Search

Porous asphalt (PA) is an open-graded hot mixed asphalt that presents improved surface drainage during rainfall, improving road safety in wet weather and preventing rainfall water from receding in closed areas. The main challenge facing PA paving is binder draindown during mix transportation and placement due to the confluence of low fillers cases, open-graded aggregate gradation, and high asphalt contents. Mineral fibers such as slag wool (SW), despite their negative effects on human health and the environment, have been used as stabilizers in PA mixtures to increase binder retention and avoid stability reduction. This study evaluates using human scalp hair (HSH) as an alternative stabilizing fiber to SW in PA mixtures. Using HSH in PA mixtures is a sustainable waste recycling method and an economical solution to enhance the binder retention and stability of PA mixtures. The performance of the PA mixtures that stabilized with SW (control) and HSH was compared with National Asphalt Pavement Association (NAPA) requirements. The fiber length of 1–5 mm was maintained for SW and HSH. The PA standard gradation suggested by NAPA was used to form the stone matrix of the investigated PA mixtures. The Marshall design method was used to obtain the optimum asphalt and stabilizer contents. The performance evaluation tests were performed on SW and HSH mixtures, including loss of stability, moisture sensitivity, draindown, cantabro abrasion and rutting depth. Based on the results of the performance evaluation tests, the PA mixtures stabilized by HSH show a convergent performance compared with those stabilized by SW. The findings indicated that HSH can be considered an adequate stabilizer for PA mixtures instead of SW fibers.

Lignocellulosic fibers, which obtained from Citrus trees trimmings, were modified with Aspergillus flavus (EGYPTA5) enzymes. The non-modified and the modified lignocellulosic fibers were used with low density polyethylene (LDPE) by melt blending brabender method at 170 °C with different ratio (5, 10 and 20 wt%) to obtain wood plastic composites (WPC). The prepared samples were characterized using Fourier-transformed infrared (FT-IR), Scan Electron Microscope (SEM), and Water vapor transmission rate (WVTR) as well as, the mechanical, thermal, biodegradability and swelling properties were examined. The fabricated WPC displayed good mechanical and thermal properties compare with pure LDPE. Also, the WVTR was enhanced by the addition of modified lignocellulosic fibers over the unmodified one. Moreover, the enzymes assay such as cellulase and lignin peroxidase enzymes were estimated and confirming the growing of fungi on the lignocellulosic fiber in solid state fermentation condition to improve lignin peroxidase production and eliminate cellulose enzymes. The fabricated WPC can be used in different environmental application such as packaging system, that it will be green, economic, and partially biodegradable.

Polyaniline nanocomposites were prepared via in situ emulsion polymerization in the presence of Na+ montmorillonite (Na+MMT). For achieving this purpose the clay was organophilized to (MMT-CTA) form using cetyltrimethyl ammonium bromide (CTAB). The X-ray diffraction (XRD) demonstrated that the basal space of Na+-montmorillonite increased after the organophilization from 11.21 to 19.35 Å. Polyaniline/montmorillonite (PAn/MMT) nanocomposites were prepared by intercalating the emulsion of aniline monomer with treated organically layers of (Na+-MMT) using ammonium peroxydisulfate (APS) as an initiator. Furthermore aniline hydrochloride (AnHCl) was used as a modifier and monomer to prepare PAn/H+MMT nanocomposites by cation exchange of the anilinuim moiety with the sodium ion inside the basal spaces which enlarged after the polymerization process to 35 Å as evidenced from X-ray diffraction (XRD). The d-spacing of the PAn/H+-MMT nanocomposite was found to become wider about 23.79 Å than that of the pure Na+-MMT, and successful intercalation or exfoliation of PAnH+ into Na+-MMT layers. The prepared PAn/MMT nanocomposites were characterized by thermal gravimetric analysis (TGA), scanning electron microscope (SEM), and transmission electron microscope (TEM). The electrical property measurements showed an enhancement in the conductivity values of the prepared nanocomposites especially on using AnHCl monomer to be in the order of 10−1 S/cm.

