Gong Wenqi, Han Pei, Wang Hukun, Liu Yanju, Rao Boqiong
(School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, Hubei 430070)
Abstract: Rectorite-water quenching was studied Process conditions for the preparation of slag and rectorite-fly ash particle adsorption materials, regeneration methods and conditions for removing heavy metals from copper smelting industrial wastewater. The test results show that: the ratio of rectorite to water quenching slag is 1:1, and 10% additive (IS) and 50% water are added. When the roasting temperature is 400°C, the granular adsorption material not only has good adsorption effect , and the loss rate is low. Without adjusting the pH value of copper smelting industrial wastewater, the amount of particle adsorption material is 0.05g/cm3, the reaction time is 40 min, and the adsorption temperature is 25°C (normal temperature), the removal of Cu2+, Pb2+, Zn2+, Cd2+, and Ni2+ The rates are 98.2%, 96.3%, 78.6%, 86.2%, and 64.2% respectively. The ratio of rectorite to fly ash is 1:1, and 15% additive (IS) and 50% water are added. When the roasting temperature is 500°C, the granular adsorption material not only has a good adsorption effect, but also has a good dissipation rate. lower. Without adjusting the pH value of copper smelting industrial wastewater, the amount of particle adsorption material is 0.07g/cm3, the reaction time is 60 min, and the adsorption temperature is 25°C (normal temperature), the removal of Cu2+, Pb2+, Zn2+, Cd2+, and Ni2+ The rates are 98.9%, 97.5%, 96.7%, 90.2%, and 79.1% respectively. The treated water meets the first-level standard of the National Comprehensive Wastewater Discharge Standard (GB8978-1996). The regeneration effect of saturated particle adsorbent materials with 1 mol/L sodium chloride solution is good. This particulate adsorbent material has the advantages of easy separation, reusability, good treatment effect, and broad application prospects [1~11].
Keywords rectorite; water quenching slag; fly ash; granular adsorbent material; regeneration; copper smelting industrial wastewater
About the first author: Gong Wenqi (1948—), male , Han nationality, native of Wuhan City, Hubei Province, professor, doctoral supervisor, majoring in mineral processing. Tel: 027-62574946, E-mail: gongwenqi@yahoo.com.cn.
Rectorite is a regular interlayer clay mineral composed of dioctahedral mica and dioctahedral montmorillonite at a ratio of 1:1. It has a unique structure, strong adsorption and cation exchange properties [1 ,2]. Scholars at home and abroad have studied the use of rectorite and its modified products to treat wastewater [3~5], and have made gratifying progress. However, researchers have found that the main problems with these powdery adsorbent materials when treating wastewater are: the adsorbent materials have fine particle sizes and are easily dispersed and pulverized when exposed to water, making subsequent solid-liquid separation very difficult and easy to form new industrial sludge. This kind of industrial sludge is more harmful to the environment due to secondary pollution due to the enrichment of adsorbed substances; the adsorbent materials cannot be reused, the adsorbed substances cannot be recycled, and the treatment cost is greatly increased [6]. In order to solve these problems, this article discusses the process conditions and regeneration methods for the preparation of rectorite-water quenching slag and rectorite-fly ash particle adsorption materials and their application in the treatment of copper smelting industrial wastewater. The removal of heavy metal ions such as Cu2+, Pb2+, Zn2+, Cd2+, Ni2+ provides a low-cost adsorption material with good removal effect.
1. Test part
(1) Test materials
The rectorite used in the test is produced in Zhongxiang, Hubei and provided by Hubei celebrity Rectorite Technology Company. Its chemical composition is: SiO243.82%, Al2O334.25%, Fe2O31.59%, CaO 3.76%, K2O 0.93%, Na2O 1.54%, MgO 0.36%, TiO22.97%; its mineral composition is: Rectorite 85 %; illite 10%; kaolinite 5%.
The blast furnace water quenching slag used in the test was obtained from the ironmaking plant of Wuhan Iron and Steel Group Corporation. Its chemical composition is: SiO232.98%, Al2O316.67%, Fe2O30.70%, CaO 35.99%, K2O 0.44%, MgO 8.52%, TiO21.43%. X-ray diffraction phase analysis shows that it is an amorphous phase.
