Didilia I. Mendoza-Castillo

Adsorption Processes for Water Treatment and Purification

This chapter covers fundamental aspects of adsorption process engineering. In particular, the importance of adsorption processes for water treatment is discussed and analyzed. Environmental impact of some key aquatic pollutants is also reviewed. Opportunity areas for adsorption process intensification are also highlighted in this chapter including a brief overview of the content of this book.

On the importance of surface chemistry and composition of Bone char for the sorption of heavy metals from aqueous solution

AbstractThis paper reports new insights on the role of the inorganic composition of Bone char (BC) on its sorption properties for the removal of heavy metals Cd2+, Ni2+, and Zn2+ ions from aqueous solution. In particular, we showed the importance of both composition and surface chemistry of BC on its sorption properties for the removal of these metal ions in aqueous solution. Results of physicochemical characterization and sorption studies suggest that the inorganic phase of BC may contribute from 60 to 92% of the sorption process of heavy metals in aqueous solution. In particular, the ion exchange process of Ca2+ involving the hydroxyapatite has an important contribution in heavy metal removal using bone char. BC is an outstanding sorbent for the removal of Ni2+ ions and appears to be suitable for water purification systems.

Tailoring the adsorption behavior of bone char for heavy metal removal from aqueous solution

This paper evaluates the pyrolysis conditions applied during the synthesis of bovine bone char and the effect of these parameters in its adsorption properties for heavy metal removal from aqueous solution at batch reactors. The synthesis route has been analyzed in detail and the surface interactions involved in the adsorption process has been studied and discussed using different characterization techniques, given a special emphasis on X-ray photoelectron spectroscopy (XPS) analysis. A proper selection of the pyrolysis conditions improved the metal uptake of bone chars by 143% where the adsorption capacities ranged from 68.3 up to 119.4 mg/g. The removal performance followed the trend Cd2+ > Zn2+ > Ni2+. However, the multicomponent removal of Zn2+, Cd2+, and Ni2+ ions in both binary and ternary mixtures was a strong antagonistic adsorption process. XPS analysis confirmed that the ion exchange between the calcium, from the hydroxyapatite structure of bone char, and the heavy metals in solution played an important role in the adsorption process. These findings are useful to enhance the efficacy of heavy metal removal from aqueous solution using bone char.

Chemical modification of Byrsonima crassifolia with citric acid for the competitive sorption of heavy metals from water

This study reports the chemical modification of the Byrsonima crassifolia biomass with citric acid to improve its sorption properties for the removal of cadmium and nickel ions from aqueous solutions under competitive sorption conditions (i.e., multicomponent solutions). The best operating conditions of the chemical modification process were identified using the signal-to-noise ratio to enhance the metal uptakes and to reduce the competitive sorption effects during the simultaneous removal of these metals using the modified biomass. Results indicated that both the sorption capacity and selectivity for heavy metal removal can be improved in multicomponent metal solutions. This improvement in sorption properties of B. crassifolia biomass is mainly related to an increment of the acidic functional groups on the biomass surface caused by the chemical reaction between citric acid and this lignocellulosic material. The methodology reported in this study can be used to increase the sorption properties of other biomasses for the effective removal of toxic pollutants from multicomponent solutions and for the synthesis of sorbents with tailored sorption properties.

Applications of activated carbons obtained from lignocellulosic materials for the wastewater treatment

Activated carbons are used in a number of industrial applications including separation and purification technologies, catalytic processes, biomedical engineering, and energy storage, among others. The extensive application of activated carbon is mainly due to its relatively lowcost with respect to other adsorbents, wide availability, high performance in adsorption processes, surface reactivity and the versatility to modify its physical and chemical properties for synthesizing adsorbents with very specific characteristics (Haro et al., 2011). In particular, the adsorption on activated carbon is the most used method for wastewater treatment because it is considered a low-cost purification process where trace amounts of several pollutants can be effectively removed from aqueous solution. Recently, the demand of activated carbons has increased significantly as a water-purifying agent to reduce the environmental risks caused by the water pollution worldwide (Altenor et al., 2009; Bello-Huitle et al., 2010).

