Handbook of Natural Zeolites

The term zeolite coming from the Greek words, which mean stone that boils, was originally coined in the 18th century by a Swedish mineralogist named Cronstedt. A zeolite is a crystalline aluminosilicate with a cage structure. Natural zeolites combine comparative simplicity of mining, relatively low cost, worldwide distribution and in combination with their unique physicochemical properties they became the most important minerals. The zeolite group includes more than 40 naturally occurring species, some of them are rare, all beautiful with diverse complexity and unique crystal habits.

In the 20th century, in particular from 1930 to 1970, synthetic zeolites were used in most commercial applications. Gradually, due to large deposits being discovered all over the world, low price and good performance in several applications, natural zeolites found their way into the market. The applications of natural zeolites are numerous and enterpreneurs around the globe pay more and more attention to products and technologies based on these extraordinary materials. As a result, there is a worldwide trend to increase production and consumption of natural zeolites and to perform technical studies focused on the development of new products of high added value. This Chapter does not aim to establish rules or to provide robust directions for decisions and actions of entrepreneurs and scientists involved in commercialization projects employing natural zeolites but to raise some issues for brainstorming and to provide some insight in the fascinating world of zeolites business.

Zeolites are the main mineral components in altered volcaniclastic rocks ranging in age and composition. They form by alteration mainly of volcanic glass in various geological environments, under variable geochemical and temperature conditions. Proposed genetic models of zeolite deposits include weathering, diagenesis in open or closed hydrologic systems, low temperature hydrothermal systems, primary magmatic environments and impact craters. The most common zeolite species, which may occur in mineable deposits, are clinoptilolite-heulandite, mordenite, chabazite, analcime, and phillipsite. Mineable zeolite deposits are widespread in many countries worldwide. The world annual production of natural zeolites remains essentially constant over the last 10 years at ca 3 million tons. Although several large high grade zeolite deposits are currently under operation and numerous studies on the suitability of the zeolite materials in various applications have been carried out, most of the annual zeolite production is consumed in massive low value applications like additives in pozzolanic cement and lightweight aggregates.

Zeolites are crystalline, hydrated aluminosilicates of alkali and alkaline – earth cations having infinite three dimensional structures. Zeolites occur in a variety of geologic settings, mostly as alteration of authigenic minerals, low temperature-low pressure minerals in metamorphic systems, secondary minerals in weathered zones, or in veins. Nine zeolites commonly occur in sedimentary rocks: analcime, chabazite, clinoptilolite, erionite, ferrierite, heulandites, laumonite, mordenite and phillipsite. Analcime and clinoptilolite are the most abundant. Zeolite minerals with commercial potential are limited to five: chabazite, clinoptilolite, erionite, mordenite and phillipsite. The most important properties of zeolites are: ion exchange, adsorption, dehydration and rehydration. These properties are dependent on the specific crystal structure of each species, its framework and cationic composition. In characterizing zeolitic materials for commercial uses, it is important to quantify other physical and chemical properties. The following are physical and chemical properties and tests that may typically be required: cation exchange capacity (CEC), specific gravity and bulk density, brightness, whiteness and color, hydration/dehydration testing, gas adsorption, attrition in water, surface area (internal and external).

A zeolite can be imagined like a house, where the structure (the doors, windows, walls and roof) is really the zeolite while the furniture and people are the water, ammonia and other molecules and ions that can pass in and out of the structure. The chain - like structures can be thought of like towers of high wire pylons. The sheet – like structures can be seen like large office buildings with the sheets analogous to the floors and very few walls between the floors. And the framework structures like houses with equally solid walls and floors. All these structures are still frameworks. These variations make the zeolite group very diverse, crystal habit – wise. Otherwise zeolites are typically soft to moderately hard, light in density, transparent to translucent and have similar origins. There are about 45 natural minerals that are recognized members of the Zeolite Group. In this chapter are presented the main physicochemical properties of zeolites in correlation with their structure. From this point of view there are three large families of zeolites: the natrolite group, the heulandite group and the chabazite group. For each zeolite families the main representing members are presented together with their properties.

Zeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents. Zeolites also crystallize in post-depositional environments over periods ranging from thousands to millions of years in shallow marine basins. Naturally occurring zeolites are rarely pure and are contaminated to varying degrees by other minerals, metals, quartz, or other zeolites. For this reason, naturally occurring zeolites are excluded from many important commercial applications where uniformity and purity are essential. Zeolites have been shown to be useful catalysts in a large variety of reactions, from acid to base and redox catalysis.

Zeolite is micro-porous crystalline mineral having a highly regular structure of pores and chambers usually occupied by H₂O molecules and extra-framework cations that are commonly exchangeable. The different zeolites differ in pore diameter and shape and the way these pores are interconnected. In this Chapter the basic principles of the natural zeolites framework and porosity are presented.

To date, a variety of sorbents have been used to immobilize pollutants in contaminated soils and water. Immobilization can be achieved by adding natural and synthetic amendments such as alkaline materials, phosphate minerals, Fe and Mn hydroxides, aluminosilicates and zeolites. Because of unique structure, high cation exchange capacity, low cost and wide spread availability, zeolites are probably the most promising materials interacting with many organic and especially inorganic ions in contaminated soils and water. In the fields of soil and water pollution and remediation, the sorption and desorption play a key role on transport and availability of pollutants. Extensive researches have been focused on contaminant sorption by zeolites. However, desorption behavior of pollutants from zeolite minerals are still poorly understood. For several pollutants, the desorption pathway is different from that of the sorption. This phenomenon is known as hysteresis. Sorption hysteresis of environmental sorbents such as zeolites has important implication for the pollutant transport and bioavailability.

Pretreatment of natural zeolites covers a wide range of modification techniques leading in several products to a variety of applications. A very common pretreatment type is used for producing modified zeolites for use in ion exchange applications and in particular for the removal of cations from aqueous solutions. In these cases, pretreatment aims to remove certain ions from the structure of the material and locate more easily removable ones, prior to any ion exchange application. Practically, the result of any pretreatment operation is the increase of the content in a single cation, what is called homoionic form. The final homoionic or near homoionic state of the zeolites improves the effective exchange capacity and performance in ion exchange applications.

In this chapter we address the modification of the surface properties of zeolites. The first method discussed is the attachment of long chain surfactant molecules to enable the sorption of anionic and non-polar species. The second method is known as silation, where the presence of silanol groups on the zeolite surface are exploited to form a hydrophobic material.

Zeolites have been recognized for more than 200 years, but only during the middle of the 20th century have attracted the attention of scientists and engineers who demonstrated their technological importance in several fields. Although most of the effort was devoted to synthetic zeolites, in recent years increasing attention has been directed towards natural zeolites, whose status changed from that of museum curiosity to an important mineral commodity. Natural zeolites forming the corresponding group of tectosilicate mineral subclass, due to their specific crystal chemical characteristics providing the unique ion exchange and molecular sieve properties, are known as effective adsorbents and catalysts. The zeolites are highly rigid under dehydration as well as under various aggressive surroundings actions. The molecular sieving and other physico-chemical properties of the zeolites can be managed by the thermal or chemical treatment. Such features provide the effective and wide utilization of these materials in industry, agriculture, medicine, environmental protection and other fields. Synthesized analogues of the natural zeolites are usually applied in different technological processes, and the low output price conditioned by a subsurface location of massive deposits of natural zeolites throughout the world make them significantly more available for a wide utilization. Main fields of industrially important zeolite rocks are presented by clinoptilolite (or mordenite, chabazite, phillipsite, etc.) tuffs and are connected with volcanic formations.

