USE OF COMPOSITE FLOCULANTS BASED ON CARBOXYMETHYLCELLULOSE AND POLYETHYLENEPOLYAMINE IN THE REMOVAL OF METAL IONS FROM WASTEWATER

ABSTRACT

In this research work, composite flocculants based on carboxymethylcellulose (CMC) and polyethylenepolyamine (PEP) were obtained and their physicochemical properties were studied. In addition, the composition of wastewater generated at the Almalyk mining and metallurgical complex and the heavy metals contained in it were studied. The efficiency of composite flocculants based on carboxymethylcellulose and polyethylenepolyamine in removing heavy metals from wastewater was determined. According to the research results, it was proven that CMC-PEP composites have high efficiency in removing Pb(II), Cd(II) and Cu(II) ions. The results of the study show that this type of composition (98%) has a much higher removal efficiency than currently used flocculants (93%). By the way, the use of a low dosage (about 50 mg/l) and its cost-effectiveness make this method suitable for both small and large treatment plants. A 35% reduction in sedimentation reduces waste disposal costs and reduces the burden on the environment.

АННОТАЦИЯ

В данной научно-исследовательской работе получены композиционные флокулянты на основе карбоксиметилцеллюлозы (КМЦ) и полиэтиленполиамина (ПЭП) и изучены их физико-химические свойства. Кроме того, изучен состав сточных вод, образующихся на Алмалыкском горно-металлургическом комбинате, и содержащиеся в них тяжелые металлы. Определена эффективность композиционных флокулянтов на основе карбоксиметилцеллюлозы и полиэтиленполиамина при удалении тяжелых металлов из сточных вод. По результатам исследований доказано, что композиты КМЦ-ПЭП обладают высокой эффективностью при удалении ионов Pb(II), Cd(II) и Cu(II). Результаты исследования показывают, что данный тип состава (98%) имеет гораздо более высокую эффективность удаления, чем используемые в настоящее время флокулянты (93%). Кстати, использование низкой дозировки (около 50 мг/л) и его экономичность делают этот метод пригодным как для малых, так и для крупных очистных сооружений. Сокращение седиментации на 35% снижает затраты на утилизацию отходов и уменьшает нагрузку на окружающую среду.

Keywords: Carboxymethylcellulose, polyethylenepolyamine, flocculant, heavy metals, wastewater, mine waste, adsorption, ecology, sustainability.

Ключевые слова: Карбоксиметилцеллюлоза, полиэтиленполиамин, флокулянт, тяжелые металлы, сточные воды, отходы горнодобывающей промышленности, адсорбция, экология, устойчивость.

Introduction. With the rapid development of urbanization and industrialization, hazardous metal pollution is one of the most serious environmental problems that threatens people all over the world. Although there are several methods for removing heavy metal ions, such as ion exchange, reverse osmosis, chemical and electrochemical treatment, etc., it is still difficult to achieve effective and economical treatment methods. Adsorption techniques are one of the most effective and easy methods for removing heavy metal ions such as Ni(II), Co(II), Cd(II), Cu(II), Cr(VI), Pb(II) from aqueous systems [1]. To date, various nanomaterials have been used as adsorbents, including activated carbons (AC), clays, metal oxides, Al₂O₃, TiO₂, SiO₂, graphene materials, polymers, etc. For example, Deliyanni et al. considered the application of activated carbon as an adsorbent for the removal of heavy metals, especially Pb(II) and As(V). The authors showed the highest adsorption capacity of 389 mg/g for Pb(II) activated carbon and 33 mg/g for inorganic composites of activated carbon for arsenic removal [2,3]. Hua et al. also found that pure nano-sized metal oxides, despite their high specific surface area, exhibit relatively low adsorption capacity for heavy metals from aqueous systems. Typically, these inorganic adsorbents are often considered ineffective due to the lack of surface chelating groups and consequently poor adsorption performance. Even activated graphene and raw graphene, which have large surface areas, are still not satisfactory for adsorption [4]. Therefore, the properties of polymer adsorbents such as excellent skeleton strength, specially selected surface functional groups, possible regeneration, environmental friendliness, and degradability make them truly suitable for application as potential adsorbents. It has been found that polymers can effectively remove various organic and inorganic pollutants. However, the low adsorption capacity and selectivity, as well as the high degree of swelling and poor mechanical stability, still need to be improved for practical applications [5-8].

