1. A preparation method of a black material for water treatment capable of being regulated and controlled by spectrum is characterized by comprising the following steps:

completely dissolving camphorsulfonic acid in deionized water to obtain a camphorsulfonic acid solution;

dissolving dopamine hydrochloride in deionized water to obtain dopamine hydrochloride solution;

under the condition of stirring, quickly injecting the camphorsulfonic acid solution into the camphorsulfonic acid solution;

stirring, centrifuging and washing with deionized water to obtain the black material for water treatment, which can be regulated and controlled by spectrum.

2. The preparation method of the black material capable of being spectrally modulated for water treatment as claimed in claim 1, characterized in that the method comprises:

under magnetic stirring, completely dissolving 200-400 mg of camphorsulfonic acid in 80mL of deionized water to obtain a camphorsulfonic acid solution;

dissolving 200mg of dopamine hydrochloride in 20mL of deionized water to obtain a dopamine hydrochloride solution;

injecting the dopamine hydrochloride solution into the camphorsulfonic acid solution within 5s under the stirring condition, stirring for 8-16 h, centrifuging, and washing with deionized water for multiple times to obtain the spectrally-controllable black material for water treatment.

3. The method for preparing the black material for water treatment capable of being spectrally modulated according to claim 1, wherein the method comprises the following steps: the particle size of the black material for water treatment which can be regulated and controlled by spectrum is 200 nm-300 nm.

4. A black material capable of being spectrally regulated and controlled for water treatment is characterized in that: prepared by the method of any one of claims 1 to 3.

5. A cellulose film coated with a spectrally-tunable water-treatment black material prepared by the method of any one of claims 1 to 3.

Background

Clean water is a necessity for human survival and social development, but the acquisition channel thereof is insufficient. One effective acquisition channel in recent years is to obtain clean water from seawater and wastewater.

It has now been demonstrated that solar energy can be converted to heat for the evaporation of seawater, producing steam for the desalination of seawater and wastewater. However, in the prior art, the existing seawater desalination material is not salt-resistant and oil-resistant, so that the problems of salt deposition, limited use in polluted sea areas and the like exist.

The rich functional groups of Polydopamine (PDA), such as catechol, amines and imines, not only allow effective removal of organic contaminants, but also impart hydrophilicity to PDA-based materials. In addition, although several PDA-based photothermal materials have been studied to some extent, their light energy collection efficiency in the water and solid states is not high.

The applicant finds in research that the light absorption performance and the photo-thermal behavior of the PDA-based nanomaterial can be further improved by rational structural and functional tailoring. And PDA has demonstrated good light collection and light-to-heat conversion performance, which is also beneficial for solar driven desalination of seawater.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a one-pot method strategy, and polydopamine-set (PDA) Nanoparticles (NPs) with adjustable light absorption characteristics are prepared by direct copolymerization of camphorsulfonic acid and dopamine hydrochloride in an aqueous solution. The polydopamine microstructure provided by the invention is doped with camphorsulfonic acid, so that the energy band gap can be reduced, and the light absorption performance of conventional PDA NPs is improved.

In order to achieve the above technical object, the present invention has the following technical means.

On one hand, the invention provides a preparation method of a black material for water treatment, which can be regulated and controlled by spectrum, in particular,

completely dissolving camphorsulfonic acid in deionized water to obtain a camphorsulfonic acid solution;

dissolving dopamine hydrochloride in deionized water to obtain dopamine hydrochloride solution;

under the condition of stirring, quickly injecting the camphorsulfonic acid solution into the camphorsulfonic acid solution;

stirring, centrifuging and washing with deionized water to obtain PDA with the same size, namely the black material for water treatment which is regulated and controlled by spectrum.

Furthermore, the invention provides a preparation method of the black material for water treatment, which can be regulated and controlled by spectrum, in particular,

under magnetic stirring, completely dissolving 200-400 mg of camphorsulfonic acid in 80mL of deionized water to obtain a camphorsulfonic acid solution;

dissolving 200mg of dopamine hydrochloride in 20mL of deionized water to obtain a dopamine hydrochloride solution;

injecting the dopamine hydrochloride solution into the camphorsulfonic acid solution within 5s under the stirring condition, stirring for 8-16 h, centrifuging and washing with deionized water for three times to obtain PDA with the same size, namely the spectrally-controlled black material for water treatment.