Currently, there is a rapidly emerging crisis involving the access of clean drinking water due to the increasing release of various pollutants by industries to the environment. Industrial wastewater streams contain a wide range of pollutants from toxic cationic and anionic species, to extremely poisonous organic compounds, which are very harmful to humans and the environment. Therefore, the development of novel, efficient, and inexpensive technologies for the decontamination of polluted waters, soils, and the air is essential. Amongst the variety of techniques that have been developed to treat contaminated areas in the environment; adsorption-based processes are believed to be the most simple and effective techniques which largely depend on the development of efficient adsorbents. Generally, adsorbents based on zeolitic materials are known to be safe for the health of humans and the well-being of the environment. To date, many zeolite-based products have been developed to degrade heavy metals and organic toxins within the environment, and even in the human body. In this paper, some of the recent achievements of the potential applications of natural zeolites; particularly their surface modified forms for the removal of anions, cations, and organic pollutants from contaminated waters and soils will be discussed.

The scope of this chapter is to present a review of relatively recent research work on operations and processes that involve the interaction of natural zeolites with organic vapors or gases, in a simple and comprehensive way. The time horizon for the bibliographic search was set at 20 years back. Modified natural zeolites have also been included, since a modification step (most usually by ion-exchange) of the naturally occurring materials is usually considered essential prior to any use.

There are three kinds of sludge: sewage sludge from municipal treatment works, septage pumped from septic tanks, and industrial sludge. All three are a growing management problem in this state, and throughout the world. Problems associated with sewage sludge disposal and treatment remains a challenge for the waste industry and for many researches around the world. Sludge is presented with significant issues like heavy metals, nitrogen, phosphorous, pathogens, organics etc. Some them when added to soil is necessary to control the consecration due to potential toxicity and especially the heavy metals like Cr, Cd, Cu, Pb, Zn, Cd, Hg, Co, Ni etc. Natural zeolites are a popular group of minerals for collectors and an important group of minerals for industrial and other purposes. Zeolite utilization has become popular in the last decade, due to its cation exchange and molecular sieving properties. Zeolites have many useful purposes. They can perform ion exchange, filtering, odor removal, and chemical sieve and gas absorption tasks. Many researchers investigated the use of natural zeolites in several applications of sewage sludge and they found out the final products presented with excellent characteristics. This chapter presents the use of zeolites in sewage sludge and other treatment.

In this chapter, the use of natural zeolites (clinoptilolite) in medical applications is reviewed. Zeolites have been investigated as feed additives in animal nutrition for the prevention of certain diseases and the improvement of animals’health status. The dietary use of zeolites has been shown to sequester mycotoxins and reduce their absorption from the gastrointenstinal tract. The beneficial effect of zeolites on aflatoxicosis is also reported. Research data reported in the published literature provide evidence that they can be used for the prevention of milk fever and ketosis in dairy cows. Their effect on gastro-intestinal infections is reported and more specifically their use as an anti-diarrheic drug and also for their antacid activity. Furthermore, several studies report their use as carriers and releasers of active ingredients, and this can be used in anti-acne therapy. They are also used as adjuvant in anticancer therapy. When applied externally in powder form, zeolite has also been found to quicken the healing of wounds. Finally, it is reported that they can be used as antibacterial material. It also should be noticed that several studies report their non toxicity and safety of their use in animal nutrition.