Alumina gels AN6 and AN7 were prepared by precipitation with NaOH from hydrated aluminum sulfate at pH 6 and 7, respectively. A third alumina gel AA7 was similarly prepared, but by precipitation with 30% ammonia. Pure cadmia C8 and C9 were precipitated from cadmium sulfate at pH 8 and 9 using NaOH. Five mechanically mixed gels ACM (1:0.25), ACM (1:0.5), ACM (1:1), ACM (0.5:1) and ACM (0.25:1) were prepared by thoroughly mixing the appropriate molar ratios of AN7 and C8. Also, five coprecipitated gels ACC (1:0.25), ACC (1:0.5), ACC (1:1), ACC (0.5:1) and ACC (0.25:1) were coprecipitated by dropping simultaneously the appropriate volumes of 1 M aluminum sulfate, 1 M cadmium sulfate and 3 M NaOH. Calcination products at 400, 500, 600, 800 and 1000 °C were obtained from each preparation. TG–DTA patterns of uncalcined samples were analyzed and the XRD of all 1000 °C-products and some selected samples calcined at 400–800 °C were investigated. The thermal behaviors of pure and mixed gels depend on the precipitating agent, pH of precipitation, chemical composition and method of preparation. Generally, calcination at temperatures below 800 °C gave poorly crystalline phases. Well crystalline phases are obtained at 800 and 1000 °C. For pure alumina γ-Al2O3 was shown as 400 °C-calcination product that transforms into the δ form around 900 °C and later to θ-Al2O3 as a major phase and α-Al2O3 as a minor phase at 1000 °C. CdO was shown by 500 °C-calcined cadmia gel that showed color changes with rise of calcination temperature. The most stable black cadmium oxide phase (Monteponite) is obtained upon calcination at 1000 °C. Thousand degree celsius- calcined mixed oxides showed θ-Al2O3, α-Al2O3, CdAl2O4 and monteponite which dominate depending on the chemical composition.

We obtain in this paper the expressions of solutions of the following class of difference equations xn+1=xn-2k+1±1±Πi=1kxn-2i+1,n=0,1,2,… with conditions posed on the initial values x−j, j = 0, 1, 2, … , 2k − 1, where k ∈ {1, 2, …}.

A Co 3 O 4 /Al 2 O 3 catalyst containing 0.20 mol% Co 3 O 4 and an Ag 2 O/Al 2 O 3 catalyst containing 0.2 mol% Ag 2 O were prepared using the impregnation method. Co 3 O 4 –Ag 2 O/Al 2 O 3 samples containing 0.2 mol% Co 3 O 4 and varying small molar percentages of Ag 2 O were also prepared. Portions from the catalysts thus obtained were calcined at 773, 973 and 1173 K. The textural properties of the catalysts were determined from the adsorption of N 2 at 77 K, while their structural properties were investigated using TG, DTA, XRD and TPR techniques. The surface acidities of the catalysts were determined via titration with n-butylamine in a non-aqueous medium. The conversion of propan-2-ol at 573 K was followed using the micro-catalytic pulse technique, whereas the decomposition of H 2 O 2 at 298–313 K was followed by determining the volume of oxygen released with time. Solid-solid interactions between the components of the systems resulted in the formation of Co 3 O 4 and CoAl 2 O 4 , their ratio depending on the chemical composition and heat-treatment temperature employed with Ag in its metallic form. The textural properties of the investigated catalysts also depended on the chemical composition and calcination temperature. The surface acidity of the catalysts is an important factor in determining their catalytic activity towards the conversion of propan-2-ol whereas the redox-reactive ion-pairs formed between Ag and Co determine their activity towards H 2 O 2 decomposition.

Vanadia/titania catalysts were prepared containing 6.0 or 8.0 wt% V 2 O 5 via the impregnation method. The samples as prepared were calcined at 400°C or 600°C, respectively. Selective catalytic reduction (SCR) of NO with NH 3 was carried out at 257°C over the prepared catalysts. NO conversion as a function of time was followed and the stationary conversion versus the amount of catalyst employed was also investigated. It was found that the vanadia/titania catalysts calcined at 400°C were more active in the SCR of NO with NH 3 relative to those calcined at 600°C. This was attributed to such catalysts possessing complete monolayer coverage of vanadia on the titania substrate. It was established that V 5+ was not the active vanadia species but V 4+ and V 3+ may act as such for the SCR of NO with NH 3 .

