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.
Keywords: Water treatment, adsorption, ion exchange, indigo carmin, acid red,
clinoptilolite, carbonized clinoptilolite, shungite, TEM analysis, SEM analysis,
Langmuir, Freundlich, BET isotherm, phenol, phosphate, nitrate, halogenide,
sulphate, Fe alginate/zeolite, hydrophobized ODA - zeolite, Slovakite, active
charcoal, lignite, perlite.