The processes of new C-C bond formations are crucial for the organic synthesis. The application domains of the reactions proceeding with formation of new C-C bonds have constantly developed along with the development of the world-wide economy branches. Thus, starting from raw materials such as oil, coal and natural gas a great variety of complex organic compounds are obtained that can be used to prepare numerous synthetic products such as: drugs, dyes, pesticides, cosmetics, detergents, etc. Such transformations are possible to be achieved due to the organic chemistry development, especially the synthetic chemistry where the structures can be converted and new C-C bonds created. The majority of these reactions proceed by mechanisms involving reaction intermediates. In the first section of the present chapter the condensation reaction of the carbonyl compounds and the corresponding reaction mechanism are briefly presented. In order to improve the obtaining methods of the resulting products (increasing in the specific reaction rate, minimization of the side products, the reaction directing straight to the final product, etc.) the presence of either homogeneous or heterogeneous catalysts is quite necessary. Among the numerous catalytic processes with C-C bond formation those based on the aldol condensation in heterogeneous catalysis are the most important and thoroughly studied. The synthetic catalysts usually taken in such processes are described in the second section of the present chapter where the reaction mechanisms with both acid and base catalysis are given. Apart from the synthetic catalysts the natural zeolites deserve mention due to their advantages as efficient catalysts of a low price. The material in the final two sections of this chapter is focused on the clinoptilolite in the zeolite volcanic tuff as well as on its properties studied and tested in the aldol condensation reaction of acetaldehyde with formaldehyde.

Solar energy, the power derived from the rays of the sun, is considered to be one, if not the most environmentally friendly source of energy that can be used on earth. The energy storage is one of the critical problems of present solar energy application research. Due to their structure, zeolites are able to store solar energy and to be showed off due to their propriety of adsorbing/desorbing water without damage the structure. The great advantage of thermal energy storage methods based on adsorption/desorption processes consists in the possibility of storing thermal energy, even for long time. Zeolites answer both to requirements of large availability and low cost.

In 1995 during the Zeolite Meeting' 95 in Sofia, Bulgaria, Ivanova et al., entitled their paper on the use of natural zeolites in space applications as “Zeolite Gardens in Space”. This Chapter presents the subject of natural zeolites in space applications and occurrence in extraterrestrial environments. The Chapter is dedicated to Frederick A. Mumpton and Robert S. Bowman whom I had the luck and the honor to meet in Thessaloniki, Greece in 2002 during the 6th International Conference on the Occurrence, Properties and Utilization of Natural Zeolites. I hope the gardens in space to be wide open to them.

A decade of Swedish academic research on zeolites used for improved nutrient recovery from decentralized domestic wastewater treatment is presented here. Especially source separating systems (urine separation) for toilet wastewater were developed since the late ´80s in northern Europe and sustainable ways of nutrient use and reuse were tested and introduced aiming not only to close the nutrient cycles and render them safe, but also to close local water cycles. In this way, sustainable nutrient and water management also significantly contribute to solve a number of problems like eutrophication, hygienic issues, water pollution with organic and inorganic toxic pollutants, endocrine disruptors, drug residues, etc. However, source separation and separate handling of toilet wastes are not problem-free: collection, storage and handling of human excreta, transport and acceptance of nutrients by the farmers, spreading and farm-management are still not fully developed. To meet almost all of the above presented problems, new, simple and robust technologies using zeolites and struvite formation as main steps to recover nutrients (e.g., N, P, K, Ca, Mg, S) from human excreta (especially urine) and transform them in solid, easy manageable fertilizers can be a real option. The central role of zeolites (especially clinoptilolite) in the nutrient (N and P) recovery from separated human urine is in focus in this presentation. The results clearly show that the quality of zeolite, the grain size and the ionic strength of the solution (urine) affect the process. N uptake by zeolite in combination with struvite precipitation (MgO addition to urine) could recover 64-80% of the N and 100% of the P in laboratory tests. The N recovery from fresh and stored human urine is a complex process affected by both the amounts of MgO and zeolite added. MgO contributes to struvite formation with ca 10% uptake of the ammonium-N in urine and the added zeolites can ion-exchange the rest. To some extent the P recovery through MgO addition was affected also by the zeolite adsorbing small amounts of P probably on its structural sites (hydrous oxides). Optimal combined recovery of N and P occurred at added concentrations of 0.1 g of MgO and 15-30 g of zeolite per liter stored and diluted urine and is dependent on the initial N and P concentrations of the urine. The changes in pH and the acute toxicity to Daphnia magna of the remaining supernatant solutions indicate some ampholitic behaviour of the zeolite in contact with neutral to strongly basic solutions. The zeolite itself showed to be non-toxic in the toxicity tests. Shortterm climate chamber experiments on wheat and barley showed that the nutrients recovered from urine as zeolite-struvite mineral mix (ZSM) and used in proper amounts act as a good nutrient source, fully comparable with DAP (di-ammonium-phosphate) and CaP (mono-calcium-phosphate) slow release commercial fertilizers.