Titania samples were prepared by precipitation at pH 3.0 (to provide ‘T a ’ samples) or at pH 9.0 (to provide ‘T b ’ samples). These materials were then impregnated with NH 4 VO 3 to obtain vanadia/titania catalysts of different V 2 O 5 content. These V 2 O 5 /TiO 2 samples were subsequently calcined at 400°C or 600°C to obtain two series. The oxidation of o -xylene was undertaken at 250°C, 300°C or 350°C using a conventional flow apparatus at atmospheric pressure. The reaction products were detected and separated via a gas chromatograph fitted with a flame ionization detector. The chemical composition of the catalyst, the calcination temperature, the reaction mixture employed and the reaction temperature were among the variables considered. Catalysts calcined at 400°C were more active than those calcined at 600°C, thereby indicating that anatase was the proper titania phase for supporting oxidation catalysts. Titania samples precipitated at pH 3.0 were more effective as a support for vanadia than those precipitated at pH 9.0 despite the fact that they possessed lower surface areas. This demonstrated that surface area was not a determining factor in catalyst performance. The conversion of o -xylene to phthalic anhydride increased with increasing vanadia content in the catalysts employed and with increasing reaction temperature. Surface acidity was one factor amongst others contributing to the catalytic activity. It is thought that acid sites enhance the reduction of V 5+ to lower oxidation states to provide the active oxidation sites. Mechanisms for the partial oxidation of o -xylene were advanced and explained.

FT-IR spectral studies of titania calcined at 400°C or 600°C indicated the presence of four important absorption bands with maxima located at 1630, 2920, 3670 and 3740 cm −1 , respectively. These absorption bands have been ascribed to undissociated, coordinated water, hydrogen-bonded OH, acidic OH and basic OH groups, respectively. For vanadia/titania samples containing 6 wt% and 12 wt% V 2 O 5 calcined at 400°C or 600°C, the band at 1630 cm −1 still existed in the corresponding spectra whereas that at 2920 cm −1 disappeared, thereby indicating an interaction between the vanadia and the hydrogen-bonded OH groups. The FT-IR spectra of pyridine adsorbed on to titania or titania/vanadia samples exhibited bands at 1420 cm −1 and 1540 cm −1 , respectively, the former being ascribed to Lewis acidity and exhibiting a shift to lower wavenumbers with increasing vanadia content, while the latter was ascribed to the presence of Brönsted acid sites. Temperature programmed desorption (TPD) of pyridine from titania exhibited three desorption peaks extending over the temperature ranges 267–288°C, 335–370°C and 480–510°C, respectively. Impregnation of the initial titania samples with vanadia led to an increase in both the amount of acid sites present on the surfaces of the samples and in the acid strength. Besides reacting with Brönsted and Lewis acid sites, pyridine also underwent hydrogen bonding, with the hydrogen atom serving as a bridge between two electronegative nitrogen atoms.

Titania gels, T a and T b , were precipitated from aqueous solutions of titanium tetrachloride at pH values of 3.0 and 9.0, respectively. Calcination products were obtained from these gels by thermal treatment at 300–1000°C. Vanadia/titania catalysts were obtained by impregnating T a and T b with ammonium vanadate to give products containing 4–12 wt% V 2 O 5 . These products were calcined at 400°C or 600°C, respectively. The adsorption of nitrogen at −196°C was followed and the isotherms thus obtained analyzed to enable the determination of the textural characteristics of the catalysts through the use of conventional methods of textural analysis. The specific surface area and total pore volume of titania decreased and its mean pore radius increased on increasing the calcination temperature from 400°C to 1000°C. Titania precipitated at pH 3.0 and calcined at 1000°C exhibited non-porous characteristics as indicated by the absence of hysteresis in the corresponding adsorption isotherm. The textural changes were attributed to the anatase → rutile transformation and also to the sintering of rutile. The specific surface area and porosity of vanadia/titania catalysts changed with increasing calcination temperature and with increasing vanadia content. However, the effect of calcination temperature was more pronounced.

Activated carbons were prepared by activation of cherry and wild cherry stones with phosphoric acid and zinc chloride. The adsorption of nitrogen at −196°C and of carbon dioxide at 0°C was followed and the data obtained analyzed through the use of models based on theories of surface coverage and micropore filling. Chemically-activated carbons obtained from cherry and wild cherry stones exhibited high surface areas and large total pore volumes. Most of the pores lay in the micropore region while a small fraction of the total surface area was located in non-micropores. Fair agreement was established on comparing the textural parameters derived from models based on the theory of surface coverage with those derived from the micropore filling theory. Micropores should be classified into ultrafine pores, micropores and super-micropores, such sub-division helping in the prediction of the adsorption behaviour and in the interpretation of the data derived therefrom.