Furthermore, the particle size of the black material for water treatment capable of being spectrally regulated is 200 nm-300 nm.

On the other hand, the invention provides a black material for water treatment, which can be regulated and controlled by a spectrum, and is prepared by the method.

In another aspect, the invention also provides a cellulose membrane coated with the black material for water treatment, which can be spectrally modified.

By adopting the technical scheme, the invention obtains the following technical effects.

The invention provides a simple method for adjusting the absorption spectrum of PDA by one-pot polymerization of dopamine and camphorsulfonic acid.

Compared with the traditional PDA nano-material, NPs have better light absorption capability and full-optical thermal effect, which is reasonably realized by constructing a donor-acceptor structure in a PDA system to reduce energy band gap and increase electron delocalization.

The doping of camphorsulfonic acid does not affect the main structure and photo-thermal mechanism of the polymer, and non-thermal radiation is rarely found in PDA systems.

The invention further coats the doped PDA on the CM film to prepare an evaporation film with good evaporation efficiencyThe evaporation rate of the device can reach 1.53kgm^-2h^-1. Under one sun irradiation, the solar energy conversion efficiency is high (-88.6%).

The invention can provide opportunity for cutting structure and function of PDA-based nano material, and can be used for wide light-catching application.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to specific embodiments. While exemplary embodiments of the invention are shown in the detailed description, it should be understood that the disclosure may be embodied in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

Technical terms in the present invention include: polydopamine (PDA), Nanoparticles (NPs), Cellulose Membranes (CM), Polystyrene (PS), camphorsulfonic acid (CSA).

CSA can be used as an acid catalyst, a chiral auxiliary reagent, and the like, and can also be used in alkyne-imino cyclization reactions promoted by nucleophiles. The invention discloses a one-pot strategy, PDA nano particles with adjustable light absorption characteristics are prepared by direct copolymerization of camphorsulfonic acid and dopamine in aqueous solution, and camphorsulfonic acid is doped in a PDA microstructure, so that an energy band gap can be reduced, the light absorption performance of conventional PDANPs is improved, and the PDA microstructure has good photo-thermal efficiency and can be further applied to generation of interface solar energy steam and seawater desalination.

The basic idea of the present invention is described above, and further explained below by specific examples.

Example 1 preparation of PDA-1.

A black material capable of being regulated and controlled by spectrum for water treatment is prepared by the following steps:

under magnetic stirring for 20min, completely dissolving 200mg of camphorsulfonic acid in 80mL of deionized water to obtain a camphorsulfonic acid solution;

then dissolving 200mg of dopamine hydrochloride in 20mL of deionized water to obtain a dopamine hydrochloride solution;

and then injecting the dopamine hydrochloride solution into the camphorsulfonic acid solution within 5s under the stirring condition, stirring for 8-16 h, centrifuging and washing with deionized water for three times to obtain the spectrally-adjustable black material for water treatment with the same size, which is marked as PDA-1 and has the particle size of 200-300 nm.

Example 2 preparation of PDA-2.

A black material capable of being regulated and controlled by spectrum for water treatment is prepared by the following steps:

under magnetic stirring for 20min, completely dissolving 300mg of camphorsulfonic acid in 80mL of deionized water to obtain a camphorsulfonic acid solution;

then dissolving 200mg of dopamine hydrochloride in 20mL of deionized water to obtain a dopamine hydrochloride solution;

and then injecting the dopamine hydrochloride solution into the camphorsulfonic acid solution within 5s under the stirring condition, stirring for 8-16 h, centrifuging and washing with deionized water to obtain the spectrally-adjustable black material for water treatment with the same size, which is marked as PDA-2 and has the particle size of 200-300 nm.

Example 3 preparation of PDA-3.

A black material capable of being regulated and controlled by spectrum for water treatment is prepared by the following steps:

under magnetic stirring for 20min, completely dissolving 400mg of camphorsulfonic acid in 80mL of deionized water to obtain a camphorsulfonic acid solution;

then dissolving 200mg of dopamine hydrochloride in 20mL of deionized water to obtain a dopamine hydrochloride solution;

and then injecting the dopamine hydrochloride solution into the camphorsulfonic acid solution within 5s under the stirring condition, stirring for 8-16 h, centrifuging and washing with deionized water to obtain the spectrally-adjustable black material for water treatment with the same size, which is marked as PDA-3 and has the particle size of 200-300 nm.

