阅读说明：本技术 一种基于初级自由基计算紫外高级氧化工艺氧化剂最佳投加浓度的方法 (Method for calculating optimal adding concentration of oxidant in ultraviolet advanced oxidation process based on primary free radicals ) 是由 孙佩哲 孟坛 陈曦 于 2021-09-07 设计创作，主要内容包括：本发明属于环境工程水处理领域,具体涉及一种基于初级自由基计算紫外高级氧化工艺氧化剂最佳投加浓度的方法。主要包括：一个用于计算紫外高级氧化工艺氧化剂最佳投加浓度的简单公式。本发明推导得到的简单公式可以为水处理中基于紫外的高级氧化工艺氧化剂投加浓度的优化提供一种简单的计算方法,为工程应用中紫外高级氧化工艺的优化和挑选提供理论参考。(The invention belongs to the field of water treatment in environmental engineering, and particularly relates to a method for calculating the optimal adding concentration of an oxidant in an ultraviolet advanced oxidation process based on primary free radicals. The method mainly comprises the following steps: a simple formula for calculating the optimal adding concentration of the oxidant in the ultraviolet advanced oxidation process. The simple formula obtained by derivation can provide a simple calculation method for optimizing the adding concentration of the ultraviolet-based advanced oxidation process oxidant in water treatment, and provides theoretical reference for optimization and selection of the ultraviolet advanced oxidation process in engineering application.)

1. A method for calculating the optimal adding concentration of an oxidant in an ultraviolet advanced oxidation process based on primary free radicals mainly comprises the following steps: a simple formula for calculating the optimal adding concentration of the oxidant in the ultraviolet advanced oxidation process is as follows:

1) first, UV/H with only OH as a single PRS₂O₂For example, a calculated UV/H is derived based on the primary free radical₂O₂Simple formula of theoretical optimum oxidant addition concentration:

2) will be based on [. OH]_ssThe derived simple formula is popularized and applied to other UV-based AOPs for generating various PRSs, including UV/FAC, UV/PDS and UV/NH₂Cl and UV/PAA.

2. The simple formula for calculating the optimal adding concentration of the oxidant in the ultraviolet advanced oxidation process according to claim 1 is characterized in that:

1) the formula deduced by the invention can quickly and accurately measure the optimal adding concentration of the theoretical oxidant of the ultraviolet advanced oxidation process, and provides theoretical guidance for the application of the ultraviolet advanced oxidation in the aspect of water treatment;

2) the simple formula for calculating the optimal adding concentration of the theoretical oxidant, which is obtained by derivation in the invention, can be popularized and applied to other newly proposed ultraviolet-based advanced oxidation processes (such as UV/peroxyformic acid and UV/NO)₂ ^-UV/PMS, etc.) provides a simple evaluation method for the energy consumption of the engineering;

3) the invention deduces a simple formula for calculating the optimal adding concentration of the theoretical oxidant, and provides a simple method for the comparison of the ultraviolet-based advanced oxidation process.

Technical Field

The invention belongs to the field of water treatment in environmental engineering, and particularly relates to a method for calculating the optimal adding concentration of an oxidant in an ultraviolet advanced oxidation process based on primary free radicals.

Background

Ultraviolet-based advanced oxidation processes (UV-based aops) have received much attention because they can effectively remove organic contaminants from water. UV-based AOPs typically use chemical oxidizing agents, such as hydrogen peroxide (H)₂O₂) Free chlorine (FAC), Peroxodisulfate (PDS), monochloramine (NH)₂Cl), peracetic acid (PAA), etc., which, in combination with ultraviolet irradiation, generate highly active radicals that can effectively reduce pollutants in water. The optimization of energy consumption is based on ultravioletIs an important subject in the field of water treatment.

The removal effect of UV-based AOPs on pollutants in water is determined by the steady-state concentration of Primary Reactive Species (PRS) in the system ([ PRS)]_ss) The steady-state concentration of the free radicals in the system is determined by the generation rate of the free radicals and the consumption rate of the free radicals, the generation rate of the free radicals can be increased by increasing the concentration of the oxidizing agent, but the oxidizing agent can react with the free radicals to further consume the generated free radicals, so the steady-state concentration of the free radicals in the system generally rises firstly and then falls with the increase of the concentration of the oxidizing agent. For a particular UV-based AOP, the highest PRS is produced]_ssThe concentration of the oxidant is the optimal oxidant adding concentration (C) of the process_{opt-theoretical}). However, due to the lack of theoretical research on process optimization, particularly on oxidant addition concentration optimization, the engineering application of UV-based AOPs is generally optimized one by one according to the requirements of water plants, which limits the large-scale popularization and application of the UV-based AOPs in engineering.