The fly ash used in the test is dry discharge fly ash from Hubei Huadian Group Huangshi Power Generation Co., Ltd. Its chemical composition is: SiO254.72%, Al2O328.65%, Fe2O34.14%, CaO 3.39%, K2O 1.68%, MgO 0.78%, TiO21.22%. Its mineral composition is: quartz 15%, mullite 15%, amorphous phase 70%.
The copper smelting industrial wastewater used in the test was taken from the actual wastewater from the copper smelting plant of Daye Nonferrous Metals Company, Huangshi City, Hubei Province. The water quality analysis results are: Cu2+2.62 mg/dm3, Pb2+0.63 mg/dm3, Zn2+3.92 mg/dm3, Cd2+0.58 mg/dm3, Ni2+1.48 mg/dm3, pH 6.5.
(2) Test instruments
D/MAX-RB X-ray diffractometer, ST-2000 specific surface area and pore size measuring instrument, XTLZ multi-purpose vacuum filter, F97-series closed assay Sample preparation crusher, XSB-70 B type ф200 standard sieve vibrating machine, 20~400 mesh standard inspection sieve, PHS-3C acidity meter, SKFO-01 electric drying oven, SX2-4-13 muffle furnace, THZ-82 Constant temperature water bath oscillator, AB204-N electronic balance, JY38plus plasma single-channel scanning direct reading spectrometer (ICP-AES).
(3) Test method
1. Sample preparation
Rectorite samples were purified by repeated dispersion-sedimentation method, and the water quenched residue and powder were The coal ash samples were used directly. The samples were dried and crushed and then sieved to less than 240 mesh for later use.
2. Preparation of rectorite-water quenching slag and rectorite-fly ash particle adsorption materials
Place the prepared water quenching slag or fly ash with rectorite Stone, plus additives (industrial starch, IS for short) and water, mix evenly according to a certain proportion, age for 24 hours, and make particles with a particle size of 1 to 3 mm, then send them to a muffle furnace for roasting for 2 hours, and then naturally cool to room temperature. That is the required particle adsorption material.
3. Treatment of copper smelting industrial wastewater
Add 100 mL of copper smelting industrial wastewater into a 250 mL Erlenmeyer flask, add a certain amount of granular adsorption material, and place it in a constant temperature water bath for oscillation After reacting for a certain period of time in the reactor (oscillation frequency 110 r/min), centrifuge, take out the supernatant, measure the concentration of heavy metal ions and calculate the adsorption removal rate η (%): η = (Co-Ce)/Co×100 %, where Co and Ce are the concentrations of heavy metal ions in the solution before and after adsorption (mg/dm3) respectively.
4. Determination of the loss rate of granular adsorbent materials
Accurately weigh a certain amount of granular adsorbent (recorded as G1) and place it in a 250 mL Erlenmeyer flask with a stopper. Add 100 mL of deionized water, oscillate in a constant temperature water bath oscillator with an oscillation frequency of 110 r/min for a certain time under certain temperature conditions, use deionized water to wash away the powder produced by the crushing of the granular adsorbent material, and then put the wet The granular adsorbent material is placed in an oven at 103 to 105°C and baked to constant weight, and then weighed after cooling to room temperature (recorded as G2). The calculation formula for the loss rate P (%) is [7]:
P=(G1-G2)/G1×100%
II. Test results and discussion
In order to simplify the treatment process and reduce the treatment cost, this test was conducted on copper smelting industrial wastewater. It was conducted under natural pH (i.e. without pH adjustment) conditions, and the influence of the process conditions for the preparation of granular adsorbent materials, wastewater treatment process conditions, and recycling methods of granular adsorbent materials on the removal rate of heavy metal elements in wastewater was examined.
(1) Influence of process conditions for the preparation of granular adsorbent materials
1. Influence of roasting temperature
Based on the test results, the removal rate of Cu and the particles were comprehensively considered For the loss rate of adsorbent materials, it is determined that the roasting temperatures of rectorite-water quenching slag and rectorite-fly ash particle adsorbent materials are 400°C and 500°C respectively. At this time, the removal rate of Cu is higher and the loss of particulate adsorbent materials is rate is lower.
