CN114349379A - Modified coffee grounds, preparation method thereof and pervious concrete using modified coffee grounds - Google Patents

Abstract

The invention discloses modified coffee grounds, a preparation method thereof and pervious concrete using the same. The invention prepares the pervious concrete by adding a mixed aqueous solution of NaOH and cetyl trimethyl ammonium bromide into coffee grounds after alkaline solution pretreatment to neutrality, draining to obtain the modified coffee grounds, and mixing the modified coffee grounds with cement, water, coarse aggregates, fine aggregates, a gelling agent and a water reducing agent. According to the invention, the heavy metal adsorption capacity of the pervious concrete is improved by using the modified coffee grounds, and the risk of heavy metal pollution can be reduced. The method for preparing the pervious concrete by using the modified coffee grounds has the advantages of low cost, easy acquisition, good adsorption performance and small influence on the strength of the pervious concrete. In addition, the invention can efficiently utilize solid wastes, can improve economic benefits and can reduce pollution.

Description

A kind of modified coffee grounds, its preparation method and a kind of pervious concrete using the same

technical field

The invention relates to the field of building materials, in particular to a modified coffee grounds, a preparation method thereof and a permeable concrete using the same.

Background technique

Pervious concrete is a porous lightweight concrete made of coarse aggregate, cement and water. When the permeable concrete floor is used, the surface water can flow into the ground, effectively protect the groundwater, alleviate the urban heat island effect, and promote the circulation of surface water. However, due to the burning of a large amount of automobile fuel, oil leakage, random disposal of electronic waste, and pollution from factories and garbage dumps in the city, when the surface water is discharged into the sewage pipeline network through the ground structure, there are still many heavy metal pollutants enriched, which are harmful to the surrounding areas of the city. The soil causes certain heavy metal pollution, which in turn causes environmental damage such as land degradation and biodiversity reduction. At present, the removal of heavy metal ions by adsorption has the advantages of low cost and wide selection of materials, and has become one of the commonly used methods.

Patent CN110128076A A kind of C20 permeable concrete for high-efficiency air purification and its preparation method By adding an adsorbent composed of nano-titanium dioxide, activated carbon carbon fiber, modified diatomite, moss powder and TPU resin to the permeable concrete, it is mainly used for automobile exhaust. Adsorption and purification, and the cost is high.

Coffee, like tea, is one of the three major beverages in the world. As waste coffee grounds after coffee production, its weight accounts for about 66% of dry coffee beans, that is, 2 tons of coffee grounds are discharged for every 1 ton of instant coffee produced. The current disposal methods for coffee grounds are mainly landfill and incineration. Coffee grounds have a certain pore structure, and the main pore structure is rough micropores, which makes coffee grounds have good adsorption capacity. At the same time, coffee grounds contain more polar functional groups (alcohol, aldehyde, ketone, acid, phenol and ether), which can be used as a polybasic ligand to undergo complex and reaction with metal ions, and can effectively adsorb heavy metal ions.

SUMMARY OF THE INVENTION

In order to solve the heavy metal pollution caused by surface water to the soil around the city, the present invention provides a modified coffee grounds and a permeable concrete material using the same. Coffee grounds can improve the heavy metal adsorption capacity of permeable concrete and reduce the risk of heavy metal pollution.

In order to make up for the above deficiencies, the present invention provides a modified coffee grounds, which is obtained from the coffee grounds after being treated with an alkaline solution to be neutral, reacting with a mixed solution A and then draining; the mixed solution A is NaOH and hexadecane. Aqueous solution mixed with trimethylammonium bromide;

The mass ratio of the coffee grounds and the mixed solution A is 1:10-20, that is, 10-20 g of the mixed solution is required for every 1 g of coffee grounds;

The concentration of NaOH in the mixed solution A is 100g-200g/L, and the concentration of cetyltrimethylammonium bromide is 20-40g/L.

The alkaline solution is selected from any one of KOH and NaOH solutions, and the concentration of the alkaline solution is 0.01-0.05 mol/L.

