Activated Carbon Adsorption

{"news_id":8356,"is_preview":0,"news_info":{"id":8356,"company_id":176,"user_id":411,"author":"","website_id":781,"pub_date":"2023-11-17 10:30:54","urla":"adsorption","description":"Activated carbon is a hydrophobic adsorbent used in various \u2026","image_url":"https:\/\/oss.matchpages.cn\/matchpages\/common\/2023\/1016\/2756\/652ce28f1e617\/Activated-Carbon-Adsorption.webp","image_alt":"Activated Carbon Adsorption","title":"Adsorption","content":"<h1><strong><span style=\"color: #169179; font-size: 18pt;\">Activated Carbon Adsorption<\/span><\/strong><\/h1>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Adsorption is a phenomenon that when the fluid is in contact with the porous medium, a certain component or multiple components in the fluid will accumulate on the surface of the medium. It is also that the surface of a substance (mainly solid substance) adsorbs molecules or ions in the surrounding liquid, gas.<\/span><\/p>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">It can be divided into physical adsorption and chemical adsorption.<\/span><\/p>\n<ul style=\"line-height: 1.75;\">\n<li><span style=\"text-decoration: underline;\"><span style=\"color: #000000; text-decoration: underline;\">Physical adsorption: the adsorption between the adsorbent and the adsorbate through intermolecular forces.<\/span><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><span style=\"color: #000000; text-decoration: underline;\">Chemical adsorption: the chemical interaction between the adsorbent and the adsorbate is caused by the chemical bond force.<\/span><\/span><\/li>\n<\/ul>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Commonly used adsorbents in wastewater treatment are&nbsp;<span style=\"text-decoration: underline; color: #169179;\"><strong><a style=\"color: #169179; text-decoration: underline;\" href=\"activated-carbon\" target=\"_blank\" rel=\"noopener\" data-page_id=\"19575\" data-page_name=\"Activated Carbon\uff5cACC\" data-page_type=\"menuPage\">activated carbon<\/a><\/strong><\/span>, sulfonated coal, active enzyme, zeolite, activated clay, diatomaceous earth, coke, wood charcoal, sawdust, etc.<\/span><\/p>\n<h2 style=\"line-height: 1.75;\"><strong><span id=\"The-properties-of-activated-carbon\" style=\"color: #169179; font-size: 14pt;\">The properties of activated carbon<\/span><\/strong><\/h2>\n<h3 style=\"line-height: 1.75;\"><strong><span id=\"Manufacture-of-activated-carbon\" style=\"color: #000000; font-size: 12pt;\">Manufacture of activated carbon<\/span><\/strong><\/h3>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Activated carbon is a hydrophobic adsorbent made from carbon-based materials (such as wood and coal) after high-temperature carbonization and activation. Carbonization is the pyrolysis of raw materials into carbon residue to produce polycyclic aromatic substances similar to graphite. Activation is to turn the pyrolyzed carbon residue into a porous structure.<\/span><\/p>\n<h3 style=\"line-height: 1.75;\"><strong><span id=\"The-pore-structure-and-distribution-of-activated-carbon\" style=\"color: #000000; font-size: 12pt;\">The pore structure and distribution of activated carbon<\/span><\/strong><\/h3>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Activated carbon consists of fine pores. According to the diameter of the pores, it can be divided into<span style=\"text-decoration: underline;\"> micropores ( &lt; 2nm), mesopores (2-50 nm), macropores (&gt;50 nm).<\/span><\/span><\/p>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Specific surface area: the total surface area per unit of mass of adsorbent. The specific surface area of commonly-used activated carbon is 500-1700m<sup>2<\/sup>\/g, of which 95% are micropores.<\/span><\/p>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">It is the micropores that make the activated carbon have the adsorption function, and the function of the macropores is to introduce the solution into the adsorption function zone of the micropores.