AMMONIA ADSORPTION FROM AQUEOUS SOLUTION USING NATURAL ZEOLITES. Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 31490, Thailand

Transcription

1 AMMONIA ADSORPTION FROM AQUEOUS SOLUTION USING NATURAL ZEOLITES Paradorn Sopa, Pornpan Pungpo * Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 31490, Thailand * pornpan_ubu@yahoo.com Abstract: Two natural adsorbents, natural zeolites, clinoptilolite and offretite have been applied to adsorb ammonia from aqueous solution on laboratory scale by batch absorption experiment. The results show that natural zeolites Clinoptilolite is more higher adsorption efficiency to reduce significantly ammonia than natural zeolites Offretite with removal efficiency of 97.35% and 47.40%, respectively. Therefore, Clinoptilolite has been selected as a potential adsorbent for further study. The optimum condition for ammonia adsorption are obtained as following; the optimum ratio of the natural zeolite Clinoptilolite per aqueous solution 40 g/l and an hour for adsorption time by stirring 30 seconds every 30 minutes. The adsorption isotherm study of ammonia corresponds well to the Langmuir isotherm. Based on the obtained results, Clinoptilolite is a highly recommendable adsorbent for ammonia adsorption in wastewater treatment with economically and friendly environmental chemical process. Introduction : Nitrogen compounds are nutrients essential to all forms of life, but when present in substantial quantities in receiving water such as rivers, lakes can cause their eutrophication as well as in increased dissolved oxygen depletion and fish toxicity. High concentration of ammonia nitrogen is commonly present in industrial waste waters such as textile, landfill leachate and fertilizer wastewater. Therefore, the removal of nitrogen nutrients gains greater importance in wastewater treatment. Zeolite is a well-known material for its abilities to preferentially remove ammonium ions from wastewater.unlike systematic ion exchange resins, zeolite is known to possess a high selective ion-exchange capability for ammonium ion than Ca 2+ and Mg 2+. Natural zeolites, low cost ion-exchangers, were mainly used to remove ammonium ions from secondary effluent by selective ion exchange. The aims of this study were to apply two natural zeolites for ammonia adsorption. The effect of zeolites dosage, adsorption time and initial concentration on establish optimum conditions for ammonia adsorption were further investigated. In addition, equilibrium isotherms of the uptake of ammonium ion on zeolite were studied. Methodology : Zeolite adsorbents and other reagents The natural zeolites, Offretite and Clinoptilolite were used as a powder. An aqueous solution (30 ppm) of ammonia is prepared by dissolving analytical grade ammonium sulphate (NH 4 ) 2 SO 4 perfume in oven at o C for 1-2 hours into deionized water. Instrument Ultraviolet-visible spectroscopy (UV/Vis spectroscopy) LAMBDA 25, PerkinElmer, Massachusetts, USA. at 640 nm with single wave length was used for ammonia measurement. 37 th Congress on Science and Technology of Thailand 1