In summary, a simple and efficient method for optimizing the adding concentration of the oxidant in the ultraviolet advanced oxidation process is needed.

Disclosure of Invention

The invention aims to provide a method for calculating the theoretical optimal adding concentration of an ultraviolet advanced oxidation process oxidant based on primary free radicals, a simple formula is obtained by deduction, a simple calculation method is provided for optimizing the adding concentration of the ultraviolet-based advanced oxidation process oxidant in water treatment, and theoretical reference is provided for optimizing and selecting the ultraviolet advanced oxidation process in engineering application

The first technical scheme provided by the invention for solving the technical problems in the prior art is as follows: the method for calculating the theoretical optimal adding concentration of the ultraviolet advanced oxidation process oxidant based on the primary free radical comprises the following steps:

1) first, UV/H with only OH as a single PRS₂O₂For example, a calculated UV/H is derived based on the primary free radical₂O₂Simple formula of theoretical optimum oxidant addition concentration:

UV/H₂O₂the removal effect on the pollutants in water is determined by the steady-state concentration of OH in the system ([. OH)]_ss) And in the system [. OH ]]_ssThe Generation Rate (g.r.) and the consumption Rate (s.e.) of the radicals are determined together:

ultraviolet photolysis of H₂O₂OH (exemplified by a 254nm wavelength) can be generated, and g.r. can be expressed as:

wherein, I₀(Einstein·L^-1·s^-1) Represents the light intensity at 254nm, phi (mol. Einstein)^-1) Represents H₂O₂Quantum yield at 254nm, A_b(cm^-1) Represents the absorption of water at 254nm,. epsilon. (M)^-1·cm^-1) Represents H₂O₂L (cm) represents the effective optical path of the reactor.

In engineering applications, the uv reactor is generally designed to be a cylinder with a high reflective surface to ensure that as much light as possible is absorbed by the reaction system, and since light is continuously reflected, the optical path of the uv reactor is generally considered to be large enough, so equation 2 can be simplified as:

in the ultraviolet advanced oxidation water treatment process, the consumption of free radicals is mainly caused by the consumption capacity of water quality to the free radicals (S)_c，s^-1) And the consumption of free radicals by the oxidizing agent itself. Thus UV/H in engineering applications₂O₂In the system [. OH [. ]]_ssCan be expressed as:

wherein k (M)^-1-s^-1) Represents OH and H₂O₂Second order rate constant of reaction, C (M)^-1) And) represents the oxidant concentration. For a particular treatment target water sample, [. OH ]]_ssIs about H₂O₂Function of concentration, [. OH]_ssWith H₂O₂The increase in concentration increases and then decreases. Produce the highest [. OH [. ] OH]_ssH of (A) to (B)₂O₂The concentration of (C) is the optimal oxidant addition concentration of the target water sample_{opt-theoretical}). Therefore, equation 4 is derived:

setting the value of the derivative formula to zero, C can be obtained_{opt-theoretical}Expression (c):

in the formula 6, A_bε and k can be determined by simple measurement or reference in the literature, so we can determine S for water quality_cUV/H can be obtained₂O₂The optimal adding concentration of the theoretical oxidant for treating a certain water sample.

2) Is popularized to other advanced oxidation processes based on ultraviolet

UV/H₂O₂Only OH is produced as its unique PRS. For UV/PAA,. OH is the main PRS produced by it, and is therefore based on [. OH [. OH]_ssThe simple formula derived is applicable to UV/PAA. For UV/FAC, UV/PDS, UV/NH₂Cl, the PRS produced in addition to OH includes Cl or SO₄ ^-. OH in the system comprises two parts (TGR)_·OH): (1) OH and (2). Cl or SO produced by direct photolysis of an oxidant₄ ^-The resulting OH was converted. The research finds that the Cl or the SO₄ ^-The rate of generation (dGR)_·ClOr dGR_·SO4-) With the Total OH Generation Rate (TGR)_·OH) Proportional ratio, i.e. TGR_·OH/dGR_·ClOr TGR_·OH/dGR_·SO4-The ratio α is constant (fig. 1). Thus, changes in the concentration of OH can be used in place of changes in the concentration of PRS, based on [. OH]_ssThe derived simple formula can be popularized and applied to other UV-based AOPs generating various PRSs.

