Dynamic adsorption of 4-nitrophenol over shaped activated carbon produced from agriculture stones through microwave-assisted technique.

The aim of current work is to develop the uptake of 4-nitrophenol from the liquid phase in a dynamic system by the shaped activated carbon produced through the microwave-assisted technique. The emphasis of research is to understand the effects of production factors on the performance of adsorbents in the dynamic adsorption. Hence, the phosphoric acid ratio, microwave irradiation power, carbonization temperature, and time were changed to identify the suitable conditions for the fabrication of granular and rod-like beds from the cherry, and date stones. It was found that the stone structure and H3PO4/waste ratio significantly affect the adsorption efficiency. The proper acid/waste ratio was determined to be 1.43, and 1.80 for the activation of cherry and date stones to achieve the maximal efficiency in which the power should be fixed at the levels of 600 and 400 W respectively. The equilibrium efficiency increases with the rise in carbonization temperature and time which should be controlled exactly to reach the maximal adsorption capacity, ~ 45 mg g-1 according to the Langmuir isotherm. Owing to the high specific surface area of shaped adsorbents, 350-450 mg g-1, the fabricated beds indicated the appropriate performance for the uptake of nitrophenol due to development of micropores, < 2 nm, in the framework of activated carbon.

Treatment of tannery wastewater by silica nanoparticles produced from rice husk ash via a green route.

Rice husk, which is one of the abundant agricultural biomasses in nature, contains organic and inorganic elements, spastically silica. This waste is frequently managed via incineration, resulting in the contamination of soil, water, and air due to emission of greenhouse gasses and ash. In the present investigation, the potential of silica powder obtained from the rice husk was demonstrated by the removal of Cr(III) from the tannery wastewater. Different combinations of sulfuric, hydrochloric, and acetic acids were used as precipitation agents to produce silica through the conventional and ultrasound-assisted techniques. The mesoporous silica fabricated via the sonication indicated the larger pores, 22 nm, compared to that produced via the conventional method by the employment of sulfuric acid, 10 nm, leading to achieve an adsorption capacity ~385 mg g-1. Although both of applied techniques could develop mesoporous structure, precipitation should be carried out under sonication in the presence of acetic acid for the green production of silica with the appropriate adsorption performance. The conversion of rice husk into silica powder with specific surface area ~62 m2 g-1 could prevent the environmental pollution due to employment of acetic acid in the precipitation stage.

Management of solid waste after used motor oil recovery via production of zeolite A.

The attempt of the current study is to find an eco-friendly method for managing the solid waste deposited in the landfill of used motor oil recovery factories through the fabrication of zeolite-based compounds. This toxic waste is originated from the application of natural bentonite, traditionally used as an effective adsorbent in the recovery process. The black waste was converted to zeolite structures through the fusion technique. Firstly, the collected powder was mixed with sodium hydroxide, and boehmite followed by the thermal treatment at different temperatures, 600-800 °C. Then, the obtained precursors were hydrothermally converted to zeolite A or hydroxysodalite. The effects of processing factors like alkalinity, boehmite, and sodium aluminate ratios (respect to solid waste mass), fusion temperature, and aging time on the structural characteristics, and cation exchange capacity (CEC) were studied in detail. In order to achieve a cation exchange capacity of about 190 mg g-1, the alkali and boehmite ratios should be adjusted at 2.00 and 0.53, respectively. Based on the morphological observations, the fusion at 800 °C caused the formation of cubic particles with sharp edges. Besides, the hydrosodalite powder with the extended surface area, 77 m2 g-1, could be produced by fixing the boehmite, and sodium aluminate ratios at the levels of 0.13 and 0.40, respectively.

Industrial performance, reusability and mechanical reliability of mesoporous gamma alumina packed bed fabricated through boehmite extrusion for removal of reactive dyes from textile wastewaters.

The reusable γ-alumina packed bed was fabricated by extrusion of boehmite as rods for the removal of reactive dyes from the industrial textile wastewaters in a dynamic system. The appropriate calcination temperature, and time were determined to maximize the removal efficiency, ∼90%, in the acidic environments, pH 2-3. On the other hand, the current contribution addressed the estimation of failure probability which is a challenge for the reliable design of packed beds. Therefore, the normal, and Weibull distributions were used to evaluate the reliability of rods through Akaike information criterion (AIC), and Anderson-Darling test (ADT). The results revealed that the Weibull distribution possesses the higher accuracy in the analysis of compression strength scatter. The calcination of rods at 850 °C within 90 min not only led to fabricate a reliable packed bed with a mean strength about 860 kPa but also brought the better mesoporous structure, 8 nm, which is the main reason for the development of active sites. The thermal stability of rods provided an industrial potential for the regeneration of packed bed at 500 °C, without efficiently losing the adsorptive performance, even after reuse for ten times.