Titania gels T a and T b were precipitated from TiCl 4 at pH 3.0 and 9.0, respectively, using ammonia solution. Calcination products were obtained by the thermal treatment of the gels at 300, 400, 600, 750 and 1000°C, respectively. Thermal analysis, X-ray diffraction and FT-IR spectroscopy demonstrated that the anatase → rutile transformation commenced when T a was calcined at 400°C, with the rutile form predominating when calcination was conducted at 600°C. Calcination at 750°C or 1000°C was associated with complete anatase → rutile conversion. The calcination product of T b at 400°C was pure anatase, transformation to rutile taking place above this temperature and predominating at 600°C. Rutile was the sole phase present when T b was calcined at 750°C. Vanadia/titania catalysts were obtained by impregnating T a and T b with an aqueous solution of NH 4 VO 4 of concentration sufficient to obtain samples containing 4.0, 6.0, 8.0 or 12.0 wt% V 2 O 5 . The calcination products at 400°C and 600°C were characterized by thermal analysis, X-ray diffraction, FT-IR spectroscopy, electronic spectral analysis and magnetic susceptibility measurements. The presence of vanadium enhanced the anatase → rutile transformation. The measured X-ray diffraction lines and FT-IR peaks indicated the existence of vanadium as a separate oxide, mainly V 2 O 5 . However, the electronic spectra and magnetic susceptibility measurements predicted the possible existence of a V 4+ species.

Ternary vanadia–chromia/silica, molybdena–chromia/silica and nickel oxide–chromia/silica solid catalysts were prepared by the impregnation method. Their structural characteristics were examined using differential thermal analysis (DTA) and X-ray diffraction techniques. The catalytic activities of the prepared samples towards the conversion of isopropanol and cyclohexanol and the kinetics of these catalytic conversions were studied with the aid of a microcatalytic pulse technique. In addition, the surface acidities of selected samples were measured from the percentage of propene produced by the poisoned catalysts. X-Ray diffraction and differential thermal analysis revealed that the only detectable phase was α-Cr 2 O 3 with the presence of all other phases or spinel not being confirmed. The order of the surface acidities was found to lie in the sample sequence: 3 wt% V 2 O 5 –20 wt% Cr 2 O 3 /SiO 2 > 3 wt% MoO 3 –20 wt% Cr 2 O 3 /SiO 2 > 20 wt% Cr 2 O 3 /SiO 2 > 3 wt% NiO-20 wt% Cr 2 O 3 /SiO 2 , all samples having been precalcined at 500°C. Catalytic conversion of isopropanol gave propene and acetone, whereas cyclohexene, cyclohexanone and methylcyclopentene (as an isomerization product) were produced from the catalytic conversion of cyclohexanol. The catalytic activity was found to be influenced considerably by the type of impregnating ion employed and by the precalcination temperature, and hence by the surface acidity of the examined catalysts. On the other hand, the Bassett–Habgood and Kiperman equations could be applied in a satisfactory manner to the generation of the various reaction products. The calculated activation energies for the catalytic conversion of isopropanol and cyclohexanol were compared.

Chemically activated carbons were obtained from olive stones either by carbonization with H 3 PO 4 at 300–600°C or by carbonization with ZnCl 2 at 600°C. Nitrogen adsorption at 77 K was determined for all the activated carbons. The adsorption data were interpreted by considering some conventional adsorption models. Maximum activation with H 3 PO 4 occurred at 450°C. However, the adsorption capacities of the ZnCl 2 -activated carbons were far higher than those of carbons activated with H 3 PO 4 . Carbons activated with H 3 PO 4 or ZnCl 2 are mainly microporous with the non-micropores representing a small fraction of the total porosity. Although, the nitrogen isotherms are Langmuirian in shape, application of the Langmuir equation led to large monolayer capacities of uncertain confidence. The surface areas and micropore volumes determined by the application of the t-method of de Boer and the α S -method of Sing were comparable and were slightly higher than those determined by the application of the DR model based on micropore filling. The t-method and the α S -method are complementary to each other and would seem to give confident values because they are based on standard reference non-porous materials. The micropore region may be sub-divided into two sub-regions distinguished by the different filling mechanisms involved.