<\/span><\/p>\n<h3 style=\"line-height: 1.75;\"><strong><span id=\"Chemical-properties\" style=\"color: #000000; font-size: 12pt;\">Chemical properties<\/span><\/strong><\/h3>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Activated carbon is composed of flat graphite-type microcrystals. The carbon atoms at the edge of the microcrystals, due to the unsaturation of covalent bonds, are easy to combine with other elements such as oxygen and hydrogen to form various oxygen-containing functional groups, which make the activated carbon have some activity. The ones that have been confirmed include hydroxy groups (-OH), carboxyl groups (-COOH).<\/span><\/p>\n<h2 style=\"line-height: 1.75;\"><strong><span id=\"Adsorption\" style=\"color: #169179; font-size: 14pt;\">Adsorption<\/span><\/strong><\/h2>\n<h3 style=\"line-height: 1.75;\"><strong><span id=\"Equilibrium-concentration\" style=\"color: #000000; font-size: 12pt;\">Equilibrium concentration<\/span><\/strong><\/h3>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">When the adsorption rate and the desorption rate are equal, that is, when the adsorbed quantity per unit time is equal to the desorbed quantity, the concentration of the adsorbate in the solution and that of the adsorbent surface will not change and reach equilibrium. At this time, the concentration of the adsorbate in the solution becomes the equilibrium concentration.<\/span><\/p>\n<h3 style=\"line-height: 1.75;\"><strong><span id=\"Adsorption-isotherm\" style=\"color: #000000; font-size: 12pt;\">Adsorption isotherm<\/span><\/strong><\/h3>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Under certain temperature conditions, the amount of adsorption increases with the increase of the equilibrium concentration of adsorbate. The curve in which the adsorption amount changes with the equilibrium concentration is called the adsorption isotherm. Due to the complexity of the liquid phase, there is no unified adsorption theory, so the gas phase adsorption isotherm is used.<\/span><\/p>\n<p class=\"font-weight-bold\" style=\"line-height: 1.75;\"><em><span style=\"color: #000000;\">Adsorption models<\/span><\/em><\/p>\n<ul style=\"line-height: 1.75;\">\n<li><span style=\"text-decoration: underline;\"><span style=\"color: #000000; text-decoration: underline;\">Type I adsorption isotherm: Langmuir equation, Freundlich equation;<\/span><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><span style=\"color: #000000; text-decoration: underline;\">Type II adsorption isotherm: Brunauer&ndash;Emmett&ndash;Teller (BET) theory.<\/span><\/span><\/li>\n<\/ul>\n<h3 style=\"line-height: 1.75;\"><strong><span id=\"Adsorption-rate\" style=\"color: #000000; font-size: 12pt;\">Adsorption rate<\/span><\/strong><\/h3>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Adsorption rate is the amount of material adsorbed by a unit weight of adsorbent in a unit time. The adsorption process can be divided into three stages: the membrane diffusion stage, the internal diffusion stage, and the adsorption reaction stage. Because the adsorption reaction stage is very fast, the adsorption rate is mainly controlled by the first two stages.<\/span><\/p>\n<p class=\"font-weight-bold\" style=\"line-height: 1.75;\"><em><span style=\"color: #000000;\">Influencing factors<\/span><\/em><\/p>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">(1) The property of the adsorbent: the larger the specific surface area of the adsorbent, the stronger the adsorption capacity.<\/span><\/p>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">(2) The properties of adsorbate<\/span><\/p>\n<ul style=\"line-height: 1.75;\">\n<li><span style=\"color: #000000;\">Solubility: The lower the solubility, the easier it is to be adsorbed.<\/span><\/li>\n<li><span style=\"color: #000000;\">Surface free energy: The more the surface free energy decreases, the easier it is to be adsorbed.<\/span><\/li>\n<li><span style=\"color: #000000;\">Polarity.<\/span><\/li>\n<li><span style=\"color: #000000;\">The size and degree of unsaturation of adsorbed molecules.<\/span><\/li>\n<li><span style=\"color: #000000;\">Concentration of adsorbate.<\/span><\/li>\n<\/ul>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">(3) pH value of wastewater: Activated carbon generally has a higher adsorption rate in acidic solutions than in alkaline solutions. In addition, pH has an effect on the existence and solubility of the adsorbate, thereby affecting the adsorption effect.