Powder activated carbon adsorption reuse problem solution

Activated carbon is a widely used adsorbent in the field of water treatment. It contains a large number of micropores and has a large specific surface area. For some difficult substances in sewage, such as surfactants, phenols, pesticides, fuels, biodegradable organic matter and heavy metals. Ions and the like have high processing efficiency.

The strong adsorption performance of activated carbon is related to its large specific surface area. During the activation of carbon particles, the voids formed between the crystal lattices form pores of various shapes and sizes, and the area of ​​the pore walls is the total surface area of ​​the activated carbon, and the adsorption mainly occurs on the surfaces of the pores. Activated carbon can enhance its surface activity during the activation process. Therefore, activated carbon can not only remove non-polar substances in water, but also adsorb polar solute, even some traces of metal ions and their compounds.

Activated carbon adsorption is a deep treatment technology for wastewater with broad application prospects. It has the advantages of wide adaptability, good treatment effect, recyclable useful materials, reusable adsorbent, etc. It can be widely used in the deep treatment of water. However, this process has higher requirements for influent pretreatment, higher operating costs, large system, and troublesome operation.

1. Principle of activated carbon adsorption

Activated carbon is an adsorbent made of carbon-containing materials as a raw material and carbonized and activated at a high temperature. Activated carbon products are produced by using coal, nut shells, wood chips, etc. as raw materials, forming, crushing, carbonizing and activating. Since the volatile organic compounds are removed during the manufacturing process, many pores of different shapes and sizes are formed inside, so the activated carbon is rich in pores (0.6~0.9cm3/g), and the specific surface area is as high as 700~1000m2/g, which is the adsorption capacity of activated carbon. The main reason for strong and large adsorption capacity. The adsorption characteristics of activated carbon are not only affected by the pore structure, but also by the chemical properties of the activated carbon surface. Activated carbon is a non-polar adsorbent that adsorbs non-polar, weakly polar organic materials in water.

The adsorption form of activated carbon is divided into physical adsorption and chemical adsorption. Physical adsorption is related to van der Waals forces by molecular force adsorption. Physical adsorption is reversible, low selectivity, multi-layer adsorption, and easy to desorb. The combination of chemisorption and valence bond is an exothermic process. Chemisorption is selective and only works for one or a few specific substances. Chemical adsorption is irreversible, relatively stable, and difficult to desorb. After the adsorption is saturated, the activated carbon can be reused after regeneration. The purpose of the regeneration is to remove the adsorbate from the pores of the adsorbent by some method in order to prevent the structure of the adsorbent from occurring or rarely change. reuse.

Activated carbon is generally classified into two types: Granular activated carbon (GAC) and powdered activated carbon (PAC). Powdered carbon has strong adsorption capacity and is easy to manufacture, but regeneration is difficult. Granular activated carbon is expensive but renewable and recyclable.

2. Application of powder activated carbon in MBFB

In the MBFB reaction system, powdered activated carbon (PAC) is a bioactive carbon (BAC) due to the adsorption of a large number of microorganisms, so that PAC not only has the adsorption and enrichment of small organic pollutants, but also the presence of PAC on microorganisms. Adsorption and protection, adsorption of dissolved oxygen by PAC, decomposition of small molecules by microorganisms under local high contaminant concentration and high dissolved oxygen, and bioregeneration of PAC. PAC, microorganisms, dissolved oxygen, pollutants and other elements under the action of high-intensity fluidization, mixing, mass transfer and shear, achieve efficient decomposition of micro-polluted small molecular organic matter.

1) PAC adsorption and enrichment of small molecular organic matter PAC can enrich pollutants to form local high concentration zones, which is beneficial to microbial growth and decomposition of micro-polluted small molecules organic matter;

2) adsorption and protection of microorganisms by PAC;

3) PAC adsorption to dissolved oxygen, as the diameter of activated carbon particles becomes smaller, the specific surface area increases, and the adsorption of dissolved oxygen by PAC becomes stronger and stronger;

4) Decomposition of small molecules by microbes, MBFB process adsorption and enrichment of microorganisms, pollutants and dissolved oxygen by PAC; through the protection of microorganisms by PAC, microbes can effectively use trace organic pollutants as the basis The substance, dissolved oxygen as an electron acceptor, decomposes organic matter in the micro-polluted water body, and realizes deep purification of water quality;

5) Bioregeneration of PAC, the biofilm on the surface of activated carbon has oxidative decomposition effect on the adsorbed organic matter, and can restore the adsorption capacity of activated carbon by biodegradation to realize the biological regeneration of PAC. In the MBFB system, high-intensity three-phase mass transfer, mixing, The turbulent flow, shearing and friction between the activated carbon particles cause the aging biofilm on the surface of the activated carbon to continuously fall off, so that MBFB maintains efficient adsorption and biodegradation functions.

3, MBFB core equipment - super flux inorganic ceramic membrane

The inorganic ceramic membrane system developed by Seattle Environmental Technology Co., Ltd. is based on the research of ordinary ceramic membranes. Through high-tech transformation, it reduces membrane fouling, greatly increases membrane flux, and effectively overcomes the application of inorganic ceramic membranes in water treatment. The biggest obstacle (expensive price, small membrane flux), effectively separate the powder activated carbon, the process is simple, and it is possible to apply the inorganic ceramic membrane to water treatment.

4. Main technical parameters of inorganic ceramic membrane:

Film thickness: 50-60 μm, membrane pore size 0.01-0.5 μm;

Porosity rate: 44-46%;

Filtration pressure: 1.0 Mpa, recoil pressure: 0.4 Mpa or less;

Membrane material: double film, outer film TiO2; inner film Al2O3-ZrO2 composite film.