Activated carbons were prepared from olive stones either by the addition of zinc chloride (25–50 wt%) or by gasifying non-activated carbon with steam to burn-offs between 25% and 49%. The adsorption of nitrogen at 77 K was investigated and the adsorption data interpreted by the application of the Langmuir equation, the BET equation and the α S -method. The adsorption of carbon dioxide at 273 K was also followed and the data analyzed using the DR and DA equations. The adsorption of iodine from aqueous potassium iodide solution, and of Methylene Blue and p -nitrophenol from aqueous solutions at 298 K was also determined. Activation with zinc chloride produced physical and chemical changes which modified the thermal degradation process. Carbonization with zinc chloride restricted the formation of tars with the subsequent formation of solid carbon, the amount of zinc chloride incorporated in the precursor governing the porosity of the resulting carbon. The atmosphere under which activation of samples containing zinc chloride was undertaken was another factor in determining the texture of the carbon. Activation with steam to low burn-offs created new micropores by burning off the more reactive carbon atoms, but at high burn-offs erosion of the pore walls occurred leading to pore widening. Adsorption from solution was determined by the solubility of the solute in the solvent and by competition for this solute between the solvent and the adsorbent. The pore size of the carbon adsorbent and the molecular size of the adsorbate molecule were prominent factors in determining the extent of adsorption from solution.

Activated carbons were prepared by carbonizing ground apricot stones impregnated with 20–60 wt% phosphoric acid at 300–600°C, in a limited air supply. Highly activated carbons with surface areas amounting to 1200 m 2 /g and pore radii of 8–10 Å were obtained when a mixture of apricot stones and 50 wt% phosphoric acid was carbonized at 450°C. Activation with phosphoric acid proceeds via the creation of pores of radii between 8 Å and 10 Å. The adsorption data for nitrogen at 77 K obey models based on surface coverage satisfactorily and also models based on pore volume filling. Although a slight upward deviation was shown in the Dubinin–Radushkevich (DR) plots, this model was still verified and allowed the determination of useful sorption parameters.

Different aluminas were prepared through the precipitation of aluminium hydroxide in the absence and presence of various surfactants, followed by calcination at different temperatures. Examples of anionic and cationic surfactants employed were sodium dioctylsulphosuccinate (AOT) and dodecylamine hydrochloride (DAH), respectively. The surface properties of the samples obtained were evaluated through measurements of their BET surface areas using nitrogen adsorption at 77 K and the adsorption of Methyl Orange from aqueous solution at 30°C. The addition of cationic surfactant during the precipitation process produced alumina with a high surface area, whereas only a limited change in the surface properties was induced by the anionic surfactant.

The adsorption of low molecular weight poly(methacrylic acid n-butyl ester) (PBMA) and poly(ethylene glycol) (PEG) on silicas precalcined at 673–1473 K was studied. The changes brought about in the textural properties (total surface area and pore volume distribution) by the adsorption of these polymers were determined. Adsorption of PBMA and PEG resulted in a decrease in the specific surface area as determined by nitrogen adsorption at 77 K since the fraction of the surface located in the micropores was covered by the polymer. Adsorption of polymers reduced the water adsorption capacities of the silicas, particularly those precalcined at ≤ 1073 K, as a result of a decrease in the number of surface OH groups. Polymer adsorption on the precalcined silicas made the contribution of mesopores more prominent, the changes in the textural properties of the silicas depending on the stage at which the polymer was added during the course of silica preparation.

A range of NiO/Al 2 O 3 , solids (4.0–12.0 wt% Ni) was prepared by the impregnation technique. The textural properties of these solids were determined from nitrogen adsorption measurements at 77 K. Reduction of the solids with hydrogen was carried out 650, 675, 700 and 725 K. Some catalytic parameters for these reduced materials were determined from studies of the adsorption of hydrogen at 400 K. The methanation of carbon monoxide over these reduced materials used as catalysts was followed between 550 K and 600 K using a steady-state flow reactor. The surface area of the NiO/Al 2 O 3 solids decreased and their mean pore radius increased with increasing content of NiO. Increasing the temperature employed for their reduction led to increased diffusion of Ni atoms to the surface with a consequent increase in their catalytic activity. A direct relationship was found between % methanation and the surface area of the reduced catalytic material expressed as m 2 /g (catalyst).

