, contact time, and temperature were found 20g/L, 90 minutes, and 30C respectively. Initial cyanide concentration was also investigated as a function of cyanide removal efficiency of bioadsorbent. Keywords: Cyanide, wastewater bioadsorbent, prunus amygdalus.Introduction Cyanide is one of the toxic chemical found in wastewater discharges of the electroplating, metal finishing, steel tempering, mining (extraction of metals such as gold and silver), automobile parts manufacturing, photography, pharmaceuticals and coal processing units1-3. Cyanide is included in the CERCLA priority list of hazardous substances and it occupies 28th position in the list of most hazardous chemicals. Different forms of cyanide have awful health effects on people as well as other living organisms. Therefore the permissible limit of cyanide in the surface water according to Indian standard has set a minimal national standard (MINAS) limit for cyanide in effluent as 0.2 mg/L. USEPA (US Environmental Protection Agency) standard for drinking and aquatic-biota waters regarding total cyanide are 200 and 50 ppb respectively8,9. Therefore, environmental regulations require reducing the cyanide concentration in wastewater to below 0.2 mg/L prior to discharge into the environment. All forms of cyanide can be toxic at high levels, but the more toxin form of cyanide is hydrogen cyanide. Therefore, cyanide and metal cyanide complexes in industrial waste water must be treated or reduced to lowest levels before being discharged. Several treatment processes such as physical, chemical and biological oxidation have been exploited for the reduction of cyanide levels in waste solutions/ slurries in compliance with environmental regulations 10. Biological process is generally the preferred technique for treating wastewater owing to its cost-effectiveness and environmental easiness, there is little work on the use of bioprocesses for treatment of cyanide-laden wastewater11-13. Another conventional method for cyanide removal is Chemical process14. It is uninvited technique because it requires the various chemical and regents and secondary pollutants are created furthermore it also needs some additional treatment prior to its disposal. Chemical processes of cyanide removal are not appropriate for environmental and economic perspectives15. Adsorption is a simple and attractive method for the removal of toxic compounds from the effluents due to its high efficiency, easy handling and economic feasibility. Adsorption systems are not affected by the toxicity of the target compound(s) and do not require hazardous chemicals. Moreover, adsorption facilitates concentrating and then recovering the adsorbed compounds if desired16. Biosorption of cyanide from aqueous solutions is quite a new process that has confirmed very promising in the removal of contaminants from aqueous effluents. Various agro based adsorbents have been reported for cyanide removal from water and wastewater due to their abundant availability and low cost16. However, industrial wastewater mainly from electroplating and mining industries normally contains higher cyanide concentration such as 5-250 mg/ l and there is very few literature on the removal of cyanide from water containing cyanide at higher concentration. For making adsorption process more feasible and cost effective, there is urgent need of low cost adsorbents with higher adsorption capacities. Further, almond shell has hardly been investigated for cyanide removal from water. Therefore, in this work the potential of Prunus amygdalus (Almond Shell) granule, an agro- based biomass for the removal of cyanide from water has been explored. Experimental studies on cyanide removal have been done in batch reactor configuration. The effects of solution pH, bio-adsorbent dose, contact time, temperature and initial cyanide concentrations on the removal of cyanide have been studied. International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(1), 23-30, January (2014) Int. Res. J. Environment Sci. International Science Congress Association 24 Material and Methods The raw material used was almond shell (Prunus Amygdalus), which were obtained from the local market of Muzaffarnagar, UP, India. The shells were cut into small pieces and, after drying and crushing, washed thoroughly