This review article highlights the characteristic features of adsorption and ion exchange materials for environmental cleanup processes, especially for water purification, with an emphasis on the recent developments in this field, particularly in synthesis and manufacturing of the advanced cost-effective organic-inorganic (hybridized) zeolite-based adsorbents. An organic-inorganic composite adsorbent termed as a hybrid material too, may be defined hereto as a combination of a polymerous substance immobilized onto surface of the inorganic e.g., zeolite carrier to avail advantages of both zeolitic and polymerous constituents as well. Accordingly, hybridization can be used to modify organic or inorganic materials and hybrids should therefore be considered as the new generation of composites that may encompass a wide variety of applications. The conversion of inorganic ion exchange materials into hybrid fibrous or nanoscale ion exchangers is considered to be the latest development of this discipline. These nanomaterials are drawing a great attention as they exhibit a high efficiency and rate of sorption with short diffusion path towards environmental pollutants. Advances in nanoscale science and engineering are providing unprecedented opportunities to develop more cost effective and environmentally acceptable water purification processes, respectively. For the water purification, besides the metalcontaining nanoparticles, carbonaceous materials and dendrimers, also the zeolites are being evaluated as the most progressive functional and nanosized materials of the millennium. A progress in marketing natural zeolites is encouraging, given that natural zeolites are being considered to be a commodity of great potential since the industry´s beginning in the late 1960s. Zeolite unique market position is progressing by continued development of their ion exchange and adsorption properties and especially through their surface treatment. The zeolite crystal structure is unique, in contrast to silica gel or traditional activated carbon adsorbents, in uniform pores distribution. This distribution limits the filling of zeolite micropores volume on the basis of the relative sizes of adsorbates and their states of solvation inside and outside the zeolite. Mesoporous organosilica (MOS) by which the structural characteristics arise from the used surfactant micelles and the final framework is usually amorphous, have attracted lately a great interest in analytical and preparative chromatography and organic pollutants removal, too. In spite of many progressive characteristics of recent MOS, regarding to zeolite, this potential adsorbent does not pose a shape selectivity, such as that found in the molecular sieving effect of crystalline zeolite, is hydrothermal instable, fragile and currently for massive technical applications still too expensive. A laboratory set-up was used also to examine the uptake of mono- and polyatomic single or mostly double charged anions like chromate, arsenate, nitrate, sulfate, phosphate, halogenides and some organic substances like azodyes (acid red, indigo carmine) and phenol from aqueous model solutions by the octadecylammonium (hereafter ODA) modified, carbonized or alginate pelletized clinoptilolites. The adsorption isotherms of the systems studied are usually expressed and mathematically fitted according to the adsorption isotherm models of Freundlich, Langmuir, Brunauer-Emmet-Teller. Removal efficiencies of the surface functionalized clinoptilolites towards above water pollutants are compared and evaluated with the other low-cost natural or commercial adsorbents, like activated charcoal, pyrolysis char, lignite and expanded perlite, respectively.