<\/span><\/p>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">(4) Coexisting substances<\/span><\/p>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">(5) Temperature: The adsorption process is an exothermic process, the amount of adsorption decreases when the temperature rises, and vice versa. The temperature has a greater impact on the gas phase, less on the liquid phase.<\/span><\/p>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">(6) Contact time: It should be ensured that the adsorbate and the adsorbent have a certain contact time to make the adsorption close to equilibrium.<\/span><\/p>\n<h3 style=\"line-height: 1.75;\"><em><strong><span id=\"Adsorption-operation\" style=\"color: #000000; font-size: 12pt;\">Adsorption operation<\/span><\/strong><\/em><\/h3>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Static: Under the condition that the wastewater does not flow, the adsorption operation is carried out.<\/span><\/p>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Dynamic: The adsorption operation under the condition of flowing wastewater.<\/span><\/p>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Dynamic equipment commonly used in wastewater treatment includes fixed bed, moving bed and fluidized bed.<\/span><\/p>\n<p class=\"font-weight-bold\" style=\"line-height: 1.75;\"><em><strong><span style=\"color: #000000;\">Fixed bed<\/span><\/strong><\/em><\/p>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">When the wastewater continuously passes through the adsorption equipment filled with adsorbent, the adsorbate in the wastewater is adsorbed by the adsorbent. If the amount of adsorbent is sufficient, the concentration of adsorbate in the wastewater flowing from the adsorption equipment can be reduced to zero. <\/span><\/p>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">After the adsorbent has been used for a period of time, the concentration of adsorbate in the effluent gradually increases. When it reaches a certain value, the water should be stopped and the adsorbent should be regenerated. The adsorption and&nbsp;<span style=\"text-decoration: underline;\"><strong><span style=\"color: #169179;\"><a style=\"color: #169179; text-decoration: underline;\" href=\"renewable-raw-material-activated-carbon\" target=\"\" rel=\"noopener\" data-page_id=\"19556\" data-page_name=\"Renewable Raw Material Activated Carbon\uff5cACC\" data-page_type=\"menuPage\">regeneration<\/a><\/span><\/strong><\/span>&nbsp;can be performed alternately in the same equipment, or the saturated adsorbent can be discharged and sent to the regeneration equipment.<\/span><\/p>\n<p class=\"font-weight-bold\" style=\"line-height: 1.75;\"><em><strong><span style=\"color: #000000;\">Moving bed<\/span><\/strong><\/em><\/p>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">The raw water flows from the bottom of the adsorption tower into countercurrent contact with the adsorbent, the treated water flows out from the top of the tower, the regenerated adsorbent is added from the top of the tower, and the adsorbent close to adsorption saturation is intermittently removed from the bottom of the tower.<\/span><\/p>\n<h2 style=\"line-height: 1.75;\"><strong><span id=\"Activated-carbon-adsorption-used-in-wastewater-treatment\" style=\"color: #169179; font-size: 14pt;\">Activated carbon adsorption used in wastewater treatment<\/span><\/strong><\/h2>\n<h3 style=\"line-height: 1.75;\"><strong><span id=\"The-adsorption-of-organic-matter-by-activated-carbon\" style=\"color: #000000; font-size: 12pt;\">The adsorption of organic matter by activated carbon<\/span><\/strong><\/h3>\n<p style=\"line-height: 1.75;\"><span style=\"color: #000000;\">The active adsorption method is mostly used to remove small amounts of organic matter in a dissolved state that cannot be removed by biological, physical, or chemical methods. However, some organic matter is easy to adsorb, and some organic matter is difficult to adsorb. Whether the activated carbon adsorption method can be used should be determined by adsorption test.