Application of solid waste of ductile cast iron industry for treatment of wastewater contaminated by reactive blue dye via appropriate nano-porous magnesium oxide.

The solid waste of ductile iron industry, which contains at least 88.0% magnesium oxide, is one of the toxic materials, leading to land contamination. On the other hand, the removal of reactive dyes from wastewaters is difficult required effective adsorbent like nano-porous MgO. The novelty of present investigation is based on nano-porous magnesium oxide production by precipitation from the solid waste to treat the wastewaters contaminated by reactive dye which is abundantly used in the textile industry. In order to improve the adsorptive properties of extracted MgO powder, the combinations of surfactants, containing cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and polyoxyethylene octyl phenyl ether (TX100) were applied based on the mixture design algorithm in the precipitation. The effects of processing factors such as surfactant composition, powder calcination temperature, surfactant dose and pH were evaluated on the removal efficiency. The results revolved that the combination of SDS and TX100, 1:1, plays an effective role in the production of particles with the appropriate average pore size, 16 nm. The adsorbent prepared in the optimum condition indicated a significant affinity for the removal of reactive dye which shows relatively pH-independent efficiency in the range of 3-9. The applied producer for fabrication of adsorbent eventually overcomes the pH-dependent problem for the toxic dye uptake, leading to produce the adsorbent with maximal adsorption capacity of 1000 mg g-1.

Efficient removal of contaminants from waste lubricant oil by nano-porous bentonite produced via microwave-assisted rapid activation: process identifications and optimization.

The low-cost Ca-bentonite was rapidly converted to a mesoporous adsorbent via microwave-assisted acidification and the obtained materials were employed for the removal of contaminants from waste lubricant oil. In order to understand the role of acid combinations on activation, the agent compositions were prepared according to the mixture design algorithm. The waste oil recovery was carried out in a batch system to determine the appropriate acid composition, optimum microwave power, radiation time, and powder/acid ratio. As power increased, the contaminant removal performance of the adsorbent was effectively raised to achieve appropriate clear base oil. The rise in power behind 600 W negatively affected the performance of the adsorbent in which the color of oil was changed from yellow to brown. The appropriate recovery of waste oil was readily achieved by employment of adsorbents in which the acidification was performed in 15 min. The microwave-assisted technique could shorten the residence time to achieve the maximum efficiency in comparison with the performance of those produced through the conventional method. Although sulfuric acid can be used for acidification of bentonite by microwave heat treatment, the combination of acetic acid, < 50 mol%, with the mentioned acid was identified as an efficient agent to improve the performance of adsorbents which is valuable from an engineering point of view.

Spectrophotometrical analysis for fabrication of pH-independent nano-sized γ-alumina by dealumination of kaolin and precipitation in the presence of surfactant composites.

The challenge with γ-Al2O3 is its pH-dependent removal efficiency and relatively low adsorption capacity in recovery of wastewaters contaminated by cationic dyes. Therefore; the objective of present investigation was to fabricate a pH-independent nano-sized alumina powder by dealumination of kaolin for uptake of dye. The dealumination of meta-kaolin was carried out by nitric acid solution and the amorphous aluminum hydroxide was precipitated with ammonia in the presence of combined surfactants containing cetyltrimethylammonium bromide (CTAB), polyethylene glycol (PEG) and polyoxyethylene octyl phenyl ether (TX100). The nano-sized gamma alumina particles were fabricated after calcination at 800 °C and then were analyzed based on spectrophotometrical method. The rod-like nano-particles with average width of 5 nm and length of 20 nm were synthesized by precipitation in the presence of admixed surfactant, CTAB-TX100, which improves the removal efficiency due to efficient modification in the interaction of particles. TX100 also showed a significant affinity for increasing the specific surface area because of ability to prevent the particle aggregation which provides a potential for synthesis of alumina adsorbent without foaming, normally observed in the presence of CTAB. Both of mentioned powders indicated relatively pH-independent removal efficiency with higher adsorption capacity. Moreover, adsorption isotherm parameters were determined to verify the improvement of removal efficiency. The presented fabrication technique eventually overcame the pH-dependent recovery problem which is feasible for the development of adsorbents because the starting material is abundant, very low energy is needed, no hazardous waste is generated and applicable in the acidic environments.