Сlinoptilolite-containing tuffs as ion-exchangers play an important role in water decontamination. The shortest scientifically grounded way to determine the optimal conditions or to forecast the results of ion-exchange processes lies in the mathematical modeling of both sorption and regeneration stages. The theory of the ion-exchange dynamics has been developed and used for modeling and calculation of technological tasks on ion-exchange resins. A bank of solutions for the dynamic ion-exchange tasks was created in the Laboratory of Sorption Methods of the Vernadsky Institute. The ion exchange on natural zeolites – clinoptilolites is characterized by a number of specific features, particularly, two-stage particle diffusion kinetics. The possibilities for using available solutions of sorption dynamics for modeling and calculation of the ion-exchange processes on natural zeolites were estimated. It was shown that the use of available solutions is possible if the sorption of target components is described by linear or nearly linear isotherms. The actual examples of application of known theoretical solutions of the sorption dynamics for modeling and calculating of ion exchange processes on natural clinoptilolites are presented in this article. The breakthrough times of some technological filters loaded with clinoptilolite are also calculated.

Environmental pollution particularly at very low concentrations is very difficult to remove from contaminated media. Adsorption by means of relatively inexpensive natural adsorbents such as zeolites can be considered as a cost effective alternative treatment of such contaminated streams. The unique chemical and structural characteristics of natural zeolites made them potential materials for a multitude of environmental applications where materials are needed for effective binding, adsorbing, and filtering. In this chapter, some of the commercially available environmental treatment technologies based on utilization of natural zeolitic materials will be discussed.

Information presented here focus on the sustainable commercial use of natural zeolites. Topics specifically covered include; (i) use of this natural mineral for remediation of contaminated sites and clean-up of spills, (ii) treatment and handling of animal/agricultural wastes considering recent climate change policies, (iii) management of wastewater treatment plant sludges to enable valuable product formation and prevention of formation of hazardous wastes. Reuse of spent zeolites and future trends in terms of their commercial use, together with potential limitations are also discussed.

Zeolites, natural and synthetic, have been widely studied regarding their suitability to be used in many different environmental applications worldwide. Their unique structure of channels, cavities and cages results in large internal surface available for a variety of reactions, which could also be applied for the protection, improvement and also remediation of soil quality. Soil is a key component of natural ecosystems and environmental sustainability depends largely on a sustainable soil ecosystem. Unlike other environmental compartments (e.g., atmosphere, water) pollutants have long residence times in soil while the overall degradation or, finally, the destruction/collapse of a soil system and, consequently its ecosystem, could be appeared many years after the beginning of its degradation. This is due to its capability to act as filter and natural bio-degrader for a lot of organic and inorganic elements and compounds, capability which, however, could be exhausted due to continuous disposal of excess nutrients, harmful and toxic compounds. Many soil remediation techniques have been developed and applied so far; some of them include the use of natural zeolites and mainly clinoptilolite. However, the most of the obtained results, regarding their suitability to be used as soil amendments for remediation purposes, have been obtained through lab experiments and small scale field applications. Regardless the limited extension of their application on real problems of soil pollution (except the case of land application after Chernobyl disaster), there are plenty of research works that deal with the potential of zeolites to be included in the inventory of the effective and efficient amendments for soil remediation. Some of these research studies, are presented in this review work aiming, not to cover the entire literature, but to provide representative data and evidence for zeolites effectiveness also in soil remediation. In addition, results are provided regarding the use of clinoptilolite as soil amendment for the protection and improvement of soil quality degraded due to the disposal of Olive Oil Mills Wastes, which were obtained from a study funded within a European LIFE project. This research field is considered as highly innovative since it has never been studied before.

Natural zeolites are abundant and low cost materials available all over the world. Due to their highly developed porous structure, these materials exhibit high capacity for gas adsorption and selectivity for separation. In the report, the structure and characteristics of natural zeolites related to gas adsorption and their application in gas separation are briefly reviewed. Natural zeolites can be used for gas drying due to having high adsorption capacity of water. They can also be used for cleaning of natural gas and flue gas.

