Carbon removal from water

The energy requirements for desorbing 1,1-dichloroethane from activated carbon in a stripping—adsorption process for water purification have been calculated at 112 kj/kg (14). Chlorinated hydrocarbons such as 1,1-dichloroethane may easily be removed from water by air or steam stripping. 

Adsorption — An important physico-chemical phenomenon used in treatment of hazardous wastes or in predicting the behavior of hazardous materials in natural systems is adsorption. Adsorption is the concentration or accumulation of substances at a surface or interface between media. Hazardous materials are often removed from water or air by adsorption onto activated carbon. Adsorption of organic hazardous materials onto soils or sediments is an important factor affecting their mobility in the environment. Adsorption may be predicted by use of a number of equations most commonly relating the concentration of a chemical at the surface or interface to the concentration in air or in solution, at equilibrium. These equations may be solved graphically using laboratory data to plot "isotherms." The most common application of adsorption is for the removal of organic compounds from water by activated carbon. 

Organo-modified natural zeolites as new tailored natural materials for removal of cations, anions and even organic pollutants may present fairly large potential for water utility companies. The topic of this study was to examine the oxyanions removal from waters by octadecylammonium-enriched inland clinoptilolite. The 18-carbon chain consisting surfactant attached on the clinoptilolite surface, as to the organic acids of living bodies comparable substances, makes the treatment process economic on scale and cost-effective as well.7... 

IN THE SCIENTIFIC LABORATORY, ALL IMPURITIES [CALCIUM CARBONATE AND SULFATE, AND OTHERS) MUST BE REMOVED FROM WATER TO BE USED AS SOLVENT. THIS IS DONE BY EVAPORATING THE WATER AND CONDENSING THE STEAM. YOU CAN MAKE A DISTILLATION APPARATUS FROM TWO PINT-SIZE CANS. 

Temporary hardness is easily removed from water by boiling. When heated, the calcium hydrogencarbonate decomposes, producing insoluble calcium carbonate. 

As noted above, the water molecule is a polar species, which affects its ability to act as a solvent. Solutes may likewise have polar character. In general, solutes with polar molecules are more soluble in water than nonpolar ones. The polarity of an impurity solute in wastewater is a factor in determining how it may be removed from water. Nonpolar organic solutes are easier to take out of water by an adsorbent species, such as activated carbon, than are more polar solutes. 

The design of the first commercial modules has allowed the commercial application of membrane contactors for some specific operations. This is the case of the Membrana-Charlotte Company (USA) that developed the LiquiCel modules, equipped with polypropylene hollow fibers, for the water deoxygenation for the semiconductor industry. LiquiCel modules have been also applied to the bubble-free carbonation of Pepsi, in the bottling plant of West Virginia [18], and to the concentrations of fruit and vegetable juices in an osmotic distillation pilot plant at Melbourne [19]. Other commercial applications of LiquiCel are the dissolved-gases removal from water, the decarbonation and nitrogenation in breweries, and the ammonia removal from wastewater [20]. 

In the present ocean calcium carbonate formation is dominated by pelagic plants (coccolithophores) and animals (foraminifera, pteropods, and heteropods). Examples are presented in Figure 4.13. Although benthic organisms are important in shoal water sediments, and for dating and geochemical studies in the deep sea sediments, they constitute only a minor portion of the calcium carbonate removed from deep seawater. Shoal water carbonates are discussed in detail in Chapter 5. 

It is interesting to note that the ratio of the relative rate constants for the two solutes, 2,4-D and Silvex, obtained from experiments at low concentration is 2.03 while the ratio of the relative rate constants obtained from experiments at high concentration is 2.11. Thus, it appears that the effect of initial concentration upon the rate at which organic pesticides are removed from water by active carbon is relatively uniform, at least for similar classes of organic pesticides. 

Gadkaree KP, Mach JF, and Stempin J. Ion-removal from water using activated carbon electrodes. US Patent no. 6,214,204. April 2001. 