Preparation of comparative example PDA-0

The traditional method for preparing Polydopamine (PDA) comprises the following specific steps,

500mg of dopamine hydrochloride was dissolved in a mixed solution of 90mL of deionized water and 40mL of ethanol, and magnetically stirred at room temperature for 10 min.

2.5mL of an aqueous solution of 28-30% ammonia was injected into the solution, and the color of the solution immediately turned into light brown and gradually turned into black. After stirring and reacting for 16h at room temperature, centrifuging to obtain the traditional polydopamine, which is marked as PDA-0, and washing with deionized water for three times.

Examples of the experiments

See Table 1 for a table of the properties of PDA-0 to PDA-3 of the present invention

TABLE 1 PDA-0 to PDA-3 Performance tables

As can be seen from the table, the camphorsulfonic acid-doped PDA has excellent light absorption and photo-thermal properties, providing a unique opportunity for the generation of water vapor and desalination of seawater.

To further investigate the solar vapor generation performance of PDA-3 coated CM, the present invention measured the water loss during evaporation. Under dark conditions, the evaporation rate of the device was only 0.168kgm^-2h^-1。

In this experiment, the solar conversion efficiency of the PDA coated CM under one sun exposure was 88.6%, much higher than 28.6% of the volume water and 32.3% of pure CM. When the power density of the solar simulator is increased to 4 suns, the PDA-3 coated CM can heat up rapidly and a visible vapor stream can be generated on top of the membrane.

The present invention continues to select PDA-3 with the best photothermal effect as a candidate material for further fabrication of evaporation devices. First, an aqueous solution of PDA-3 (10 mgmL)^-1) 2mL of the solution was deposited on a Cellulose Membrane (CM) to form a bilayer structure membrane as a hydrophilic light absorber. In order to reduce heat loss, the light absorber floats on the water surface, and Polystyrene (PS) foam (with the thickness of 2.24cm) is selected as an insulating layer to prevent the device from directly contacting with the body water. A cotton swab (0.7 cm diameter) was inserted into the center of the styrofoam, water was transported by capillary effect, and then the evaporator apparatus was floated on the water surface. Under the irradiation of sunlight, condensed water is collected from the solar steam to obtain purified water. PDA-3 becomesThe glue is attached to the CM and can be washed by water for a plurality of times without peeling. The light absorption capacity of the PDA-3 coated CM was improved compared to that of the PDA-0 coated CM and the blank CM. The result shows that the absorbance of the PDA-3 coating CM in the ultraviolet (200-400 nm) and visible (400-780 nm) ranges is 94% and 88% respectively. Thus, the PDA-3 based device can absorb most of the solar energy through the main spectrum, and the surface temperature of the PDA-3 coated CM rises rapidly to-37 ℃ within 1min under single day illumination. The core temperature was stabilized at-39.5 ℃. The PS foam insulation has a high solar absorption on the PDA-3 coated CM. The temperature of the PS foam was maintained at approximately room temperature under light, indicating that heat loss from the bulk water by the PS foam was well suppressed.

Solar desalination experiment

In addition, sea water desalting effect is also researched by using sea water and brine in Bohai Bay, and the concentration of metal ions in the sea water is measured by using an inductively coupled plasma spectrometer (ICP-OES). For salt water, after seawater is desalinated, the salinity in the condensation chamber is sharply reduced by at least four orders of magnitude, which is much lower than the salinity level specified by the world health organization and the U.S. environmental protection agency.

Concentration Na of four main ions in Bohai sea water⁺、Mg²⁺、Ca²⁺And K⁺Tests were also performed. The ion concentration after desalination is extremely low, which ensures that the performance of the device is feasible. Note that the salt deposited on the CM surface during evaporation is also easily washed away by the brine. The durability of the PDA-3 coated CM was investigated by 30 cycles (1 hour each) indicating good cycling stability. In addition, the topography and structure of the surface PDA remained unchanged after 30 water evaporations. Notably, the PDA-3 coated CM has a higher evaporation rate under single day light than many established PDA-based evaporators.

PDA-CA was cut into cylindrical shapes with a radius of 2.4cm and a height of 2.2 cm. The PDA-CA was then secured through a hole in an oil resistant rubber plate that tightly covered the top of a 100mL glass beaker. The glass beaker is filled only with seawater or oil-containing seawater. The device was illuminated by a xenon lamp (CEL-PE300L-3A, air quality 1.5 global (AM 1.5G)) as a solar simulator. After switching on the solar simulator, the surface temperature was measured over time by means of a thermal infrared imager (FLIR, T540). The weight loss of water was collected by an electronic balance (OHAUS, CP313) which was used to calculate evaporation rate and efficiency.