Dynamic fuzzy neural network for simulating the fixed-bed adsorption of cadmium, nickel, and zinc on bone char

This study introduces the application of a dynamic fuzzy neural network for fitting and simulating the adsorption of nickel, cadmium, and zinc ions in mono- and bi-metallic solutions (nickel–cadmium, nickel–zinc, and cadmium–zinc) using packed-bed columns with bone char. This neural network model has shown a flexible and self-adaptive architecture with a faster learning speed than that of traditional artificial neural approaches. Results showed that this neural network model was reliable for representing the high asymmetry behavior of concentration profiles in both mono- and bi-metallic breakthrough curves where its accuracy was quite reasonable. Breakthrough parameters for mono-component and binary systems of tested heavy metals were calculated and compared. This analysis showed that the removal of these heavy metal ions in binary systems was a strong competitive adsorption process where the presence of co-ions reduced the removal performance of bone char at fixed-bed adsorbers. Results of surface characterization of adsorbent samples with X-ray photoelectron and infrared spectroscopy supported a removal mechanism based on an ion exchange between calcium from hydroxyapatite of bone char and heavy metal ions in the solution forming new metal–phosphate interactions in the adsorbent surface.

Phase Equilibrium Modeling in Non-Reactive Systems Using Harmony Search

In recent years, a significant work has been performed in the area of software development for solving global optimization problems in science and engineering applications (Floudas et al., 1999). In particular, global optimization has and continues to play a major role in the design, operation, scheduling and managing of chemical industrial processes and, according to several authors; it will remain as a major challenge for future research efforts (Floudas et al., 1999; Biegler & Grossmann, 2004; Grossmann & Biegler, 2004; Rangaiah, 2010). In the context of chemical engineering, several algorithmic and computational contributions of global optimization have been used for process optimization. As expected, finding the global optimum is more challenging than finding a local optimum and, in some applications such as the phase equilibrium modeling, the location of this global optimum is crucial because it corresponds to the correct and desirable solution (Floudas et al., 1999; Teh & Rangaiah, 2002; Wakeham & Stateva, 2004; Rangaiah, 2010). Specifically, the modeling of phase equilibrium in multicomponent systems is essential in the design, operation, optimization and control of separation schemes. The phase behavior of multicomponent systems has a significant impact in several issues of process design including the determination of the equipment and energy costs of separation and purification strategies (Wakeham & Stateva, 2004). Note that phase equilibrium calculations (PEC) are usually executed thousands of times in process simulators and, as a consequence, these calculations must be performed, reliably and efficiently, to avoid design uncertainties and erroneous conclusions about process performance. However, literature indicates that the development of reliable methods for PEC has long been a challenge and is still a research topic of continual interest in the chemical engineering community (Teh & Rangaiah, 2002; Wakeham & Stateva, 2004). Basically, PEC involve two main problems: a) phase stability analysis is used to determine if a tested system under specified operating conditions is stable or not, and b) phase split calculations are performed to establish the number and identity (i.e., composition and type) of phases existing at the equilibrium (Wakeham & Stateva, 2004). These thermodynamic calculations can be formulated as global optimization problems where the tangent plane

Adsorption of zinc ions on bone char using helical coil-packed bed columns and its mass transfer modeling

AbstractThis study reports the assessment of helical coil-packed bed columns for Zn2+ adsorption on bone char. Zn2+ adsorption breakthrough curves have been obtained using helical coil columns with different characteristics and a comparison has been conducted with respect to the results of straight fixed-bed columns. Results showed that the helical coil adsorption columns may offer an equivalent removal performance than that obtained for the traditional packed bed columns but using a compact structure. However, the coil diameter, number of turns, and feed flow appear to be crucial parameters for obtaining the best performance in this packed-bed geometry. A mass transfer model for a mobile fluid flowing through a porous media was used for fitting and predicting the Zn2+ breakthrough curves in helical coil bed columns. Results of adsorbent physicochemical characterization showed that Zn2+ adsorption on bone char can be attributed to an ion-exchange mechanism. In summary, helical coil columns appear to be a ...