The steady interest in the effects of the chemistry and physics of the carbon surface on pollutant removal from waters has been ignited by the U.S. Clean Water Act (enacted in 1972, amended as the Water Quality Act in 1987). The most recent interest stems from the Safe Drinking Water Act Amendment of 1996. Activated carbon adsorption has been cited by the U.S. Environmental Protection Agency (www.epa.gov) as one of the best available control technologies. Furthermore, the most recent efforts to understand the adsorption of the same pollutants by soils [7,8] can benefit from comparisons of similarities and differences with respect to the behavior of activated carbons. 

About 50 to 150 g TOC/m (TOC = total organic carbon) of organic carbon are on average removed from water per day. This value is higher, if the water is not break-point chlorinated (see Section 1.1.2.1) or is pretreated with ozone. 

Leenheer and Huffman (1976) have developed a fractionation procedure for aquatic organic solutes called dissolved organic carbon (DOC) fractionation. The procedure for the analytical DOC fractionation is shown in Figure 3. Hydrophobic solutes are first removed from water by adsorption on Am-berlite XAD-8 resin, hydrophilic bases in the effluent are removed by cation-exchange resins, and hydrophilic acids in the effluent are removed by anion-exchange resins. Aquatic humic substances occur primarily in the... 

Chlorides are removed from water with a carbon adsorbent. The carbon particle diameter is 0.2 cm, the viscosity and density of water are 0.8 cP and 1 g/cm, respectively, and the diffusion coefficient of the chlorides in water is 2.37 x 10" cm /s. Calculate the mass transfer coefficient and bed diameter to treat 125,000 cm /s water for superficial velocities of 5, 10, 25, 100, 250 cm/s. Explain the disadvantage of increasing the superficial velocity. 

Since chlorine is removed from water by the carbon, extra care is required from here on to protect against bioburden growth. Carbon beds themselves are good breeding grounds for bacteria. To keep the system in check, a recirculation system as depicted in Fig. 3 is recommended. The constant recirculation avoids water stagnation and reduces viable bioburden growth. 

If the water comes from wells in areas having limestone bedrock, it will contain significant amounts of Ca + and ions (see Chapter 8), which are usually removed during the processing. Calcium can be removed from water by addition of phosphate ions. More commonly, calcium ions are removed by precipitation and filtering of the insoluble salt C COy, the carbonate ions are either added as sodium carbonate, Na2C03, or if sufficient HCO3" naturally present in the water, hydroxide ions can be added in order to convert bicarbonate ions to carbonate (reactions (3) and (4))... 

DOM-water interactions depend on the chemical composition of the DOM mixture. DOM components are classified according to their aqueous solubility fl2]. The humic acid fraction of DOM, which precipitates at pH 2, is more hydrophobic, is more aromatic and has larger molecular weights. In contrast, the fulvic acid fraction of DOM is soluble at all pH values, is more hydrophilic, is less aromatic, and has smaller molecular weights. The low molecular weight and hydrophilic components, and some hydrophilic neutral (e.g., sugars) fractions are the most difficult DOM components to remove from water by both conventional treatment processes and activated carbon adsorption. 

CS-based mixed matrix membranes and nanocomposite membranes are much useful in heavy metal removal. Salehi et al. [82] synthesized amine functionalized multiwalled carbon nanotubes (F-MWCNTs) and utilized to prepare novel CS/polyvinyl alcohol (PVA) thin adsorptive membranes for copper ion removal from water. Copper ion adsorption on the membranes was more favorable at higher CNT contents as well as increased temperatures. The adsorption capacity of the membrane containing 2 wt.% CNTs (20.1 mg/g at 40°C) was almost twice as large as that of the plain membrane (11.1 mg/g). Salehi et al. [83] used PE glycol and amino-modified MWCNTs to modify CS/PVA thin adsorptive membranes for copper ion adsorption. Adsorption capacity of CS/PVA membrane was increased from 11 to 30 mg/g by the addition of 5 wt.% PEG to the blend. Addition of CNTs,... 

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