TABLE 2 comparison of ion concentrations in seawater and condensed Water vapor

Ion concentration (mg/L)	Na+	Mg2+	Ca2+	K+
					Before desalination	11092	1037	621	311
After desalination	3.67	0.34	0.85	1.64

Oil contamination resistance test

Toluene and soybean oil are selected to simulate the performance of an oil stain detection device (the smaller the COD, the less the organic matter content in the water body)

TABLE 3 results of the oil stain resistance experiment

Adsorption measurement

The absorption measurements were carried out in a temperature-controlled shaker at a stirring speed of 100 rpm. 665nm (MB) and 555nm (Rh B) were selected as dye contaminants to test the light absorption properties of the spectrally tunable water treatment black material of the present invention.

Initially, aqueous solutions containing dye contaminants were prepared at different concentrations. Then, spectrally-tunable water-treatment black material (50mg ± 2mg) was put into 20mL of each solution and shaken in the dark for 24h to reach absorption equilibrium.

The concentrations of MB and Rh B were measured at regular time intervals using an ultraviolet-visible spectrophotometer, which can be calculated by absorbance at 665nm (MB) and 555nm (Rh B).

The absorption capacity of the spectrally-tunable water treatment black material was calculated using the following formula:

wherein c is₀And c_eInitial and equilibrium concentrations of dye contaminants, respectively (mgg)^-1) V is the volume of the aqueous solution and m is the amount (mg) of the spectrally-tunable water treatment black material.

In addition, to study the absorption isotherms, single dye contaminant absorption experiments were performed in aqueous solutions ranging from concentrations of 10mg/L to 100 mg/L. Fitting the obtained absorption isotherm data to the following model

Langmuir model:

wherein c is_e(mgL^-1) Is the equilibrium concentration of dye contaminants, q_e(mgg^-1) Is the amount q of dye pollutants absorbed by a water treatment black material in an equilibrium state and can be regulated by spectrum_m(mgg^-1) Is the maximum absorption capacity, and K_LIs the Langmuir absorption constant.

Friendly type:

wherein c is_e(mgL^-1) Is the equilibrium concentration of dye contaminants, q_e(mgg^-1) Is absorption capacity, K, of black material for water treatment in equilibrium state capable of being regulated and controlled by spectrum_FIs the Freundlich constant and 1/n is the Freundlich coefficient.

The kinetics of the absorption of dye contaminants by spectrally-tunable melanin materials for water treatment were also tested. Initial concentrations of MB and Rh B were both 20mgL^-1. The concentrations of the two dyes were measured at regular time intervals as described above. Absorption capacity (q)_t) The relationship with time (t) is calculated by the following formula:

wherein c is₀And c_tThe dye contaminant concentrations at the initial time and at the given time, respectively, V is the solution volume (mL) and m is the spectrally tunable water treatment black material (mg). For kinetic studies, the data were fitted to the following model. Pseudo first order kinetic equation:

wherein q is_t(mgg^-1) Is the amount of dye contaminant absorbed by the spectrally-tunable water treatment black material at time t (min), q_e(mgg^-1) Is the equilibrium absorption capacity, and k₁(min^-1) Is the rate constant.

Pseudo second order kinetic equation:

wherein q is_t(mgg^-1) Is the amount of dye contaminant absorbed by the spectrally-tunable water treatment black material at time t (min), q_e(mgg^-1) Is the equilibrium absorption capacity, and k₂(gmg^-1min^-1) Is the rate constant.

The test results were as follows:

TABLE 4 thermodynamic parameters for absorption of MB and Rh-B in the dark

TABLE 5 kinetic parameters of MB and Rh-B absorption in the dark

TABLE 6 investigation of the Evaporation Rate of various Water vaporizers under Sun illumination

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In the above examples and experimental examples, dopamine hydrochloride (98%), camphorsulfonic acid (99%), and ammonia water (25-28%) were purchased from Shisheng science and technology Co., Ltd., Beijing, China.

Cellulose membranes were obtained from the fushun civil administration filter paper mill.

All chemicals were used without further purification.

Deionized water was used for all experiments.