2. Effect of the mixing ratio of rectorite and water quenching slag or fly ash
The effect of the mixing ratio of rectorite and water quenching slag or fly ash on the removal rate of Cu in wastewater It can be seen from the influence test results that when the rectorite content increases from 10% to 20%, the Cu removal rate increases. Later, as the rectorite content increases, the Cu removal rate shows a downward trend, and the loss rate increases with the increase of rectorite content. There has been a downward trend with increasing rectorite content. When the rectorite content is greater than 50%, the loss rate is close to 0. From the perspective of effective utilization of water quenching slag and fly ash, the rectorite content is determined to be 50%, that is, the ratio of water quenching slag or fly ash to rectorite is 1:1, and the removal rate of Cu is high and The loss rate is very low.
3. Effect of additive proportion
Test results of the effect of additive proportion on the removal of Cu from wastewater by rectorite-water quenching slag or rectorite-fly ash particle adsorption materials It can be seen that when the additive content of these two particle adsorption materials is 10% and 15% respectively, the removal rate of Cu is very high, but the loss rate is very low. From the perspective of removal effect and cost, it is determined that these two particles The additive contents in the adsorbent materials were 10% and 15% respectively.
(2) The effect of granular adsorption materials on removing heavy metal elements from copper smelting industrial wastewater
According to the preparation conditions determined by the above experiments: the ratio of rectorite to water quenching slag is 1: 1. Add another 10% additive and 50% water, and the roasting temperature is 400°C; the ratio of rectorite to fly ash is 1:1, add another 15% additive and 50% water, and the roasting temperature is 500°C. ℃; respectively made into granular adsorption materials to conduct conditional tests on the removal of heavy metal elements from copper smelting industrial wastewater.
1. The influence of reaction time
Under the conditions of normal temperature (25℃) and the dosage of particle adsorption material is 0.03g/cm3, the reaction time has an important effect on the removal of heavy metals from copper smelting industrial wastewater. The test results of the influence of elements show that as the reaction time prolongs, the removal rate of heavy metal elements gradually increases. After 40 minutes, the rectorite-water quenching slag particle adsorption material is used, or the rectorite-fly ash particle adsorption material is used. After 60 minutes of material removal, the removal rate tends to be balanced. Therefore, the reaction times using these two particulate adsorbent materials were determined to be 40 min and 60 min respectively.
2. Influence of adsorption temperature
When the dosage of granular adsorbent is 0.03g/cm3, the reaction time of rectorite-water quenching slag particle adsorption material is 40 min, and the reaction time of rectorite-water quenching slag particle adsorption material is 40 min. - Under the condition that the reaction time of the fly ash particle adsorption material is 60 minutes, the effect of adsorption temperature on the removal of heavy metal elements from copper smelting industrial wastewater was tested. The results show that at 25°C, both particle adsorbents have the highest removal rates of heavy metal elements. Therefore, the adsorption temperature was determined to be 25°C.
3. Influence of the dosage of granular adsorbent materials
At normal temperature (25°C), the reaction time of rectorite-water quenching slag and rectorite-fly ash particle adsorbent materials Under the conditions of 40 min and 60 min respectively, the effect of the dosage of these two granular adsorbents on the removal of heavy metal elements from copper smelting industrial wastewater was tested. The results showed that as the dosage of adsorbent increased, the removal rate of heavy metal elements gradually increased. When the amount of rectorite-water quenching slag particle adsorbent is greater than 0.03g/cm3 and the amount of rectorite-fly ash particle adsorbent is greater than 0.05g/cm3, the heavy metal element removal rate increases slowly. Therefore, from a cost perspective, the dosage of these two granular adsorbents was determined to be 0.03g/cm3 and 0.05g/cm3 respectively.