The specific preparation method of the modified coffee grounds is as follows: the coffee grounds are pretreated with an alkaline solution for 0.5 to 1 hour, and then washed to neutrality to remove the oil in the coffee grounds; then NaOH and cetyltrimethyl are added. The mixed aqueous solution of ammonium bromide was reacted in a magnetic stirrer and then drained to increase the adsorption sites on the surface of the coffee grounds; then the drained solid was washed with deionized water to neutrality, dried, and sieved to a particle size. If the thickness is less than 0.5 mm, the modified coffee grounds according to the present invention are obtained.

The rotating speed of the magnetic stirrer is 200-300rpm, and the reaction time is 1-2h.

The present invention provides a permeable concrete comprising the above-mentioned modified coffee grounds, which is composed of the following raw materials in parts by mass:

The cement is selected from any one of ordinary Portland cement, slag Portland cement and composite Portland cement, preferably codenamed P.O42.5R ordinary Portland cement.

The coarse aggregate is crushed stone, and the fine aggregate is industrial sand.

The particle size ratio of the coarse aggregate is:

The gelling agent is selected from any one of polyvinyl acetate, polyoxyethylene and polyvinylpyrrolidone.

The water-reducing agent is selected from any one of polycarboxylic acid-based water-reducing agents, sulfonic acid-based water-reducing agents, and lignin-based water-reducing agents.

The present invention also provides a method for preparing the permeable concrete, comprising: mixing and stirring the above-mentioned components of cement, water, coarse aggregate, fine aggregate, gelling agent, water reducing agent and modified coffee grounds in proportion, and It is placed in a model and adopts a static pressure forming process, and then steam curing is performed first to improve the strength of the permeable concrete material of the present invention, and finally standard curing is adopted until the age of 28 days.

The specific operation of the above stirring includes: moistening the contact equipment such as the mixer and tools with water, then pouring the cement, gelling agent, water reducing agent and modified coffee grounds into the mixer and stirring evenly, then adding water, and stirring for 3-5 minutes. , and then add the coarse aggregate and fine aggregate into the mixer, and continue to mix until uniform.

The above-mentioned static pressure forming process is as follows: the pre-mixed mixture is placed in the die, the size of the test piece is 100mm × 100mm × 100mm, and it is pressed and formed by a press, and the forming pressure is 3-5 MPa.

The above steam curing is performed for 10 to 15 hours; the standard curing temperature is controlled at (20±3)°C, and the relative humidity is 95%; during curing, the concrete specimens are kept at a distance of 30mm-50mm.

The preparation process of the modified coffee grounds of the invention is simple, and by using the modified coffee grounds, the heavy metal adsorption capacity of the permeable concrete can be improved, and the risk of heavy metal pollution can be reduced. The invention uses the modified coffee grounds to prepare the permeable concrete with low cost, easy acquisition, good adsorption performance, and little influence on the strength of the permeable concrete. In addition, the present invention can efficiently utilize solid waste, which can improve economic benefit and reduce pollution.

Description of drawings

Figure 1 shows the infrared spectra of untreated coffee grounds and modified coffee grounds.

specific embodiment

The technical solutions of the present invention are described in detail below with reference to specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present invention, but the present invention is not limited to the scope of the described embodiments.

(1) Preparation of modified coffee grounds:

50 g of coffee grounds were pretreated with 0.01 mol/L KOH alkaline solution for 60 min, and then washed with deionized water until neutral. Then, it was added to 1L of a mixed solution of 200g/L NaOH and 30g/L cetyltrimethylammonium bromide for reaction, and the reaction was carried out at 250rpm in a magnetic stirrer for 2h to increase the adsorption sites on the surface of coffee grounds. The drained solids were washed with deionized water until neutral, dried and passed through a 40 mesh screen.

The untreated coffee grounds and modified coffee grounds were analyzed by infrared spectroscopy, and the results are shown in Figure 1. Compared with the untreated coffee grounds, the modified coffee grounds have the following groups: -OH (3424.03 cm ^-1 ), carboxyl, ester or aldehyde groups C=O (1773.88 cm ^-1 and 1638.45 cm ^-1 ) , CO of the ester group (1020.69cm-1), CH in the aromatic ring (901.34cm-1, 834.27cm-1 and 783.28cm-1). Obviously, the polar functional groups (ester group, ketone group) of modified coffee grounds increased, and the corresponding adsorption capacity was enhanced.