<\/span><\/p>\n<h3 style=\"line-height: 1.75;\"><strong><span id=\"Factors-that-influence-activated-carbon-adsorption\" style=\"color: #000000; font-size: 12pt;\">Factors that influence activated carbon adsorption<\/span><\/strong><\/h3>\n<ul>\n<li style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Molecular structure &mdash; Aromatic compounds are easier to adsorb than general aliphatics.<\/span><\/li>\n<li style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Interfacial tension &mdash; The more the liquid interfacial tension is reduced, the easier it is to be adsorbed.<\/span><\/li>\n<li style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Solubility &mdash; Activated carbon is a hydrophobic substance, so the stronger the hydrophobicity of the adsorbed substance, the easier it is to be adsorbed.<\/span><\/li>\n<li style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Ionicity and polarity &ndash; Some of the organic acids and amines are weakly acidic or weakly alkaline after being dissolved in water. This kind of organic matter has a larger adsorption capacity when it is in a non-dissociated molecular state than when it is ionized.<\/span><\/li>\n<li style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Molecular weight &mdash; the larger the molecular weight, the stronger the adsorption.<\/span><\/li>\n<li style=\"line-height: 1.75;\"><span style=\"color: #000000;\">pH &mdash; Reducing the pH value of the wastewater to 2-3, and then performing adsorption, usually can increase the removal rate of organic matter, because the proportion of organic acids in the wastewater to form ions is small, so the adsorption capacity is large.<\/span><\/li>\n<li style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Concentration &mdash; Generally, as the concentration of organic matter increases, the amount of adsorption increases exponentially.<\/span><\/li>\n<li style=\"line-height: 1.75;\"><span style=\"color: #000000;\">Coexisting substances &mdash; some metal ions such as mercury, chromic acid, iron, etc. will undergo redox reactions on the surface of activated carbon, and the products will precipitate in the particles and hinder adsorption.<\/span><\/li>\n<\/ul>","discuss":0,"seo_title":"Activated Carbon Adsorption | ACC","seo_keyword":"activated carbon,Activated Carbon Adsorption,activated carbon filter,granular activated carbon","seo_describe":"Activated carbon is a hydrophobic adsorbent used in various liquid and gas phase applications. What are the factors that influence activated carbon adsorption?","track_code":"","viewer":"","source_copy_id":0,"sort":78,"status":0,"data_time":"2023-11-17 10:30:54","create_time":"2023-11-17 10:30:08","update_time":"2025-04-02 09:56:43","type_items":[{"id":2083,"website_id":781,"name":"Activated Carbon","urla":""}],"tag_items":[]}}

<h1><strong><span style="color: #169179; font-size: 18pt;">Activated Carbon Adsorption</span></strong></h1>
<p style="line-height: 1.75;"><span style="color: #000000;">Adsorption is a phenomenon that when the fluid is in contact with the porous medium, a certain component or multiple components in the fluid will accumulate on the surface of the medium. It is also that the surface of a substance (mainly solid substance) adsorbs molecules or ions in the surrounding liquid, gas.</span></p>
<p style="line-height: 1.75;"><span style="color: #000000;">It can be divided into physical adsorption and chemical adsorption.</span></p>
<ul style="line-height: 1.75;">
<li><span style="text-decoration: underline;"><span style="color: #000000; text-decoration: underline;">Physical adsorption: the adsorption between the adsorbent and the adsorbate through intermolecular forces.</span></span></li>
<li><span style="text-decoration: underline;"><span style="color: #000000; text-decoration: underline;">Chemical adsorption: the chemical interaction between the adsorbent and the adsorbate is caused by the chemical bond force.</span></span></li>
</ul>