Has the advantages that:

the invention has the beneficial effects that:

1) the invention provides a method for calculating the theoretical optimal adding concentration of an ultraviolet advanced oxidation process based on primary free radicals, and the theoretical optimal adding concentration of an oxidant in the ultraviolet advanced oxidation process can be quickly and accurately measured by using a formula deduced by the method, so that theoretical guidance is provided for the application of ultraviolet advanced oxidation in the aspect of water treatment.

2) The simple formula for calculating the optimal adding concentration of the theoretical oxidant, which is obtained by derivation, can be popularized and applied to other newly proposed ultraviolet-based advanced oxidation processes (such as UV/peroxyformic acid and UV/NO)₂ ^-UV/PMS, etc.) provides a simple method for assessing the energy consumption of the engineering plant.

3) The invention deduces a simple formula for calculating the optimal adding concentration of the theoretical oxidant, and provides a simple method for the comparison of the ultraviolet-based advanced oxidation process.

Drawings

FIG. 1 is TGR_·OH/dGR_·ClOr TGR_·OH/dGR_·SO4-A ratio alpha variation graph;

FIG. 2 is a comparison of optimal oxidant addition concentrations of different water qualities in different ultraviolet advanced oxidation systems.

Detailed Description

The invention is further illustrated by the following specific examples and the accompanying drawings. The examples are intended to better enable those skilled in the art to better understand the present invention and are not intended to limit the present invention in any way.

Example 1

In this embodiment, water samples from different sources, including 1 sample each of lake water/river water, secondary effluent of sewage treatment plant, and tap water, are selected, and the theoretical optimal addition concentration of the oxidant in different ultraviolet advanced oxidation processes is determined by a formula, which specifically comprises the following steps:

1) 1 sample of each of lake water/river water, secondary effluent of a sewage treatment plant and tap water is filtered through a 0.45-micron water system filter membrane for standby application (the first of various water samples in figure 2).

2) Firstly, measuring A of lake water/river water, secondary effluent of sewage treatment plant and tap water sample by using ultraviolet spectrophotometer_b(cm^-1) 0.43, 0.17 and 0.04 respectively; the pH values of lake water/river water, secondary effluent water of a sewage treatment plant and tap water samples are respectively 7.50, 7.77 and 8.14 by using a pH meter

3) The S of lake water/river water, secondary effluent of sewage treatment plants and tap water samples is measured through experiments_c(s^-1) Are respectively 4.96 multiplied by 10⁵、 2.10×10⁵、2.21×10⁵。

4) Obtaining H by consulting a reference₂O₂、FAC、NH₂Cl, PDS and PAA/PAA^-Molar absorptivity of epsilon (M)^-1·cm^-1) 18.6, 62, 382, 22 and 10/59, respectively.

5) Obtaining H by consulting a reference₂O₂、FAC、NH₂Cl, PDS and PAA/PAA^-Second order reaction rate constant k (M) with OH^-1·s^-1) Respectively as follows: 2.70X 10⁷、2.00×10⁹、5.10×10⁸、1.40×10⁷And 9.97X 10⁹/9.33×10⁸。

6) The above values are substituted into the formula 6, so that the optimal adding concentration of the oxidant of different water samples in different ultraviolet advanced oxidation processes (the first water sample in fig. 2) can be obtained. Of note are PAA and PAA^-(pKa ═ 8.2) andthe k of OH is very different and its presence ratio in different water samples is taken into account.

The results of this embodiment are as follows:

the optimal adding concentrations of the oxidants of different water samples in different ultraviolet advanced oxidation processes are respectively calculated according to a formula and are shown in figure 2: the optimal adding concentration of the oxidant in different ultraviolet advanced oxidation processes for the same water sample generally follows the following rule: PDS > H₂O₂＞NH₂Cl≈PAA＞FAC。

It should be understood that the embodiments and examples discussed herein are illustrative only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.