2 Preliminary adsorption study using two natural zeolites Each of weight two natural zeolites (1.0 g) was put into Erlenmeyer flasks with 25 ml of 30 ppm ammonia solution. All suspensions were performed batch adsorption for an hour. All solutions were kept in Nalgene bottle after filtration of all suspension through filter paper. Concentration of ammonia after batch adsorption was measured by UV/Vis spectroscopy at wavelength 640 nm with single wavelength. Investigation of optimum condition for ammonia adsorption by natural zeolites - Effect of zeolite amount on optimum ammonia adsorption A natural zeolite given the best result from preliminary ammonia adsorption was selected. The natural zeolite was accurately weighed and put into the Erlenmeyer flasks. The zeolite amount with 0.5, 1.0, 1.5 and 2.0 g were put in the 25 ml of 30 ppm ammonia solution was added into Erlenmeyer flasks. Then batch adsorption was performed by suspending all natural zeolites in ammonia solution for an hour. Systematic perturbation was performed by using magnetic stirrer at time of 30 minutes for 30 second. All solutions were kept in Nalgene bottle after filtration of all suspension through filter paper. Concentration of ammonia after batch adsorption was measured by UV/Vis spectroscopy at wavelength 640 nm with single wavelength. - Effect of adsorption time on optimum ammonia adsorption A natural zeolite were accurately weighed in the optimum amount and put into the Erlenmeyer flasks. 25 ml of 30 ppm ammonia solution was added into the Erlenmeyer flasks. Batch adsorption was performed by suspending all natural zeolites in ammonia solution. Effect of adsorption time was performed by suspending all natural zeolites in ammonia solution for 15 minutes, 30 minutes, 1 hour, 2 hours and 6 hours. Systematic perturbation was performed by using magnetic stirrer at time of 30 minutes for 30 second. All solutions were kept in Nalgene bottle after filtration of all suspension through filter paper. Concentration of ammonia after batch adsorption was measured by UV/Vis spectroscopy at wavelength 640 nm with single wavelength. - Effect of initial ammonia concentration on optimum ammonia adsorption Concentrations of ammonia solution are 5.00, 10.00, 20.00, 30.00, and ppm. A natural zeolite was accurately weighed in the optimum amount and put into the Erlenmeyer flasks. 25 ml of ammonia solution was added into the Erlenmeyer flasks. Batch adsorptions are performed by suspending natural zeolite in ammonia solution for an hour. Systematic perturbation was performed using magnetic stirrer at time of 30 minutes for 30 seconds. All solutions were kept in Nalgene bottle after filtration of all suspension through filter paper. Concentration of ammonia after batch adsorption was measured by UV/Vis spectroscopy at wavelength 640 nm with single wavelength. Investigation of adsorption isotherm - Freundlich isotherm for ammonia adsorption Freundlich isotherm for ammonia adsorption was obtained by plotting the value of log C e as X-axis against log C ads Y-axis over entire concentration range of ammonia. The Freundlich isotherm equation is following; Log C ads = 1/n log C e + log K Where; C e is the equilibrium concentration of ammonia in solution. C ads is the concentration of ammonia adsorbed onto zeolite. K is a parameter related to the temperature. N is a characteristic constant for the adsorption system under study. 37 th Congress on Science and Technology of Thailand 2

3 The Freundlich constants (n and K) were calculated from slop and intercept from linear equations. The obtained Freundlich constants (n and K) were compared with experimental results for preliminary adsorption for checking of the accuracy and consistency between them. R 2 of all linear equation were considered the reasonable of isotherm model. - Lanmgmuir isotherm for ammonia adsorption Langmuir isotherm for ammonia adsorption was obtained by plotting the value of C e as X-axis against C e /C ads as Y-axis over entire concentration range if ammonia. The Langmuir isotherm equation is as following; C e /C ads = C e /Q + 1/Qb Where; C e is the equilibrium concentration of ammonia in solution. C ads is the concentration of ammonia adsorbed onto zeolite. Q is Langmuir constants related to sorption capacity. B is Langmuir constants related to sorption energy. The Langmuir constant (Q and b) were calculated from slope and intercept from the linear equations. The obtained Langmuir constant (Q and b) were compared with experimental results for preliminary adsorption for checking of the accuracy and consistency between them. R 2 of all linear equations were considered for the reasonable isotherm model. Results, Discussion and Conclusion : Preliminary adsorption study by using two natural zeolites Batch adsorption is used to remove ammonia using two natural zeolites classified as Offretite and Clinoptilolite. For condition used in preliminary study, 40 g/l of natural zeolites were suspended in 30 ppm ammonia solution for an hour. The aim of this part is to study removal efficiency and the feasibility of using natural zeolites as adsorbent material for removal ammonia in synthetic aqueous solution. The result of preliminary adsorption study is showed in Table 1. Table 1. Preliminary adsorption study of ammonia using two natural zeolites Natural zeolites Average ammonia adsorption Adsorption efficiency (%) Offretite Clinoptilolite In Table 1, the results show average ammonia adsorption efficiency of 40.16% and 92.10% for Offretite and Clinoptilolite, respectively. It is observed that the adsorption efficiency of ammonia for Clinoptilolite is higher than Offretite. Investigation of optimum condition for ammonia removal using Clinoptilolite The result is the second part of the application of natural zeolite Clinoptilolite for removal of ammonia from prepared aqueous solution at laboratory scale. The following parameters were selected to study optimum condition. Effect of zeolite amounts, adsorption time and initial ammonia concentration were studied. According to Table 1, from preliminary adsorption study, the results show Clinoptilolite given highest adsorption efficiency of ammonia aqueous solution. It is approximately 92% for removal of ammonia solution. Then Clinoptilolite were selected to further study. - Effect of zeolite amount 37 th Congress on Science and Technology of Thailand 3