Four chromia/silica samples containing 5–30 wt% Cr III were prepared by impregnation methods and calcined at 773–1173 K. Nickel, molybdenum and vanadium oxide-impregnated Cr 2 O 3 /SiO 2 samples were also prepared by impregnation and were subjected to the same thermal treatment. The textural parameters of all the samples prepared were determined from the adsorption of nitrogen at 77 K, while X-ray diffraction (XRD) and differential thermal analysis (DTA) techniques were used to elucidate their structures. The catalytic properties of the solids so prepared in the catalytic cracking of cumene were investigated using a pulse microcatalytic technique. The surface areas evaluated for the various Cr 2 O 3 /SiO 2 samples studied were found to decrease gradually on increasing their Cr III content, the calcination temperature and on addition of Ni, Mo and V oxides. DTA and XRD studies demonstrated the absence of any interaction between the SiO 2 and Cr 2 O 3 , with the latter being the only phase capable of detection by these techniques. Samples impregnated with Ni, Mo and V ions also showed no interaction between these ions and Cr 2 O 3 and SiO 2 , with only the corresponding oxides being detected. The results obtained for the catalysis studies also indicated that the cracking of cumene depended on the metal content, impregnant cations and thermal treatment of the solids employed.

Zinc chloride-activated carbons and steam-activated carbons were prepared from Maghara coal. The textural properties were determined from low-temperature nitrogen adsorption. Zinc chloride activation is usually associated with the creation of new micropores while steam activation involves pore widening particularly when the percentage burn-off is high. The adsorption of SO 2 on steam-activated carbon is high compared with ZnCl 2 -activated carbons. Steam activation develops surface basic groups which provide chemisorption sites for SO 2 . The adsorption of SO 2 is enhanced in the presence of O 2 and water vapour and involves the formation of sulphuric acid in this case. Sulphur dioxide adsorption is related to the chemistry of the carbon surface rather than to the extent of the surface area of the activated carbon.

A series of activated carbons ‘Z’ was prepared from Aleppo Pistacia Vera shells using different percentages of zinc chloride at 873 K in the absence of air. Another series ‘ZN’ was prepared using the same conditions as for the ‘Z’ series but employing a nitrogen atmosphere to effect carbonization. The textural properties of the two series of samples were determined from the adsorption of carbon dioxide and methylene blue at 298 K. Activated carbons with a high adsorptive capacity for methylene blue were obtained. Activation with zinc chloride proceeded with increasing microporosity via the creation of new micropores. At high percentages of zinc chloride, slight partial pore widening may take place. Carbon dioxide was accessible to the entire pore system and was therefore suitable as a probe for the investigation of the textural properties of the activated carbons studied. A fraction of the porosity was inaccessible to methylene blue molecules and consequently lower surface areas were calculated from the adsorption of this dye molecule.

Co-precipitated SnO 2 –Cr 2 O 3 catalysts of different chemical composition were prepared. The textural properties were determined from the low-temperature nitrogen adsorption isotherms while the structural properties were determined using FT-IR spectroscopic techniques. The magnetic moments of the catalysts were measured by the Gouy method. Catalytic conversion of 2-propanol, 1-butanol and the dehydrogenation of cyclohexane were followed using the pulse microcatalytic technique. No spinel structure was detected, even upon calcination at temperatures as high as 973 K. Only Cr 2 O 3 was detected for samples containing ≥15 mol% chromia. The chemical composition and calcination temperatures are important factors in determining the textural properties of mixed oxide catalysts. The catalytic activity depends on the effective magnetic moment and surface acidity.

Non-activated carbon ‘A’, physically-activated carbons P1–P4, zinc chloride-activated carbons Z1–Z4 and potassium sulphide-activated carbons K1–K4 were prepared from Maghara coal (Sinai, Egypt). The surface areas of these carbons were determined by investigating the adsorption of carbon dioxide at 298 K and of nitrogen at 77 K. The decolourization powers of the carbons were determined from methylene blue adsorption at 308 K. The adsorption of methanol, benzene, n-hexane, n-octane and α-pinene at 308 K was also determined using equilibrium and flow techniques. The removal of ammonia and phenol from water was investigated on some selected samples. The activated carbons showed high capacities towards the removal of organic pollutants from water and from gas streams via adsorption. Their capacity towards a particular pollutant depends on the method of activation and is related to the textural and/or the chemistry of the carbon surface.