(2) Preparation of permeable concrete:

Example 1

Using the jarring standard vibrating screen machine developed by the Building Materials Institute of China Academy of Building Research, model: ZBSX 92A, vibration frequency: 221min, swing stroke: 25mm, jarring frequency: 147min, motor power: 0.37Kw. According to the sieve size (mm)>20 (22.2%), 16-20 (28.8%), 10 (40%), <5 (9%) coarse aggregate gradation standard, screen 980g of crushed stone.

Wet the contact equipment such as mixers and tools with water, and then mix the modified coffee grounds (17.5g), ordinary Portland cement (332.5g) with a label of P.O42.5, polyvinyl acetate (52.5g) and polycarboxylate Pour the acid-based superplasticizer (17.5g) into the mixer and stir evenly, then add water (105g), stir for 3-5 minutes, then add crushed stone (980g) and industrial sand (420g) to the mixer, and continue to stir until uniform.

The obtained mixed slurry was poured into a 100mm×100mm×100mm mold, and pressurized by a press to a molding pressure of 3MPa. Steam curing for 10 hours, after sufficient hydration reaction, curing for 28 days at (20±3)°C and relative humidity of 95%, the final product (modified coffee grounds permeable concrete) is obtained after demoulding.

Example 2

Using the jarring standard vibrating screen machine developed by the Building Materials Institute of China Academy of Building Research, model: ZBSX 92A, vibration frequency: 221min, swing stroke: 25mm, jarring frequency: 147min, motor power: 0.37Kw. According to the sieve size (mm)>20 (22.2%), 16-20 (28.8%), 10 (40%), <5 (9%) coarse aggregate gradation standard, screen 980g of crushed stone.

Wet the contact equipment such as mixers and tools with water, and then mix modified coffee grounds (35g), slag Portland cement (315g) with the label P.S 42.5, polyoxyethylene (52.5g) and sulfonic acid-based water reducing agent (17.5g) g) Pour it into the mixer and stir evenly, then add water (105g), stir for 3-5 minutes, then add crushed stone (980g) and industrial sand (420g) into the mixer, and continue to stir until uniform.

The obtained mixed slurry was poured into a 100mm×100mm×100mm mold, and pressurized by a press to a molding pressure of 3MPa. Steam curing for 10 hours, after full hydration reaction, curing for 28 days at (20±3)℃ and 95% relative humidity, the final product (modified coffee grounds permeable concrete) is obtained after demoulding.

Example 3

Using the jarring standard vibrating screen machine developed by the Building Materials Institute of China Academy of Building Research, model: ZBSX 92A, vibration frequency: 221min, swing stroke: 25mm, jarring frequency: 147min, motor power: 0.37Kw. According to the sieve size (mm)>20 (22.2%), 16-20 (28.8%), 10 (40%), <5 (9%) coarse aggregate gradation standard, screen 980g of crushed stone.

Wet contact equipment such as mixers and tools with water, and then mix modified coffee grounds (52.5g), composite Portland cement (297.5g) with the label P.C42.5, polyvinylpyrrolidone (52.5g) and lignin-based Pour the water reducing agent (17.5g) into the mixer and stir well, then add water (105g), stir for 3-5 minutes, then add crushed stone (980g) and industrial sand (420g) into the mixer, and continue to stir until uniform until.

The obtained mixed slurry was poured into a 100mm×100mm×100mm mold, and pressurized by a press to a molding pressure of 3MPa. Steam curing for 10 hours, after sufficient hydration reaction, curing for 28 days at (20±3)°C and relative humidity of 95%, the final product (modified coffee grounds permeable concrete) is obtained after demoulding.

Comparative Example 1

Using the jarring standard vibrating screen machine developed by the Building Materials Institute of China Academy of Building Research, model: ZBSX 92A, vibration frequency: 221min, swing stroke: 25mm, jarring frequency: 147min, motor power: 0.37Kw. According to the sieve size (mm)>20 (22.2%), 16-20 (28.8%), 10 (40%), <5 (9%) coarse aggregate gradation standard, screen 980g of crushed stone.