(3) Orthogonal test results
The above discussed the effects of each single factor (time, temperature, dosage) conditions on rectorite-water quenching slag or rectorite-pulverized coal Effect of ash particle adsorption materials on the removal of heavy metal elements from copper smelting industrial wastewater. In order to explore the optimal removal effect of heavy metal elements in wastewater by particle adsorption materials under the interaction of various single factors, an orthogonal experiment with three factors and two levels was conducted. The results are shown in Tables 1 and 2.
Table 1 Orthogonal test results of copper smelter wastewater treated with rectorite-water quenching slag
Table 2 Orthogonal test results of copper smelter wastewater treated with rectorite-fly ash
After analyzing the orthogonal test results, the following conclusions can be drawn:
1) The use of rectorite-water quenching slag particle adsorption materials to treat copper smelting wastewater can be achieved under natural pH conditions When the reaction temperature is 25°C (i.e. normal temperature), the reaction time is 40 minutes, and the amount of particle adsorption material is 0.05g/cm3, the removal rates of Cu2+, Pb2+, Zn2+, Cd2+, and Ni2+ in wastewater are 98.2% and 98.2%, respectively. 96.3%, 78.6%, 86.2%, 64.2%. The residual concentrations of Cu2+, Pb2+, Zn2+, Cd2+, and Ni2+ in the treated wastewater were all lower than the first-level standard of the National Comprehensive Wastewater Discharge Standard (GB8978-1996).
2) The use of rectorite-fly ash particle adsorption materials to treat copper smelting wastewater can be carried out under natural pH conditions. The reaction temperature is 25°C (i.e. normal temperature), the reaction time is 60 minutes, and the particle adsorption When the material dosage is 0.07g/cm3, the removal rates of Cu2+, Pb2+, Zn2+, Cd2+, and Ni2+ in wastewater are 98.9%, 97.5%, 96.7%, 90.2%, and 79.1% respectively. Cu2+, Pb2+, and Zn2+ in wastewater after treatment The residual concentrations of , Cd2+ and Ni2+ are all lower than the first-level standard of the National Comprehensive Wastewater Discharge Standard (GB8978-1996).
3) Rectorite-water quenching slag and rectorite-fly ash particle adsorption materials have strong adsorption activity for heavy metal elements in copper smelting industrial wastewater, which is mainly due to water quenching Both slag and fly ash are porous materials with high activity [8-12]. Rectorite is a regular interlayer clay mineral composed of dioctahedral mica and dioctahedral montmorillonite at a ratio of 1:1. It has a large specific surface area and strong adsorption performance. After mixing them in a certain proportion, add an appropriate amount of industrial starch. After roasting, the rectorite loses interlayer water. After the industrial starch is burned, the specific surface area of ??the particle adsorption material is increased, and the resistance to heavy metal ions is also enhanced. adsorption performance.
(4) Regeneration test results of granular adsorbent
Table 3 Regeneration test results of rectorite-water quenching slag granular adsorbent material
Table 4 Rectorite -Regeneration test results of fly ash particle adsorption materials
The adsorption saturated particle adsorption materials under the optimal adsorption conditions of the orthogonal test were washed three times with deionized water, dried and then used with different desorbents (HNO3 , HCl, NaCl), conduct a desorption regeneration test, stir for 2 minutes every 2 hours, desorb for 12 hours, and then wash repeatedly with deionized water until there is no Cl- or in the cleaning solution. After drying, conduct the copper smelting industrial wastewater Adsorption treatment, the test results are shown in Table 3 and Table 4.
It can be seen from the table that 1 mol/L NaCl has the best desorption and regeneration effect. The residual concentrations of Cu2+, Pb2+, Zn2+, Cd2+, and Ni2+ in the treated wastewater are still lower than the national comprehensive sewage discharge standard (GB8978-1996). Level standard, the removal rate is very close to the removal rate of newly prepared granular adsorption materials. After desorption and regeneration 6 times, the removal rate is 80% of the new material removal rate, indicating that the prepared granular adsorption materials have better reuse effects.