with double-distilled water to remove adhering dirt. Then, they were dried in oven at 100°C for 24 h and were sieved 17. After screen analysis of the grinded product the fraction having average particle size of ~ 600΅m was used. A 1-L stock solution of cyanide was prepared by dissolving 1.885 g NaCN in distilled water with NaOH pellet. All chemicals used were analytical grade and purchased from Merck Co and Qualigens Fine Chemical Company (Glaxo Smithkline). Characterization of bio adsorbent: The BET (Brunauer-Emmett-Teller) method was extensively used for measuring the surface area and pore volume. It is essential for understanding the potential of an adsorbent in the adsorption process. Ultimate analysis and physical properties of the untreated almond shell are shown in table 1. Procedure: Batch experiments were carried out in a 250 ml conical flask at 30C in an incubator shaker at 125 rpm using 100 ml of cyanide solution of known concentration and adsorbent doses. The solutions pH were maintained by measuring it intermittently each hour and controlled by drop wise addition of N/10 HCL or NaOH solutions. Ranges of operating parameters for various experiments are shown in table 2. All experiments were performed in triplicate and the results average was reported. In each case sample was filtered through a 0.45 ΅m membrane filter. Filtrate was analyzed for total cyanide ion concentration using picric acid method. The cyanide adsorption efficiency was calculated as using following formula: (C) Χ 100 % Removal = Ci Where, and are the initial and residual concentration at equilibrium (mg/L) respectively of cyanide in solution. Analytical measurements: Analysis of cyanide was done by using picric acid methods 18 at 520 nm wavelength using double beam UV/visible spectrophotometer (Microprocessor UV/VIS EI Spectrophotometer model 1371). Free cyanide and weak acid cyanide reacts with the picric acid reagent to produce an orange color that can be measured colorimetrically at a wavelength of 520 nm. The dissolved alkali metal picrate was converted by cyanide to the colored salt of iso-purpuric acid and its concentration was measured. Table-1 Physical properties and ultimate analysis of the untreated almond shell Elemental analysis of almond shell Physical properties of almond shell C H N S M (%) Ash (%) VM (%) FC (%) BET surface area (m/g) Total pore volume (m/g) 50.56.60.210.0064.91.1079.514.549.56940.0250 VM: Volatile matter, FC: Fixed carbon Table-2 Ranges of operating parameters for pH, adsorbent dose, contact time, temperature and Initial cyanide concentrationObjective of experiment Operating parameters To study the effect of pH on cyanide removal AD: 20 g/L; ICC: 100 mg/l; Temp.: 30 0 C; Contact time: 90 min; pH: 2-12 To study the effect of adsorbent dose on cyanide removal ICC: 100 mg/l; Temp.: 30 0 C; time: 90 min; solution pH 7; AD: 5, 10, 15, 20, 25, 30, 40 g/L. To study the effect of contact time on cyanide removal AD: 20 g/L, ICC: 100 mg/l; Temp.: 30 0 C; solution pH 7; time: 15, 30, 45, 60, 75, 90, 105, 120 min; To study the effect of temperature on cyanide removal AD: 20 g/L; ICC: 100 mg/l; Time.: 90 min; solution pH:7; Temp: 20, 25, 30, 35, 40, 45C To study the effect of Initial cyanide concentration on cyanide removal AD: 20 g/L; Time.: 90 min; solution pH:7; Temp: 30 0 C; ICC: 100-800 mg/l; AD: Adsorbent dose, IFC: Initial cyanide concentration. International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(1), 23-30, January (2014) Int. Res. J. Environment Sci. International Science Congress Association 25 Results and Discussion The most extensively used technique for estimating surface area is the BET method19. BET surface area and total pore volume on the adsorbent were 49.5694 m/g and 0.0250 m/g, respectively. It depicts the almond has an extensive allocation of surface area and excellent pore volume. These properties make it a good adsorbent. From Field Emission SEM (FE SEM) micrographs of untreated almond shell adsorbents before and after adsorption as shown in Figure 1(a-b) it is evident that active sites of adsorbents are covered due to the adsorption of cyanide on it. (a) (b) Figure-1 Scanning Electron Micrograph of untreated almond shell (a) Untreated almond shell before adsorption, (b) Untreated almond shell after