A study of the application of clinoptilolite as an ion exchange agent for selected metals in aqueous solution
- Authors: Dyeshana, Vuyokazi
- Date: 2012
- Subjects: Ion exchange , Clinoptilolite
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10419 , http://hdl.handle.net/10948/d1013257
- Description: The aim of this study was to establish whether samples of South African-mined clinoptilolite could be used to remove selected metal cations from aqueous solution. The clinoptilolite samples supplied, (by Pratley SA) were in four different particle sizes. Batch study results revealed a decrease in the initial metal concentration in samples that were in contact with clinoptilolite. The finer particle size clinoptilolite had a greater capacity to remove metal cations from aqueous solution. However, ion-exchange results from atomic absorption analysis showed that the larger particle sizes, removed more magnesium ions. Magnesium was the only ion investigated in this study that was present as an exchangeable ion in the Pratley clinoptilolite chemical formula, (MgCaNa2K2)2.5(AlO2)7(SiO2)30.21H2O. Results from the ion-exchange studies showed that the decreasing order of percentage metal removal at pH 3.00 was as follows: Pb > Ni > Cu > Fe > Mg. The mass of metal ions that accumulated on one gram of clinoptilolite as determined from the isotherms was calculated to be 6.16 mg/g for lead and 0.74 mg/g for copper. Data from the lead equilibrium studies were fitted into Langmuir and Freundlich equations and linear regression was used to calculate linearity coefficients for the isotherms. The results showed that the removal of lead ions by clinoptilolite is complex as both monolayer and multilayer adsorption occurs on a heterogeneous surface.
- Full Text:
- Date Issued: 2012
Ammonia removal from water by ion exchange using South African and Zambian zeolite samples
- Authors: Mwale, Monica
- Date: 2000
- Subjects: Ammonia -- Toxicology , Water -- Purification , Zeolites , Ion exchange
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5215 , http://hdl.handle.net/10962/d1005058 , Ammonia -- Toxicology , Water -- Purification , Zeolites , Ion exchange
- Description: One problem of intensive fish culture systems is the progressive build-up of toxic wastes such as ammonia. The possibility of improving aquaculture water quality using two kinds of zeolite is discussed. Zeolites are alumino-silicates whose framework allows them to exchange cations. Ion exchange has been demonstrated to be competitive with other methods of ammonia removal due to the high selectivity for ammonia exhibited by zeolite materials. In this study an unknown Zambian zeolite (identified as laumontite by X-ray diffraction techniques) and Pratley clinoptilolite (a South African zeolite) were tested under laboratory conditions and in a fresh water recirculating system. Ammonia cation exchange capacities (CEC) and suitable application rates for efficient water treatment were determined using the batch and column ion exchange procedures. Estimated ammonia uptake, the most important criterion used to assess performance of zeolite filters was strongly influenced by zeolite type, particle size, pre-treatment, regeneration and ion exchange method used. Statistical analysis showed significant differences in average ammonia CEC values between clinoptilolite (14.94 mg g⁻¹) and laumontite (2.77 mg g⁻¹), with the former displaying a higher Na⁺ ® NH₄⁺ exchange rate especially in the early reaction stages. This difference accords with the higher purity of clinoptilolite, 47% as opposed to 4.7% for laumontite, which makes it a better zeolite for ammonium removal. CEC increased linearly as particle size of the clinoptilolite was reduced resulting in a linear regression model (y = 18.29 – 3.704 x; r² = 74%). Pre-treatment of clinoptilolite using 1N NaCl significantly improved the ammonia CEC of clinoptilolite. Overall performance of both the batch and column methods achieved after regeneration (18.3 mg g⁻¹) was 25% higher than the estimated CEC values (13.0 mg g⁻¹) for the unregenerated samples of clinoptilolite. Comparison of CEC estimates using Pratley clinoptilolite, showed that average batch CEC estimates were significantly lower than the column method estimates. The average ammonia CEC values estimated in a fresh water recirculating system (5.80 mg g⁻¹ and 4.12 mg g⁻¹ for the 0.7-1.0 and 1.0-1.4 mm particle sizes, respectively) were significantly lower than the column and batch estimates for the same particle sizes (P < 0.05). Some nitrite (NO₂) and nitrate (NO3) build up was experienced probably due to the growth of autotrophs in the filters. Mass balance of nitrogen (N) for the three treatments of the fish trial (0.7-1.0 mm, 1.0-1.4 mm and the control treatment that had no zeolite in the filter) indicated that less that 10% of the N was retained for growth. It was found that 60% of the NH₄-N present associated with the soluble N was available for absorption by the zeolite filter or biological nitrification and that a total of approximately 22% of NH₄-N available was absorbed by clinoptilolite. The results indicate that the rate of nitrification can be deductively estimated by allowing a zeolite filter to become a biological filter. It is concluded that water treatment by ion exchange using natural zeolites, provides a reliable and efficient method for ammonia removal and appears to be a viable supplementary water treatment method for fresh water systems.
- Full Text:
- Date Issued: 2000
A study of cation exchange in South African soils
- Authors: Du Toit, A A
- Date: 1952
- Subjects: Soil chemistry , Ion exchange
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4462 , http://hdl.handle.net/10962/d1011506 , Soil chemistry , Ion exchange
- Description: The colloidal fraction is the vital part of a soil. These extremely minute particles determine the nature of the soil and are mainly responsible for its many and varied functions. The most important of these functions is perhaps the ability of the colloids to adsorb and exchange cations, the elements so essential to all organisms as building materials. When pure water is passed through a non-saline. soil, the leachate will contain very few dissolved cations. If, on the other hand, an electrolyte such as a weak solution of sodiun chloride, is passed through the same soil, the leachate will contain considerable quantities of calcium, magnesium and potassiun chlorides as well as much of the original sodium chloride. The number of equivalents of the cations collected will be approximately the same as the number of equivalents of sodium ions added. Sodium ions have displaced some of the calcian, magnesium and potassium ions from the soil. This phenomenon is known as cation exchange. Intro., p. 1.
- Full Text:
- Date Issued: 1952