Lead removal from aqueous solution by natural and pretreated clinoptilolite: adsorption equilibrium and kinetics.

As agriculturalists increase their efforts to expand crop and animal production, numerous mineral materials are receiving greater at tent ion as soil amendments and as dietary supplements in animal husbandry. The zeolite group of minerals stands out among the rest, and its exciting bag of physical and chemical tricks promises to contribute to many areas of agriculture and aquaculture in the ne~t decade. Their abundance and availability has aroused considerable interest in experiment stations of several nations, although the number of publications and amount of \"hard\" data on their usefulness in agriculture are still small. A review of this subject reveals that both the ion-exchange and adsorption properties of natural zeolites can be exploited to make more efficient use of feed nitrogen in animal nutrition, to reduce intestinal diseases prevalent in young swine and ruminants, to control moisture and ammonia content of animal manure, to purify recirculating hatchery waters in aquaculture, to provide oxygen-enriched air for fish breeding and transportat ion, and to reduce the nitrogen content of feedlotand hatchery-runoff waters. Most of this work has been carried out in Japan where zeolitic tufts have been used for years to control the malodor of animal wastes and to raise the pH of acidic volcanic soils. The addition of about 10% clinoptilolite to the diets of chickens and pigs appears to increase feed efficiency by as much as 25%. Studies in Japan

The Application of Natural Zeolites in Animal Science and Aquaculture

Ammoniacal nitrogen removal from water by treatment with clays and zeolites

Characterization and environmental application of a Chilean natural zeolite

The unique treedimensional porous structure gives natural zeolites various application possibilities. Because of the excess of the negative charge on the surface of zeolite, which results from isomorphic replacement of silicon by aluminum in the primary structural units, natural zeolites belong to the group of cationic exchangers. Natural zeolites have advantages over other cation exchange materials such as commonly used organic resins, because they are cheap, they exhibit excellent selectivity for different cations at low temperatures, which is accompanied with a release of non-toxic exchangeable cations (K+, Na+, Ca2+ and Mg2+) to the environment, they are compact in size and they allow simple and cheap maintenance in the full-scale applications. The efficiency of water treatment by using natural and modified zeolites depends on the type and quantity of the used zeolite, the size distribution of zeolite particles, the initial concentration of contaminants (cation/anion), pH value of solution, ionic strength of solution, temperature, pressure, contact time of system zeolite/solution and the presence of other organic compounds and anions. For water treatment with natural zeolites, standard procedures are used, usually a procedure in column or batch process. More careful consideration of their superb metal removal properties and awareness of possible regeneration or further use of contaminant/metal-loaded forms can considerably increase their environmental application possibilities, with a focus the reduction of high concentrations of cations and anions in drinking water and wastewater, for surface, underground and public municipal water treatment independently or in combination with others physical - chemical methods.

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Natural Zeolites in Water Treatment – How Effective is Their Use

Early in the developing science of water pollution control, the presence of ammonia in groundand surface water supplies was regarded as a strong indication of recent pollution (1). Klein (2) has stated that am monia concentrations of greater than 0.2 mg/1 are a strong indication of pollution by wastewater. More ex plicitly, McKee and Wolf (3) state that: "The generally accepted limit for free ammonia for sanitary purity of water supplies is between 0.05 and 0.10 mg/1. Excess of this value ren ders the water suspect of recent pollu tion." While ammonia-nitrogen is commonly observed in surface waters, it is not found in groundwaters ex cept in small amounts under anaerobic conditions (4). As water quality science progressed, it became apparent that the presence of ammonia in water has far more seri ous implications than merely serving as an index of recent pollution. It was demonstrated that:

https://www.jstor.org/stable/info/25036497

R B Dean

Papers

Ammonium removal from secondary effluents by selective ion-exchange