Wastewater treatment adsorption capacity

In addition to anionic species, some metal cations can also be removed via adsorption processes with LDH materials. Recently, Lazaridis reported an interesting removal of two anions (P04 , SCN ) and three cations (Cd , Pb ", Ni " ) from aqueous solutions in single batch systems using uncalcined and calcined (773 K) Mg/Al LDH carbonate materials [148]. It was found that the calcined material showed higher sorption capacities than the uncalcined material for all the ions. Since the sorption capacities are relatively high, the author suggested that LDHs could be considered as a potential materials for sorption of both anions and cations in wastewater treatment systems. Seida et al. have also reported the rapid removal of dilute Pb from dilute aqueous solutions by a column packed with a pyroaurite-like Mg/Fe-COs LDH compound over a wide range of space velocity (Sv = 150-800 min" ) [149]. 

The adsorption capacity of activated carbon may be determined by the use of an adsorption isotherm. The adsorption isotherm is an equation relating the amount of solute adsorbed onto the solid and the equilibrium concentration of the solute in solution at a given temperature. The following are isotherms that have been developed Freundlich Langmuir and Brunauer, Emmet, and Teller (BET). The most commonly used isotherm for the application of activated carbon in water and wastewater treatment are the Ereundlich and Langmuir isotherms. The Freundlich isotherm is an empirical equation the Langmuir isotherm has a rational basis as will be shown below. The respective isotherms are ... 

In conclusion, we have demonstrated the unusual adsorption behaviors of microporous titanosilicate ETS-10 towards heavy metal ions with an extremely t rate and in a large adsorption capacity, showing the application potentials of ETS-10 for water and wastewater treatment. The adsorption is most likely via ion exchange. It is believed diat die unique compositional frameworic together with the large pore size of ETS-10 play a vital role in determining its remaricable adsorption properties towards heavy metal ions. 

The present stu(fy shows that the coir pith carbon is an effective adsorbent for the removal of methylene blue from aqueous solution. Adsorption follows Langmuir isotherm. Kinetic data follow second order kinetic model. The adsorption capacity was found to be 5.87mg/g. The results would be useful for the fabrication and designing of wastewater treatment plants for the removal of dye. As the raw material, coir pith is discarded as waste in coir industries, the treatment method using coir pith carbon is expected to be economical. 

On the basis of monitoring the adsorption characteristics and microflora of the microbiologically activated carbon employed in the advanced treatment of mixtures of the oil refinery and municipal wastewaters, the organic matter present can be removed to an extent exceeding the adsorption capacity of the adsorbent. 

This section aims to give an overview of adsorption processes of metal ions by activated carbon. Three cases are detailed (1) the adsorption of metal ions onto virgin activated carbon adsorption capacities are given in static and dynamic reactors, and the influence of various operating conditions is shown (2) the adsorption of metal ions onto activated carbon preloaded with organic matter (3) the saturation of activated carbon by organic matter and metal hydroxides after its use in wastewater treatment. The influence of metal hydroxides on activated carbon regeneration is demonstrated. 

Competitive adsorption is important in wastewater treatment because most compounds to be adsorbed exist in solution with other adsorbable compounds. Consequently, a mutual reduction of the adsorptive capacity of each of tlie competing species is usually encountered in these aqueous systems. 

It has been shown that pH exerts a significant effect on oil wastewater treatment by using expanded and hydrophobized (camauba wax) vermicubte [8] pH 9 is the optimum value. Furthermore, it was verified that for standard mineral oh, canola oh, KutweU oh, as well as for refinery effluents, EV exhibits a higher adsorption capacity in comparison with the hydrophobized samples. In this study it was shown that the hydrophobization process does not necessarily enhance oil removal capabifity, but that such phenomena will be influenced by the clay/ hydrophobizant ratio to enhance oil removal by the presence of an hydrophobic compoimd without provoking a decrease of oil removal capabifity by clogging the clay pores. 

Activated carbon (AC) has been most effective adsorbent for the removal of a wide range of contaminants from aqueous or gaseous environment. It is a widely used adsorbent in the treatment of wastewaters due to its exceptionally high surface areas which range from 500 to 1,500 m g, well-developed internal microporosity stmcture [1]. While the effectiveness of ACs to act as adsorbents for a wide range of pollutant materials is well noted and more research on AC modification are presented due to the need to enable ACs to develop affinity for special contaminants removal from wastewater [2], It is, therefore, essential to imderstand the various important factors that influence the adsorption capacity of AC due to their... 

Clays are widely used as adsorbents due to its large surface area. On the other hand, its adsorption capacity for organic molecules, water soluble is very low. This is due to the hydrophilic nature of mineral surfaces. Treatment of clays with orj nic and inorganic reagents increases its adsorption cap>adty. The modified clays can be used as adsorbents in treatment systems of wastewater, thus preventing contamination of groundwater. The... 