Moisten the contact equipment such as mixers and tools with water, and then pour the ordinary Portland cement (350g), polyvinyl acetate (52.5g) and polycarboxylate water-reducing agent (17.5g) marked as P.O 42.5 into the mixer Stir well, then add water (105g), stir for 3-5 minutes, then add crushed stone (980g) and industrial sand (420g) into the mixer, and continue to stir until uniform.

The obtained mixed slurry was poured into a 100mm×100mm×100mm mold, and pressurized by a press to a molding pressure of 3MPa. Steam curing for 10 hours, after sufficient hydration reaction, curing for 28 days at (20±3)°C and relative humidity of 95%, the final product (permeable concrete) is obtained after demoulding.

Comparative Example 2

Using the jarring standard vibrating screen machine developed by the Building Materials Institute of China Academy of Building Research, model: ZBSX 92A, vibration frequency: 221min, swing stroke: 25mm, jarring frequency: 147min, motor power: 0.37Kw. According to the sieve size (mm)>20 (22.2%), 16-20 (28.8%), 10 (40%), <5 (9%) coarse aggregate gradation standard, screen 980g of crushed stone.

Wet the contact equipment such as mixers and tools with water, and then mix untreated coffee grounds (17.5g), ordinary Portland cement (332.5g) with a label of P.O42.5, polyvinyl acetate (52.5g) and polycarboxylate Pour the acid-based superplasticizer (17.5g) into the mixer and stir evenly, then add water (105g), stir for 3-5 minutes, then add crushed stone (980g) and industrial sand (420g) to the mixer, and continue to stir until uniform.

The obtained mixed slurry was poured into a 100mm×100mm×100mm mold, and pressurized by a press to a molding pressure of 3MPa. Steam curing for 10 hours, after sufficient hydration reaction, curing for 28 days at (20±3)°C and relative humidity of 95%, the final product (modified coffee grounds permeable concrete) is obtained after demoulding.

Performance Testing

Compressive strength test: The compressive strength of the permeable concrete of Example 1-3 and the control group 1-2 was tested with reference to the standard of T/CSTM 00040-2018 "Test Method for Permeable Concrete", and the results are shown in Table 1. It can be seen from Table 1 that with the increase of the quality of the modified coffee grounds added, the 28-day compressive strength of the prepared permeable concrete decreased slightly. The 28-day compressive strength of the permeable concrete prepared by adding modified coffee grounds was all higher than 20MPa, indicating that the compressive strength of the permeable concrete of the present invention was less affected after adding modified coffee grounds. The results obtained in the tests of Example 1 and Comparative Example 2 show that the incorporation of untreated coffee grounds significantly reduces the strength of pervious concrete.

Table 1 Compressive strength of permeable concrete with different coffee grounds content

Adsorption performance test: Cu ²⁺ heavy metal ion solution was prepared with analytical purity of copper nitrate. The initial concentration of the heavy metal ion solution was 1000 mg/L, the pH value of the solution was 7, and the temperature was constant at 25°C. The modified coffee grounds permeable concrete cube test block was placed in a beaker containing 1L of heavy metal ion solution and covered with a plastic film, the adsorption duration was 24h, and the concentration of copper ions in the solution was measured by ultraviolet spectrophotometer at each adsorption time. The adsorption capacity q _t of modified coffee grounds permeable concrete to heavy metal ions is calculated as follows.

In the formula, C ₀ and C ₁ are the initial concentration of the heavy metal ion solution and the concentration after adsorption for 24 hours, mg/L; V is the volume of the heavy metal ion solution, and the volume used in the present invention is 1 L; w is the quality of the modified coffee grounds, g. The results are shown in Table 2. It can be seen from Table 2 that the permeable concrete without modified coffee grounds can absorb a small amount of copper ions due to its porosity. 8 times, and with the increase in the mass fraction of modified coffee grounds incorporated, the amount of copper ion adsorption continued to increase. In addition, the adsorption capacity of pervious concrete incorporating untreated coffee grounds is much lower than that of permeable concrete incorporating modified coffee grounds. The above results show that the permeable concrete prepared from modified coffee grounds has better adsorption performance.