CuO/Fe 2 O 3 (1:1) was prepared by co-precipitation. Six thermal products (I–VI) were obtained by calcination in the temperature range 300–800°C. The structures of I–VI were determined from XRD patterns and they were also identified from electrical conductivity measurements in the temperature range 313–523 K. The textural properties were determined from nitrogen adsorption at 77 K and the acidities of the thermal product were measured by pyridine chemisorption at 423 K. The decomposition of H 2 O 2 over the catalysts I–VI was followed in the temperature range 303–323 K. Conversion of 2-propanol was investigated at 523 K. Calcination of CuO/Fe 2 O 3 at 600°C resulted in partial transformation to CuFe 2 O 4 , this transformation predominating at 700°C and being complete at 800°C. Two mechanisms of electrical conduction are involved for catalysts calcined at 600–800°C depending on the temperature at which σ is measured. The surface area decreases and the average pore radius increases with increasing calcination temperature due to sintering and spinel formation. A mechanism is suggested for H 2 O 2 decomposition and the activity and selectivity of the catalysts towards the conversion of 2-propanol are discussed.

Five calcination products AI–AV were obtained by the calcination of alumina gel in the temperature range 673–1473 K. The adsorption of nitrogen at 77 K on these products was determined volumetrically. The chemisorption of H 2 , CO, CO 2 and CH 4 at 300, 320 and 340 K was also determined for each alumina sample. Increasing calcination temperature caused phase changes with formation of the most stable phase α-Al 2 O 3 starting at 1273 K and predominating at 1473 K. Chemisorption depends on the nature of the adsorbent and the adsorbate molecules. The amount adsorbed was related to the critical temperature of the gas involved while the heat of adsorption was related to the strength of the interaction between the adsorbent and the adsorbate. The polarizability of the adsorbed gas molecule is a determining factor in its chemisorption, particularly on polar surfaces.

The textural properties of non-irradiated and γ-irradiated Ni/Al 2 O 3 and Co/Al 2 O 3 systems with different chemical compositions were determined from the adsorption of nitrogen at 77 K. Chemisorption of hydrogen at 320 K and hydrogenation of benzene at 400 K were studied on the reduced catalysts. The surface areas of γ-irradiated catalysts are higher than those of their non-irradiated equivalents. γ-Irradiation also increases the hydrogen uptake, the metallic surface area and the percentage dispersion of the metal on the support. The hydrogenation activity also increases upon irradiation with γ-rays. All these changes are more pronounced in catalysts with a high metal loading.

Zinc chloride-activated and steam-activated carbons were prepared from Maghara coal (Sinai, Egypt). The surface properties of these carbons were determined from nitrogen adsorption isotherm studies at 77 K and of carbon dioxide at 298 K. The adsorption of Methylene Blue from aqueous solution at 308 K was also investigated. The removal of heavy metals (Hg 2+ , Cd 2+ and Pb 2+ ) from aqueous solution was investigated at pH < 7.0 and at 308 K. The prepared activated carbons exhibited high adsorption capacities for Methylene Blue. The maximum capacity amounted to 83 mg dye per g of carbon, which is equivalent to a surface area of 500 m 2 /g. The capacity for the removal of heavy metals from their aqueous solutions depends on the pH and the extent of activation, i.e., on the amount of zinc chloride used for chemical activation or on the percentage burn-off during physical activation with steam.

Catalysts of the type CuO/Al 2 O 3 , NiO/Al 2 O 3 and Co 3 O 4 /Al 2 O 3 with different chemical compositions and subjected to different calcination temperatures were prepared using the impregnation technique. The crystal structure of the calcination products was determined by X-ray diffraction (XRD) while the textural properties were determined from nitrogen adsorption at 77 K. The activity of the catalysts towards the oxidation of carbon monoxide with O 2 at different temperatures was also investigated. XRD indicated that calcination of these systems at ≤1073 K did not lead to the formation of spinel. Moreover, no characteristic lines indicating the existence of any metal oxide were observed when the concentration of the latter was less than 10 mol%. The catalytic oxidation of CO followed first-order kinetics with the catalytic activity depending on the metal oxide loading and its dispersion on the surface of the alumina. In most cases, Co 3 O 4 /Al 2 O 3 catalysts exhibited the highest activity.

CuO–AlPO 4 samples containing varying amounts of CuO were prepared at 25°C. The catalysts were obtained by thermal treatment, in air, at 500°C. The textural properties of the catalysts were determined from nitrogen adsorption measurements at –196°C. The surface acidity was determined by a calorimetric method. The conversion of isopropanol was measured on CuO–AlPO 4 samples using microcatalytic techniques. An enormous change in the textural properties was found as a result of the effect of CuO on the structure of AlPO 4 . The surface acidity decreased with increasing CuO content. The catalytic dehydration of isopropanol is related to the surface acidity while dehydrogenation of the alcohol depends on the CuO content.