Chitosan from different sources was used in the form of beads and flakes and the adsorption capacity for Cu(II) was almost unaffected by the physical form of the polymer while dye adsorption was much higher on beads than on the flakes. Langmuir isotherm was found to fit the adsorption process (Wu et al. 2000). Chitosan and some of its derivates have been used effectively for the adsorption of mercury(II) (Cardenas et al. 2001, Babel and Kumiawan, 2003). Radiation-cross-linked chitosan has been used recently for the treatment of wastewater contaminated with Cr(VI) (Ramnani and Sabhaewal 2006). 

Chitosan/magnetite nano composite beads have the maximum adsorption capacities for Pb(ll), and Ni(ll) at pH 6 under room temperatirre which were as high as 63.33 and 52.55 mg/g respectively. Chitosan magnetite nano composite beads could serve a promising adsorbent not only for Pb(II) and Ni(II) but also for other heavy metal ions in wastewater treatment technology (Hoang finh Tran et al., 2010). 

AN, 0-Carboxy methyl chitosan/cellulose acetate blend nano filtration membrane was prepared in acetone solvent. It had been tested to separate chromium and copper fiom effluent treatment. The highest rejection was observed to be 83.40% and 72.60%, respectively (Alka et al., 2010). A chitosan/cellulose acetate/polyethylene glycol ultra filtration membrane was prepared with DMF as solvent. It was focused to be efficient in removing chromium from artificial and tannery effluent wastewater. The highest rejection rate was responding (Sudha et al., 2008).Cross-linked chitosan/polyvinyl alcohol blend beads were prepared and studied for the adsorption capacity of Cd from wastewater. The maximum adsorption of Cd(II) ions was foimd to be 73.75% at pH 6 (Kumar et al., 2009). 

Adsorption of Cd (II), Cu(II), Ni(II), Pb(II), and Zn(II) from aqueous solution using green coconut shells were investigated by Sousa et al. [69]. Previously, the coconut shells was treated with NaOH 0.1 mol 1" for 3 h and then washed with deionized water, buffer solution (pH 5.0), and dried at 50°C [70]. In the next step the adsorbent submitted alkalized treatment was kept in contact with a single and multi-component solution to removal of Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II) from aqueous solution. Sousa et al. [71] also used sugarcane bagasse for removal of Cu(II), Zn(II), and Ni(II) from wastewater of an electroplating factory. Previously, the material was treated with acid (l.Omol 1 HCl and HNOj solutions) for 24h, washed with deionized water, and dried at room temperature. The adsorbent (20-48 mesh) was then stored in sealed flasks in a vacuum desiccators before use. All the adsorbents showed better adsorption capacity after pretreatments. 

One example (out of many) to illustrate the complexity of adsorption from solution (as compared with gas-phase adsorptions), is the removal of mercury, an unacceptable toxic pollutant in aqueous systems. It is found in wastewaters (before treatment) from such manufacturing industries as chloroalkali, paper and pulp, oil refining, plastic and batteries, and can exist as free metal, as Hg(I) and Hg(II). Mercury adsorption capacity, on AC, increases as the pH of the aqueous systems decreases. Carbons with different activation methods have widely different capacities. Sulfurization of the carbon, loading the carbon with zirconium, as well as the dispersion of FeOOH species over the carbon, enhanced Hg(II) uptake. Mercury vapor can be taken up using AC which have been pre-treated with sulfur, the effect of chemisorbed oxygen being to retard (not prevent) the uptake of mercury, Lopez-Gonzalez et al. (1982). 

Currently, because of the frequency of their occurrence in wastewaters, the adsorption of phenolic compounds on carbons and the influence of surface oxygen complexes on their uptake are the most frequently studied, Radovic et al. (1997). It is well established that an increase in surface acidity of AC, after an oxidation, causes a decrease in phenol adsorption from dilute aqueous solution. For example. Figure 8.8 shows the adsorption isotherms of phenol on oxidized carbons, Mahajan et al. (1980). There was a large decrease in phenol uptake after oxidation, the effect of oxidation not being trivial. This phenol uptake progressively increased as the surface acidity decreased, and the oxidized sample (heat treatment temperature (HTT) 950 °C) had the same adsorption capacity as the original carbon (about 1.5 xmolg" ). 

Crane, R.S., Barton, P., Cartmell, E., Coulon, E, Hillis, P, Judd, S.J., Santos, A., Stephenson, T. Lester, J.N. (2010) Fate and behaviour of copper and zinc in secondary biological wastewater treatment processes. 1. Evaluation of biomass adsorption capacity. Environmental Technology, 31, 705-723. 

Potassium, sodium, calcium and other positively charged ions present in the channel are exchangeable and get replaced by heavy metal ions. Heavy metals present in wastewater (chromium, mercury, lead and cadmium) are effectively adsorbed on zeolites. Clinoptilolite is a widely used zeolite for wastewater treatment due to its higher selectivity and ion exchange capability to remove heavy metal ions including strontium and cesium (Grant et al. 1987). Vaca Mier et al. (2001) studied the selectivity of zeolite for the removal of various heavy metals and observed that zeolites show higher selectivity for lead ions followed by cadmium, copper and cobalt. Table 2.2 (Bailey et al. 1999) shows the some of the reported adsorption capacities of zeolites. 

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