<p style="line-height: 1.75;"><span style="color: #000000;">Commonly used adsorbents in wastewater treatment are <span style="text-decoration: underline; color: #169179;"><strong><a style="color: #169179; text-decoration: underline;" href="activated-carbon" target="_blank" rel="noopener" data-page_id="19575" data-page_name="Activated Carbon｜ACC" data-page_type="menuPage">activated carbon</a></strong></span>, sulfonated coal, active enzyme, zeolite, activated clay, diatomaceous earth, coke, wood charcoal, sawdust, etc.</span></p>
<h2 style="line-height: 1.75;"><strong><span id="The-properties-of-activated-carbon" style="color: #169179; font-size: 14pt;">The properties of activated carbon</span></strong></h2>
<h3 style="line-height: 1.75;"><strong><span id="Manufacture-of-activated-carbon" style="color: #000000; font-size: 12pt;">Manufacture of activated carbon</span></strong></h3>
<p style="line-height: 1.75;"><span style="color: #000000;">Activated carbon is a hydrophobic adsorbent made from carbon-based materials (such as wood and coal) after high-temperature carbonization and activation. Carbonization is the pyrolysis of raw materials into carbon residue to produce polycyclic aromatic substances similar to graphite. Activation is to turn the pyrolyzed carbon residue into a porous structure.</span></p>
<h3 style="line-height: 1.75;"><strong><span id="The-pore-structure-and-distribution-of-activated-carbon" style="color: #000000; font-size: 12pt;">The pore structure and distribution of activated carbon</span></strong></h3>
<p style="line-height: 1.75;"><span style="color: #000000;">Activated carbon consists of fine pores. According to the diameter of the pores, it can be divided into<span style="text-decoration: underline;"> micropores ( < 2nm), mesopores (2-50 nm), macropores (>50 nm).</span></span></p>
<p style="line-height: 1.75;"><span style="color: #000000;">Specific surface area: the total surface area per unit of mass of adsorbent. The specific surface area of commonly-used activated carbon is 500-1700m<sup>2</sup>/g, of which 95% are micropores.</span></p>
<p style="line-height: 1.75;"><span style="color: #000000;">It is the micropores that make the activated carbon have the adsorption function, and the function of the macropores is to introduce the solution into the adsorption function zone of the micropores.</span></p>
<h3 style="line-height: 1.75;"><strong><span id="Chemical-properties" style="color: #000000; font-size: 12pt;">Chemical properties</span></strong></h3>
<p style="line-height: 1.75;"><span style="color: #000000;">Activated carbon is composed of flat graphite-type microcrystals. The carbon atoms at the edge of the microcrystals, due to the unsaturation of covalent bonds, are easy to combine with other elements such as oxygen and hydrogen to form various oxygen-containing functional groups, which make the activated carbon have some activity. The ones that have been confirmed include hydroxy groups (-OH), carboxyl groups (-COOH).</span></p>
<h2 style="line-height: 1.75;"><strong><span id="Adsorption" style="color: #169179; font-size: 14pt;">Adsorption</span></strong></h2>
<h3 style="line-height: 1.75;"><strong><span id="Equilibrium-concentration" style="color: #000000; font-size: 12pt;">Equilibrium concentration</span></strong></h3>
<p style="line-height: 1.75;"><span style="color: #000000;">When the adsorption rate and the desorption rate are equal, that is, when the adsorbed quantity per unit time is equal to the desorbed quantity, the concentration of the adsorbate in the solution and that of the adsorbent surface will not change and reach equilibrium. At this time, the concentration of the adsorbate in the solution becomes the equilibrium concentration.</span></p>
<h3 style="line-height: 1.75;"><strong><span id="Adsorption-isotherm" style="color: #000000; font-size: 12pt;">Adsorption isotherm</span></strong></h3>
<p style="line-height: 1.75;"><span style="color: #000000;">Under certain temperature conditions, the amount of adsorption increases with the increase of the equilibrium concentration of adsorbate. The curve in which the adsorption amount changes with the equilibrium concentration is called the adsorption isotherm. Due to the complexity of the liquid phase, there is no unified adsorption theory, so the gas phase adsorption isotherm is used.</span></p>
<p class="font-weight-bold" style="line-height: 1.75;"><em><span style="color: #000000;">Adsorption models</span></em></p>