The textural properties (surface area and porosity) of activated carbons change upon treatment with oxidizing solutions. The extent of this change is related to the strength of the oxidizing agent. Oxidation also changes the chemistry of the surface by forming carbon–oxygen groups which are the sites upon which the initial adsorption of water vapour takes place. The adsorption of water vapour at 300–320 K is mainly physical and the isosteric heat of adsorption decreases continuously as the surface coverage increases. The entropy of adsorption of water vapour on untreated and oxidized carbons, at different adsorption temperatures, has been calculated.

A technical silica gel was impregnated with a solution of the titled heteropoly acid (1–20 w/w%) and calcined at 400, 600 or 800 °C. Dehydration of the alcohol generally increased with the loaded acid, and decreased almost linearly with the reaction temperature (360–260°C). The best alcohol decomposition was achieved over the 600°C-calcined catalysts when over 90% conversion to propene was attained. The apparent activation energies decreased with the degree of loading and attained a value of 22 kJ/mol on the 600°C-calcined 20% HPMo-supported catalyst (half that on the solids calcined at 400°C and 800°C). The catalytic dehydration cannot be described by means of a proton-involved mechanism on the severely treated catalysts at ≥600°C. An outer surface mechanism might be effective involving terminal oxygens and MoV ions.

Samples of nickel on alumina (1.1–10.4 wt.% Ni) were prepared by impregnating alumina in hydrated nickel nitrate. The textural properties of the calcined catalysts have been determined from nitrogen adsorption at 77 K. Calcined catalysts were reduced prior to determination of the chemisorbed benzene at 308 K or chemisorbed hydrogen at 383 K. Hydrogenation of benzene was also determined at 473 K using the flow technique. The surface area of NiO/Al 2 O 3 catalysts decrease and their mean pore radii increase with an increase in NiO content. These changes are more pronounced for catalysts containing more than 5% metal. Chemisorption of benzene proceeds via the formation of π-bonds with nickel. The chemisorption of hydrogen indicated that the percentage dispersion decreases and the crystallite size increases with an increase in metal loading. Dispersion, crystallite size and metal surface are important factors in determining the activity of supported nickel catalysts for benzene hydrogenation.

Pure alumina, CuO/Al 2 O 3 and ZnO/Al 2 O 3 have been calcined in the temperature range 500–1000°C and the phase changes involved followed using DTA and XRD techniques. The surface properties of all the calcination products were determined from the adsorption of nitrogen at 77 K and the chemisorption of pyridine at 423 K. The catalytic conversion of isopropanol on all the thermal products was also investigated. The surface areas of CuO/Al 2 O 3 and ZnO/Al 2 O 3 decreased while the pore radii increased with increasing calcination temperature from 500°C to 1000°C. CuAl 2 O 4 forms above 800°C while ZnAl 2 O 4 crystallizes at 600°C The acidity of the surface decreased when the calcination temperature was increased above 500°C. The conversion of isopropanol proceeds via dehydration of the alumina catalysts. CuO/Al 2 O 3 and ZnO/Al 2 O 3 surfaces catalyze both the dehydration and dehydrogenation of this alcohol.

Non-activated carbon has been prepared by carbonizing waste products manufactured from phenol formaldehyde at 1073 K in a nitrogen atmosphere. Activated carbons were obtained by gasifying the non-activated product with air at 673 K, or with steam at 1173 K, to different levels of burn-off. The adsorption of nitrogen at 77 K and of carbon dioxide at 298 K was measured for all the carbons prepared using volumetric apparatus. The adsorption of iso-octane and α-pinene at 320 K was carried out gravimetrically using silica spring balances. The adsorption of methylene blue and of phenol from their aqueous solutions was determined spectrophotometrically. The adsorption of ammonia from its aqueous solution at 308 K was determined colorimetrically. The surface area of the activated carbons increased with increasing percentage burn-off to reach a maximum and then decreased with further increase in percentage burn-off. Gasification with oxidizing gases changed the porosity of the carbon with the change depending on the extent of gasification. The adsorption of iso-octane and α-pinene increased with increasing percentage burn-off as a result of pore widening. The low burn-off carbons obtained from phenol formaldehyde wastes are characterized by extremely high surface areas and microporosity, and a high CO/CO 2 ratio on outgassing. The carbons exhibit high phenol adsorption capacities. Ammonia adsorption is favoured on carbons of a low CO/CO 2 ratio.