adsorptionRemoval of cyanide species by untreated Prunus amygdalus (Almond Shell) granule has been studied in the present investigation and the effects of various process parameters such as pH, adsorbent dose, contact time, temperature and initial cyanide concentration are discussed as follows: Effect of pH: An effect of solution pH on the removal of cyanide for adsorbent is shown in figure 2. From figure 2 it seems that pH played an important role for the removal of cyanide from aqueous solutions by adsorption. It alters the surface charge of the adsorbent. The effect of pH on the adsorption could be attributed to several mechanisms such as electrostatic interaction, complexation, ion exchange and surface charge on carbon20,21. The effect of initial pH on the adsorption equilibrium of cyanide has been shown in figure 2. At pH 4, percent removal of cyanide increases with the increase in solution pH. Significant improved in percentage removal of cyanide are observed within the pH range of 5-6. The highest cyanide removal of 91.5% obtained at pH 7 and then decreases considerably with the increase in solution pH up to 12. Based on the above observations it could be concluded that the surface charges on adsorbent and behavior of cyanide in water influence the % removal of cyanide. Effect of adsorbent dose: An effect of adsorbent dose on the removal of cyanide for adsorbent is shown in figure 3. From figure 3 it is evident that adsorption is mainly a surface phenomenon, the amount of surface vacant for adsorption and therefore the mass of adsorbent can extensively influence adsorption efficiency. Therefore, the effect of almond shell dosage on cyanide removal was investigated under the conditions given in table 2. As illustrated in figure 3, the increase in percentage removal of cyanide in the initial stage is due to the increase in adsorbent concentration. The removal of cyanide at a dose of 5 g/L was 35.6%; removal improved to 91.5% when the almond shell dosage was increased to 20 g/L and remained almost unchanged thereafter. The above observations can be explained by the fact that with the increase in adsorbent dose the number of active sites in unit volume of solution increases, which leads to an increase in the percentage removal of cyanide22. Bhumica et al. reported the removal of 20 mg/L cyanide given outcome 82% with the adsorbent dose of 40 g/L coal fly ash after 48 h contact time; and similarly H. Deveci et al. reported the removal of 100 mg/L cyanide given outcome 14.3, 35.4 and 92.3%, respectively with the adsorbent dose of 4.5 g/L plain, copper- and silver-impregnated GAC, after about 48 and 24 h contact time. The most conventional industrial adsorbent considering the low adsorption capacity of GAC (plain and modified) as well as its high production cost, coal fly ash has very little adsorption capacity on removal of cyanide ion at high concentration. The almond shell is certainly much more competent and cost effective and is therefore a proficient adsorbent for treating cyanide-laden wastewaters. International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(1), 23-30, January (2014) Int. Res. J. Environment Sci. International Science Congress Association 26 Figure-2 Effect of pH on the removal of cyanide by almond shell Process conditions: temp: 30 C, concentration of adsorbents: 20g/L, Contact time: 90 min; initial concentration of cyanide: 100 mg/l, rpm: 125) Figure-3 Effect of adsorbent dose on cyanide removal from water by almond shell, Process conditions: pH: 7; temp: 30 C; Contact time: 90 min; initial concentration of cyanide: 100 mg/l; rpm: 125.) Effect of contact time: The effect of contact time on adsorption was investigated under the conditions given in table 2. Figure 4 depicts at least 84.7% cyanide removal was achieved for concentrations as 100 mg/L cyanide a very short contact time of 15 min. Overall, the rate of cyanide removal was higher within 30-60 min contact time. The equilibrium removal efficiencies of cyanide were 91.5% at 90 min. This result implies high affinity and thus favourability of almond shell for adsorbing cyanide from industrial wastewaters. Effect of temperature: Cyanide removal at different temperature range, it was seen that equilibrium adsorption slightly increased and optimum temperature was established