<ul style="line-height: 1.75;">
<li><span style="text-decoration: underline;"><span style="color: #000000; text-decoration: underline;">Type I adsorption isotherm: Langmuir equation, Freundlich equation;</span></span></li>
<li><span style="text-decoration: underline;"><span style="color: #000000; text-decoration: underline;">Type II adsorption isotherm: Brunauer–Emmett–Teller (BET) theory.</span></span></li>
</ul>
<h3 style="line-height: 1.75;"><strong><span id="Adsorption-rate" style="color: #000000; font-size: 12pt;">Adsorption rate</span></strong></h3>
<p style="line-height: 1.75;"><span style="color: #000000;">Adsorption rate is the amount of material adsorbed by a unit weight of adsorbent in a unit time. The adsorption process can be divided into three stages: the membrane diffusion stage, the internal diffusion stage, and the adsorption reaction stage. Because the adsorption reaction stage is very fast, the adsorption rate is mainly controlled by the first two stages.</span></p>
<p class="font-weight-bold" style="line-height: 1.75;"><em><span style="color: #000000;">Influencing factors</span></em></p>
<p style="line-height: 1.75;"><span style="color: #000000;">(1) The property of the adsorbent: the larger the specific surface area of the adsorbent, the stronger the adsorption capacity.</span></p>
<p style="line-height: 1.75;"><span style="color: #000000;">(2) The properties of adsorbate</span></p>
<ul style="line-height: 1.75;">
<li><span style="color: #000000;">Solubility: The lower the solubility, the easier it is to be adsorbed.</span></li>
<li><span style="color: #000000;">Surface free energy: The more the surface free energy decreases, the easier it is to be adsorbed.</span></li>
<li><span style="color: #000000;">Polarity.</span></li>
<li><span style="color: #000000;">The size and degree of unsaturation of adsorbed molecules.</span></li>
<li><span style="color: #000000;">Concentration of adsorbate.</span></li>
</ul>
<p style="line-height: 1.75;"><span style="color: #000000;">(3) pH value of wastewater: Activated carbon generally has a higher adsorption rate in acidic solutions than in alkaline solutions. In addition, pH has an effect on the existence and solubility of the adsorbate, thereby affecting the adsorption effect.</span></p>
<p style="line-height: 1.75;"><span style="color: #000000;">(4) Coexisting substances</span></p>
<p style="line-height: 1.75;"><span style="color: #000000;">(5) Temperature: The adsorption process is an exothermic process, the amount of adsorption decreases when the temperature rises, and vice versa. The temperature has a greater impact on the gas phase, less on the liquid phase.</span></p>
<p style="line-height: 1.75;"><span style="color: #000000;">(6) Contact time: It should be ensured that the adsorbate and the adsorbent have a certain contact time to make the adsorption close to equilibrium.</span></p>
<h3 style="line-height: 1.75;"><em><strong><span id="Adsorption-operation" style="color: #000000; font-size: 12pt;">Adsorption operation</span></strong></em></h3>
<p style="line-height: 1.75;"><span style="color: #000000;">Static: Under the condition that the wastewater does not flow, the adsorption operation is carried out.</span></p>
<p style="line-height: 1.75;"><span style="color: #000000;">Dynamic: The adsorption operation under the condition of flowing wastewater.</span></p>
<p style="line-height: 1.75;"><span style="color: #000000;">Dynamic equipment commonly used in wastewater treatment includes fixed bed, moving bed and fluidized bed.</span></p>
<p class="font-weight-bold" style="line-height: 1.75;"><em><strong><span style="color: #000000;">Fixed bed</span></strong></em></p>
<p style="line-height: 1.75;"><span style="color: #000000;">When the wastewater continuously passes through the adsorption equipment filled with adsorbent, the adsorbate in the wastewater is adsorbed by the adsorbent. If the amount of adsorbent is sufficient, the concentration of adsorbate in the wastewater flowing from the adsorption equipment can be reduced to zero. </span></p>