Table 2 Adsorption capacity of permeable concrete with different coffee grounds content

Claims (10)

1. A modified coffee grounds, characterized in that: the modified coffee grounds are obtained by treating coffee grounds to be neutral through an alkaline solution, reacting with the mixed solution A and draining; the mixed solution A is a mixed aqueous solution of NaOH and hexadecyl trimethyl ammonium bromide;

the mass ratio of the coffee grounds to the mixed solution A is 1: 10-20 parts of;

the concentration of NaOH in the mixed solution A is 100 g/L-200 g/L, and the concentration of cetyl trimethyl ammonium bromide is 20 g/L-40 g/L.

2. The modified coffee grounds according to claim 1, wherein the alkaline solution is selected from any one of KOH and NaOH solutions, and the concentration of the alkaline solution is 0.01-0.05 mol/L.

3. A method for preparing modified coffee grounds according to claim 1 or 2, which comprises the following steps: pretreating coffee grounds for 0.5-1 h by using an alkaline solution, and then cleaning the coffee grounds to be neutral; and then adding a mixed aqueous solution of NaOH and hexadecyl trimethyl ammonium bromide, reacting in a magnetic stirrer, draining, cleaning the drained solid with deionized water to be neutral, drying, and sieving until the particle size is less than 0.5mm to obtain the modified coffee grounds.

4. The method as claimed in claim 3, wherein the rotation speed of the magnetic stirrer is 200-300rpm, and the reaction time is 1-2 h.

5. The pervious concrete containing the modified coffee grounds of claim 1 or 2, which is characterized by comprising the following raw materials in parts by mass:

20-30 parts by mass of cement,

5-15 parts by mass of water,

50-60 parts by mass of coarse aggregate,

15-25 parts by mass of a fine aggregate,

2-3 parts by mass of a gelling agent,

1-2 parts by mass of a water reducing agent,

1-3 parts of modified coffee grounds.

6. The pervious concrete according to claim 5, wherein the cement is selected from any one of ordinary portland cement, slag portland cement and composite portland cement;

the coarse aggregate adopts broken stones, and the fine aggregate adopts industrial sand;

the coarse aggregate has the following grain size ratio:

the gelling agent is selected from any one of polyvinyl acetate, polyoxyethylene and polyvinylpyrrolidone;

the water reducing agent is selected from any one of a polycarboxylic acid water reducing agent, a sulfonic acid water reducing agent and a lignin water reducing agent.

7. The pervious concrete of claim 6, characterized in that said cement is p.o42.5r ordinary portland cement.

8. The method for preparing a pervious concrete according to any one of claims 5 to 7, comprising: mixing and stirring the cement, the water, the coarse aggregate, the fine aggregate, the gelling agent, the water reducing agent and the modified coffee grounds according to a proportion, placing the mixture in a model, adopting a static pressure forming process, then carrying out steam curing firstly to improve the strength of the pervious concrete material, and finally adopting standard curing until the age reaches 28 days;

the static pressure forming process comprises the following steps: and (3) putting the pre-mixed mixture into a pressing die, wherein the test piece size is 100mm multiplied by l00mm multiplied by l00mm, and pressing and molding the mixture by a press machine to form the mixture under the pressure of 3-5 MPa.

9. The method for preparing pervious concrete according to claim 8, wherein the concrete operation of stirring comprises: wetting contact equipment such as a stirrer, tools and the like with water, then pouring cement, a gelling agent, a water reducing agent and modified coffee grounds into the stirrer to be uniformly stirred, adding water into the stirrer to be stirred for 3-5 minutes, then adding coarse aggregates and fine aggregates into the stirrer, and continuously stirring the mixture until the mixture is uniform.

10. The method for preparing pervious concrete according to claim 8, wherein the steam curing is carried out for 10-15 hours; the standard curing temperature is controlled to be (20 +/-3) DEG C, and the relative humidity is 95 percent; and during maintenance, the concrete test pieces keep the distance of 30-50 mm.

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