at 30C. Figure 5 depicts the temperature dependency of cyanide International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(1), 23-30, January (2014) Int. Res. J. Environment Sci. International Science Congress Association 27 removal. Adsorption processes are exothermic in nature; the extent and the rate of adsorption in most cases decrease with the increase in temperature23. At higher temperatures there is possibility of desorption of cyanide24,25. Effect of initial cyanide concentration: The influence of varying initial cyanide concentration from 100 to 800 mg/L on adsorption was investigated under the conditions given in table 2. Figure 6 depicts the results of influence of varying initial cyanide concentration on almond shell. Based on data plotted in figure 6, at least 91.5% cyanide removal was achieved for concentrations as lower as 100 mg/L cyanide and 63.6% cyanide removal was achieved for concentrations as high as 800 mg/L. The reduction of cyanide removal as an efficacy of its concentration can be explained by the restriction of available free sites for adsorption of cyanide with increased cyanide concentration in bulk solution for a fixed mass of adsorbent, as well as by the increase in intraparticle diffusion26. Figure-4 Effect of contact time (15-120 min.) on cyanide removal by almond shell Process conditions: pH: 7; temp: 30 C; Adsorbent dose: 20 g/L; initial concentration of cyanide: 100 mg/l; rpm: 125) Figure-5 Effect of temperature on cyanide removal by almond shell, (Process conditions: pH: 7; adsorbent dose: 20g/L; Contact time: 90 min; initial concentration of cyanide: 100 mg/l; rpm: 125.) International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(1), 23-30, January (2014) Int. Res. J. Environment Sci. International Science Congress Association 28 Comparison of present method with some latest literature on cyanide bio adsorption: The performance of the present bio-adsorbent is compared with some recently reported bio-adsorbents on cyanide removal from waste water as shown in table 3. From table 3 it seems that the adsorbents have been used under various conditions, therefore it is difficult to assess their performance preciously. However, the present adsorbent has been used at the highest concentration of cyanide with respect to other adsorbents and is competitive to other reported adsorbents. Figure-6 Effect of initial cyanide concentration (Process conditions: pH: 7; temp: 30 C; Contact time: 90 min; adsorbent dose 20 g/L; rpm: 125.) Table-3 Comparison of present method with some latest literature on cyanide bio-adsorption Adsorbent Cyanide compound pH Temp. C) Contact time (min) Dose (g/L) Initial CN concentration (mg/L) Cyanide removal (%) Reference Activated carbon NaCN 10 25 4320 1.5 102-532 - 27 GAC NaCN, ZnCN FeCN 6 25-35 60 36 60 5-50 20 5-50 50 100 200 85.6 80.1 70.2 28 Rice husk ash (RHA) NaCN 7-8 40 - 0.5 80 33.9 29 Raw/ heat activated Sepiolite [Cu(CN)2- - 20-22 - .05 100 40-90 30 Plain and Metal-impregnated GAC NaCN 10.5-11 - 22 0.2-4.5 100 1.5-14.3 (plain) 5.7-92.3 (AC-Ag) 4.4-35.4 (AC-Cu) 31 Sulfonated coal ZnCN 4.0 - 5 1.0 13 BDL* 32 Cu-II impregnated carbon KCN 10.5 - - - 500 99.56 33 Coal fly ash KCN 9 30 48 40 20 82 34 Almond shell NaCN 7 30 90 20 100 91.5 Present study *BDL: Below detection Limit. International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 3(1), 23-30, January (2014) Int. Res. J. Environment Sci. International Science Congress Association 29 ConclusionFrom the above discussions the following conclusions are made. i. The optimum pH for the removal of cyanide by almond shell adsorbent is ~ 7. ii. The optimum adsorbent dose is 20 g/l for the removal of cyanide from water. iii. The optimum temperature for cyanide removal is ~ 30 0 C. iv. The removal efficiency of almond shell is 91.5% at 100 mg/L and 63.6% at 800 mg/L cyanide concentration. v. The present adsorbent is proven to be potentially high affinity with cyanide ions and low-cost adsorbent for the removal of cyanide from aqueous solution as high concentration of cyanide ions in a relatively short contact time. References 1.Monser L. and Adhoum N., Modified activated carbon for the removal of copper, zinc, chromium and cyanide from wastewater, Sep. Purif. 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