<p style="line-height: 1.75;"><span style="color: #000000;">After the adsorbent has been used for a period of time, the concentration of adsorbate in the effluent gradually increases. When it reaches a certain value, the water should be stopped and the adsorbent should be regenerated. The adsorption and <span style="text-decoration: underline;"><strong><span style="color: #169179;"><a style="color: #169179; text-decoration: underline;" href="renewable-raw-material-activated-carbon" target="" rel="noopener" data-page_id="19556" data-page_name="Renewable Raw Material Activated Carbon｜ACC" data-page_type="menuPage">regeneration</a></span></strong></span> can be performed alternately in the same equipment, or the saturated adsorbent can be discharged and sent to the regeneration equipment.</span></p>
<p class="font-weight-bold" style="line-height: 1.75;"><em><strong><span style="color: #000000;">Moving bed</span></strong></em></p>
<p style="line-height: 1.75;"><span style="color: #000000;">The raw water flows from the bottom of the adsorption tower into countercurrent contact with the adsorbent, the treated water flows out from the top of the tower, the regenerated adsorbent is added from the top of the tower, and the adsorbent close to adsorption saturation is intermittently removed from the bottom of the tower.</span></p>
<h2 style="line-height: 1.75;"><strong><span id="Activated-carbon-adsorption-used-in-wastewater-treatment" style="color: #169179; font-size: 14pt;">Activated carbon adsorption used in wastewater treatment</span></strong></h2>
<h3 style="line-height: 1.75;"><strong><span id="The-adsorption-of-organic-matter-by-activated-carbon" style="color: #000000; font-size: 12pt;">The adsorption of organic matter by activated carbon</span></strong></h3>
<p style="line-height: 1.75;"><span style="color: #000000;">The active adsorption method is mostly used to remove small amounts of organic matter in a dissolved state that cannot be removed by biological, physical, or chemical methods. However, some organic matter is easy to adsorb, and some organic matter is difficult to adsorb. Whether the activated carbon adsorption method can be used should be determined by adsorption test.</span></p>
<h3 style="line-height: 1.75;"><strong><span id="Factors-that-influence-activated-carbon-adsorption" style="color: #000000; font-size: 12pt;">Factors that influence activated carbon adsorption</span></strong></h3>
<ul>
<li style="line-height: 1.75;"><span style="color: #000000;">Molecular structure — Aromatic compounds are easier to adsorb than general aliphatics.</span></li>
<li style="line-height: 1.75;"><span style="color: #000000;">Interfacial tension — The more the liquid interfacial tension is reduced, the easier it is to be adsorbed.</span></li>
<li style="line-height: 1.75;"><span style="color: #000000;">Solubility — Activated carbon is a hydrophobic substance, so the stronger the hydrophobicity of the adsorbed substance, the easier it is to be adsorbed.</span></li>
<li style="line-height: 1.75;"><span style="color: #000000;">Ionicity and polarity – Some of the organic acids and amines are weakly acidic or weakly alkaline after being dissolved in water. This kind of organic matter has a larger adsorption capacity when it is in a non-dissociated molecular state than when it is ionized.</span></li>
<li style="line-height: 1.75;"><span style="color: #000000;">Molecular weight — the larger the molecular weight, the stronger the adsorption.</span></li>
<li style="line-height: 1.75;"><span style="color: #000000;">pH — Reducing the pH value of the wastewater to 2-3, and then performing adsorption, usually can increase the removal rate of organic matter, because the proportion of organic acids in the wastewater to form ions is small, so the adsorption capacity is large.</span></li>
<li style="line-height: 1.75;"><span style="color: #000000;">Concentration — Generally, as the concentration of organic matter increases, the amount of adsorption increases exponentially.</span></li>
<li style="line-height: 1.75;"><span style="color: #000000;">Coexisting substances — some metal ions such as mercury, chromic acid, iron, etc. will undergo redox reactions on the surface of activated carbon, and the products will precipitate in the particles and hinder adsorption.</span></li>
</ul>