Regeneration of wastewater contaminated by cationic dye by nanoporous activated carbon produced from agriculture waste shells.

The discharge of organic dye into environment is the threat to hydrosphere and biosphere. On the other hands, the agriculture solid wastes such walnut and almond shells pose serious pollutions in lithosphere and atmosphere when burned. The aim of present investigation is to fabricate microporous activated carbon from agriculture waste shells by microwave irradiation as efficient adsorbent to overcome these problems. Firstly, zinc chloride was impregnated into milled shell particles, 300 µm, by conventional and microwave-assisted techniques and then the dry precursors were heated in the closed and open ceramic vessels in air and nitrogen atmospheres. The experimental investigation was carried out to understand the roles of different fabrication factors such as shell particle size, catalyst impregnation ratio, microwave power, carbonization temperature, and atmosphere on cationic dye removal from wastewater. The mentioned factors efficiently affect the dye removal onto obtained activated carbon. The increase in the microwave power up to 600 W could effectively increase the dye removal. However, the higher powers inversely affect the removal efficiency. The equilibrium data were well fitted by Langmuir equation with high linear regression coefficients in which the maximum adsorption capacities of activated carbon produced by walnut and almond shells were determined to be 98 and 114 mg/g, respectively. The most prominent advantage of activated carbon produced from almond shell is lower content of catalyst employed in impregnation stage. Although the larger particles of solid waste were applied, the spongy nature with average pore diameter of 2.4 nm is the unique characteristic of activated carbon fabricated from almond shell which improves the performance of adsorbent in wastewater treatment.

Management of adsorbent content in waste motor oil regeneration by spectrophotometrical study and effective acidification in production of nano-porous clay.

In the present work the application of novel technique was highlighted for reduction of adsorbent content in recovery process of waste motor oil by effective acidification. The effects of acidification factors such as acid proportions, adsorbent dose, powder/acid ratio and residence time were analyzed on removal of contaminates from waste oil. Acetic, hydrochloric and sulfuric acids were mixed according to the statistical mixture design algorithm to prepare acidification agents. The dry original clay was submitted into the prepared acidic solutions. The designed instrumental setup allowed the preparation of nano-porous powders where the controlled factors were residence time. The distillation of waste oil was carried out in the industrial scale. The significance of independent variables and their interactions were tested by blending the obtained powders with distillated oil and then the adsorption was evaluated, spectrophotometrically. The experimental results revealed the region in which the optimum regeneration of waste oil is obtainable. In order to well understand the role of nano-structured material on regeneration, the adsorbents were characterized through X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller surface area measurement and scanning electron microscopy. The employment of acetic acid in combination with sulfuric acid plays an effective role in development porous structure and improvement of contaminant adsorption. The powder produced in optimum condition contains nano-pores with diameter about 11 nm. The employment of this technique provides a potential for reduction of adsorbent content, 33.3 wt%. Finally, it was demonstrated that the efficiency of prepared adsorbent supports further development for commercial application purpose.

Optimizing adsorption of blue pigment from wastewater by nano-porous modified Na-bentonite using spectrophotometry based on response surface method.

This work highlighted the effective activation of bentonite paste to produce nano-porous powder for removal of cationic dye from wastewater. The effects of activation parameters such as soda and moisture contents, ageing time and temperature were analyzed using response surface methodology (RSM). The significance of independent variables and their interactions were tested by blending the obtained powders with wastewater and then the adsorption was evaluated, spectrophotometrically. The experiments were carried out by preparation of pastes according to response surface methodology and central composite design, which is the standard method, was used to evaluate the effects and interactions of four factors on the treatment efficiency. RSM was demonstrated as an appropriate approach for optimization of alkali activation. The optimal conditions obtained from the desirable responses were 5.0wt% soda and 45.0wt% moisture, respectively in which the powder activation was carried out at 150°C. In order to well understand the role of nano-structured material on dye removal, the adsorbents were characterized through X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and Brunauer-Emmett-Teller surface area measurement. Finally, the analysis clearly demonstrates that the dye removal onto prepared adsorbent is well fitted with Langmuir isotherm compared to the other isotherm models. The low cost of material and facile process support the further development for commercial application purpose.