Zeoponic plant growth media is a media composed of enriched zeolite substrate containing some of the essential plant growth nutrients on their exchange sites. In addition to the exchangeable cations, the substrate usually contains minor amounts of other solid phase minerals supplying essential buffering ions and micronutrients. Various types of zeoponic systems have been developed so far. In these systems zeolite supplies K and NH4, apatite supplies Ca, P, Mg, S, Fe, Mn, Zn, Cu, B, Mo, Cl and other calcium bearing minerals such as calcite and dolomite provide supplementary Ca and Mg and there is little or no need to supply nutrient elements to this system. In fact, these systems act similar to the slow release fertilizers gradually providing the required essential elements for plant growth. So far, different kinds of zeoponic systems have been developed and National Aeronautics and Space Administration (NASA) researchers had a key role in developing and modifying these systems. The present chapter describes some properties, advantages and disadvantages of zeoponic systems.

Clinoptilolite {(Na, K, Ca)2 - 3Al3(Al, Si)2Si13O36-12H2O, Hydrated Sodium Potassium Calcium Aluminum Silicate} may be not the most well known, but it is one of the most useful natural zeolites. Clinoptilolite is used in many applications such as a chemical sieve, a gas absorber, a feed additive, or food additive, an odor control agent and as a water filter for municipal and residential drinking water and aquariums. Clinoptilolite is well suited for these applications due to its large amount of pore space, high resistance to extreme temperatures and chemically neutral basic structure. What might strike many as odd is the food and feed additives. Clinoptilolite has been used for several years now as an additive to feed for cows, pigs, horses and chickens. It absorbs toxins in the feed that are created by molds and microscopic parasites and has enhanced food absorption by these animals. A similar use in actual people food is being tested. Zeolites can easily absorb ammonia and other toxic gases from air and water and thus can be used in filters, both for health reasons and for odor removal. Can zeolite preserve food? The answer is YES. This chapter describes an up-to-date review for the implantations of zeolites in several food industrial activities.

The use of natural zeolites in construction industry is presented. Zeolitic tuffs have been used for thousands of years as light – weight, durable dimension stone. Starting from the end of 20thcentury natural zeolites found large utilization in building materials: in cement manufacture, in clay – cement mixtures, in stability agents for cement manufacture, for aerated concrete production. Geopolymers are a new fire, blast and dried resistance group of building materials. Clinoptilolite tuffs can be utilized for the production of geopolymers.

Due to economic, environmental and technical benefits, one of the most widespread applications of natural zeolites is to be found in the cement and concrete industry. Application of natural zeolite in the manufacture of pozzolanic cements began from the first decades of the 20th century and shows a growing trend in recent decades. Use of natural zeolite as a supplementary cementitious material in the production of cement, mortar and concrete has been investigated in many studies. Generally, it is shown that the use of natural zeolite leads to the improvement of mechanical strength and durability properties of cement and concrete composites. In addition to pozzolanic properties, some other characteristics of natural zeolites have made them useful in special applications. This chapter aims to review the characteristics of natural zeolites and their effects on the engineering properties of cement and concrete composites.

The most N and P abundant part among the domestic waste components is the toilet wastewater; especially urine. Urine separation has been proposed to achieve maximum recovery and recirculation of nutrients in Sweden. However, storage, transportation of large amounts of urine, as well as spreading and hygienic aspects connected to handling of urine and faeces are still main obstacles in achieving full system efficiency. A decade of academic research on struvite precipitation and zeolite adsorption techniques aimed to solve some of these problems and 3 years of collaboration with Split Vision Development AB resulted in a commercially available system developed and tested in laboratory scale and in a pilot plant. One year testing of a pilot plant installed and integrated in a family house in northern Sweden is presented here. The pilot plant is based on the combined struvite precipitation and zeolite adsorption processes. The nutrient rich end-product obtained in the unit called SplitBox is vacuum-dried (fully hygienised) and this drying process connects the SplitBox to the energy system of the house for maximal energy efficiency. The pilot study shows 90 - 98 % P and 95 - 98 % N recovery from toilet wastes using urine separating toilet and SplitBox technique and a total energy saving of ca 50 % for the household after one year operation.