3. Conclusion
1) The process conditions for the preparation of rectorite-water quenching slag and rectorite-fly ash particle adsorption materials are: rectorite and water quenching slag The ratio of rectorite to fly ash is 1:1, and 10% additive (IS) and 50% water are added. The roasting temperature is 400℃; the ratio of rectorite to fly ash is 1:1, and 15% additive (IS) is added. ) and 50% water, the roasting temperature is 500℃. The particle adsorption material produced not only has good adsorption effect, but also has a low loss rate.
2) The suitable conditions for the removal of heavy metal elements from copper smelting industrial wastewater by rectorite-water quenching slag particle adsorption materials are: under natural pH conditions, the dosage of particle adsorbent is 0.05g/cm3, The reaction time was 40 min, and the temperature was 25°C (normal temperature). Under this condition, the removal rates of Cu2+, Pb2+, Zn2+, Cd2+, and Ni2+ were 98.2%, 96.3%, 78.6%, 86.2%, and 64.2% respectively. The suitable conditions for using rectorite-fly ash particle adsorption materials to remove heavy metal elements from copper smelting industrial wastewater are: under natural pH conditions, the particle adsorbent dosage is 0.07g/cm3, the reaction time is 60 min, and the temperature is 25 ℃ (normal temperature). Under this condition, the removal rates of Cu2+, Pb2+, Zn2+, Cd2+, and Ni2+ are 98.9%, 97.5%, 96.7%, 90.2%, and 79.1% respectively. The residual concentrations of these heavy metal elements in the treated wastewater are lower than the first-level standards of the National Comprehensive Wastewater Discharge Standard (GB8978-1996).
3) Use 1 mol/L NaCl to desorb and regenerate the saturated particle adsorption materials under optimal adsorption conditions, and then use them to treat copper smelting industrial wastewater. The treated wastewater will contain Cu2+, Pb2+, and Zn2+ The residual concentrations of Cd2+ and Ni2+ are still lower than the first-level standard of the National Comprehensive Wastewater Discharge Standard (GB8978-1996), and the removal rate is very close to that when using newly prepared granular adsorption materials. Compared with other adsorbent materials, particle adsorbent materials have the advantages of easy separation, reusability, low cost, and good treatment effect, so they have good application prospects.
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Preparation of clay functional materials and their application in treatment of heavy metal-containing wastewater
Gong Wenqi, Han Pei, Wang Hukun, Liu Yanju, Rao Boqiong
（School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan 430070, Hubei, China)
Abstract: The preparation technological conditions and regeneration method of two novel granulated adsorbing materials of rectorite/fly ash composite (Material 1) and rectorite/water quenched-slag composite (Material 2 ) and the use of them to remove heavy metals from copper smelting plant wastewater have been studied.The experimental results showed that under the preparation conditions with the ratio of rectorite to fly ash or water quenched slag of 1:1, the amount of the additive (Industrial Starch, IS) of 15% (Material 1) or 10% (Material 2), the addition of 50%water, and the calcination temperature of 500℃ (Material 1) or 400℃ (Material 2), the efficiency of heavy metal removal with the granulated materials was the best, whereas the ra tio of disintegration loss was low. Under the treatment conditions of natural pH, and with the addition of the granulated materials of 0.07g/cm3 (Material 1) or 0.05g/ cm3 (Material 2), a reaction time of 60 minutes (Material 1) or 40 minutes (Material 2), and the adsorption temperature of 25℃, the efficiency for the gran ulated materials to remove Cu2＋, Pb2＋, Zn2＋, Cd2＋and Ni2＋from copper smelting plant wastewater was 98.9%, 97.5%, 96.7%, 90.2%and 79.1%(Material 1) or 98.2%, 96.3%, 78.6%, 86.2%and 64.2%(Material 2), respectively, and the quality indexes of the wastewater after treatment conformed with the first level of integrated wastewater discharge standard (GB8978-1996). The granulated materials saturat ed with heavy metal ions on the surface could be regenerated with quite good efficiency by washing with 1 mol/L sodium chloride (NaCl) solution.The granulated adsorbing materials had the advantages of high efficiency in wastewater treatment, easy method of solid-liquid separation and regeneration, and have a broad prospect of applications.
Key words: Rectorite, water quenched-slag , fly ash; granulated adsorbing material, regeneration, copper smelting plant wastewater.