4 Study of the effect of zeolite amount was performed by varying Clinoptilolite form 0.50, 1.00, 1.50 and 2.00 g. Results of the adsorption efficiency of the effect of zeolite amount was calculated and present in Figure 1. Figure 1. Effect of zeolite amount on adsorption efficiency. Figure 1. shows 1.0 g of Clinoptilolite in 25 ml of 30 ppm with 93.8% ammonia adsorption efficiency is an optimum amount for removal of ammonia. - Effect of adsorption time It is necessary to know the optimum adsorption time to obtain optimum ammonia adsorption of Clinoptilolite. The effect of adsorption time was studied by varying the adsorption time with 15 minutes, 30 minutes, 1 hour, 2 hours and 6 hours. Systematic perturbation was carried out by magnetic stirrer every 30 minutes for 30 seconds. The result of adsorption efficiency of effect of adsorption time was calculated and presented in Figure 2. Figure 2. Effect of adsorption time on adsorption efficiency. It is found that an hour adsorption time is required to reach the optimum adsorption of ammonia on Clinoptilolite with approximately 95% adsorption efficiency. - Effect of initial ammonia concentration 37 th Congress on Science and Technology of Thailand 4

5 To obtain the completely optimum condition for ammonia adsorption, effect of initial ammonia concentration on adsorption of ammonia by varying ammonia solution in the concentrations of 5.00, 10.00, 20.00, 30.00, and ppm. The results of adsorption efficiency of the effect of initial of ammonia concentration was calculated and presented in Figure 3. It can be seen that the adsorption efficiency of ammonia from aqueous solution decreases with increasing the initial concentration. Figure 3. Comparison of adsorption efficiency of ammonia by Clinoptilolite on the effect of initial ammonia concentration. Adsorption isotherms study The adsorption data of ammonia using Clinoptilolite as an adsorbent has been subjected for study. Freundlich and Langmuir isotherms were selected to study the effect of initial ammonia concentration concerning adsorbed behavior onto the natural zeolite. The obtained experimental data are expected with the linearized form of two mathematic models, as shown in Figure 4 and summarize in Table 2. Figure 4. Adsorption isotherm of ammonia on Clinoptilolite (4A. Freundlich Isotherm, 4B. Langmuir isotherm.) 37 th Congress on Science and Technology of Thailand 5

6 Table 2 Summary of equilibrium isotherm for ammonia adsorption with Clinoptilolite. Isotherm model Parameters R 2 Langmuir K L N M y = x Fruendlich K f 1/n y = x From Figure 3 and Table 2, the Langmuir model effectively describes the adsorption data with R 2 value is The Fruendlich model effectively describes the adsorption data with R 2 value is Langmuir isotherm has a better correspondence with the experimental finding rather than Fruendlich isotherm. Conclusion. In summary, the finding of this research indicate that clinoptilolite, a natural zeolite, can be successfully applied as an effective adsorbent for removal of ammonium ion from aqueous solution. Basic conditions such as adsorbent usage, contact time and initial concentration influence the removal of NH4 + ion from aqueous solution by clinoptilolite. Equilibrium isotherm data was fitted to the linear Freundlich- and Langmuir models with the latter model providing the better description of the process compared to the former. Based on the obtained results, clinoptilolite is recommendable adsorbents for highly ammonium ion removal efficiency from industrial wastewater treatment with high efficiency and relatively low cost materials. References : 1. B. Ducourty.; M.L. Occelli.; A. Auroux., Processes of ammonia adsorption in gallium zeolites as studied by microcalorimetry. Thermochimica acta. 1998, 312, Haiming, H.; Xianming, X.; Bo, Y.; Liping, Y., Ammonium removal from aqueous solution by using natural Chainese (Chende) zeolite as adsorbent. Journal of hazardous materials.2010, 175, Jumras, L.; Usa, O., Coadsorption of ammonia and methanol on H-zeolites and alkalineexchanged zeolites. Journal of molecular structure. 1997, 435, Sirinate, S. The adsorption of ammonia from aqueous solution in laboratory scale by using natural zeolite. Research. Faculty of science Ubon rajathanee University, Xue, L.; Cong, L.; Yang, W.; Ming, Z.; Yu, H., Clinoptilolite adsorption capability of ammonia in pig farm. Procedia environmental sciences.2010, 2, Acknowledgements : This work was supported by Ubon Ratchathani University. Keywords: Ammonia, Adsorption, Natural zeolites 37 th Congress on Science and Technology of Thailand 6