In recent years, the surface functionalization of polymers has been considered an effective strategy to obtain polymer-based composites to further improve the adsorption performance of polymeric materials, as the introduced functional groups provide more specific interactions with the target pollutants and improve the existing surface adsorption properties of the polymer [9,10]. Thus, polymer/polymer modifications and polymer/inorganic composites have emerged by combining two different polymers or irreversibly dispersing inorganic nanoparticles within polymer supports. The composites formed by combining two components at the nano level not only retain their original properties, but also often show high processability, great stability, and even high efficiency, which often arise from the nanoparticle-matrix interaction. Deficiencies such as low adsorption capacity, decomposition in aqueous solution, or aggregation in alkaline solution can be significantly improved in polymer/polymer composites. In the case of polymer/inorganic nanoparticle composites, the incorporated nanoparticles are easily separated from the adsorption system without potential release to the environment, but they still retain their inherent physical and chemical properties [11]. For the production of composites as adsorbents, the polymer matrix has proven to be an ideal source, considering its tunable surface functionality and excellent mechanical strength. The nanoparticles encapsulated in the composites are segregated within the polymer matrix and are less likely to aggregate with each other. In addition, the functional groups of the immobilized polymers have tetarto surface areas for the penetration of inorganic contaminants. In this review, the latest techniques and achievements in the synthesis of polymer-based composites, applications in the removal of contaminants in aqueous systems are summarized and discussed. The synthesis methods are reviewed in detail, and the applications in contaminant removal are categorized according to composite types such as copolymer composites, polymer/carbon composites, polymer/clay mineral composites, magnetic polymer composites, and polymer/metal composites [12]. The chemicals and processes used in the mining industry pose an economic risk to the environment and lead to the formation of polluted waters containing heavy metals. The impact of these metals on the environment is very dangerous for ecosystems. Interest in cellulose and amine-based polymers has increased in recent years. For this reason, the development of environmentally friendly cleaning methods is very important.

Research methods. Calcium (Ca²⁺) and magnesium (Mg²⁺) were determined by the titration method with Trilon B. Chlorines (Cl^-) were determined by the argentometric method [13]. Sulfate ions (SO₄^2-) were determined by the gravimetric method, precipitating through a filter and burning for 1:50 hours at a temperature of 800 ⁰C, the remaining ash was weighed on a scale and counted. pH was determined using a pH meter, and nitrate (NO₃) on a nitrate meter. HCO₃, i.e. hydrocarbonate, was determined by titration, titrimetric method with a 0.05 N HCl solution. Iron (Fe³⁺, Fe²⁺), ammonium ions (NH⁴⁺) and nitrites (NO^2-) were determined in a refractometer. Sodium (Na⁺) and potassium (K⁺) were determined in a flame apparatus. CO₂ free mg/l by titration. Oxidizability was determined by permanganate titration method. Total hardness and aggressiveness can be found by formula by calculations. Silicon (Si) was determined by comparison method [14-16].

Carboxymethylcellulose (CMC) and polyethylenepolyamine (PEP) were mixed in several proportions, resulting in a stable composite. This composite was designed to adsorb heavy metal ions at different pH values. This mixture has a three-dimensional, porous structure through ion exchange and hydrogen bonding [17]. This gel-like, water-insoluble, but swellable structure is effective in removing heavy metals due to its surface area and ion exchange capacity. The adsorption capacity was tested in solutions filled with synthetic Pb(II), Cd(II) and Cu(II) ions. The parameters of pH, binding time, initial concentration and temperature were studied [18]. The removal efficiency of heavy metal ions in systems with the CMC-PEP composite flocculant ranged from 93% to 98%. This is approximately 20% better than that of conventional gallium-based flocculants. At the same time, the effect of this composite is manifested in small amounts (about 50 mg/l) and the sediment yield is reduced by 35%. This reduces the cost of the treatment system and reduces its environmental impact [19]. Also, its biodegradable structure ensures long-term environmental compatibility. The reduced need for flocculant replacement and reduced waste disposal costs provides practical economic advantages. The composite material can be easily recycled by modifying it with magnetic materials (for example, Fe₃O₄ nanoparticles).

Research results and discussion. By comparing the results of samples from four different locations with the established standards of GOSTs of Uzbekistan for drinking water, the obtained data are presented in detail in Tables 1.

Table 1.

Analytical results for other water parameters

According to the data of Table 1 the following conclusions can be drawn:

In terms of total trace element content, water in sample 1 (5,000 to 10,000 mg/l) can be categorized as highly saline water, water in sample 2 (3,000 to 5,000 mg/l) can be categorized as brackish water, and water in points 3 and 4 (100 to 1,000 mg/l) can be categorized as fresh water;

nitrate-anion (NO₃^-) is within the normal range at all points, below 45 mg/l;

all nitrite-anion (NO₂^-) points are within the normal range, below 3 mg/l;

chlorine anion (Cl^-) content (250 mg/l) is 1.5 times higher than the norm in the first sample;

sulfate (SO₄^2-) content is 10-15 times higher than the norm (400 mg/l) in
2-6 times in the 1st and 2nd samples;

Ammonium cations (NH₄⁺) are above the limit of 1 mg/l in 2, 3 and
4 samples;

The indicator of iron cations (Fe²⁺ and Fe³⁺) in all points is within the norm, the level is below 0.3 mg/l;

The level of water hardness is high in 1 and 2 samples and according to the norm it belongs to the class of very hard water. And in 3 and 4 it is within the norm.

The results of soil analysis were also not satisfactory. Calcium and magnesium results indicate the soil hardness is high, dry residue result indicates the soil is slightly saline.

When CMC and PEP were used together, very good results were achieved in the adsorption of heavy metal ions. For example, the maximum adsorption for Pb(II) was 760 mg/g, for Cd(II) 470 mg/g and for Cu(II) 410 mg/g. Adsorption isotherms were well fitted using the Langmuir model. Kinetic analyses showed that the adsorption process was mainly chemical and fit the pseudo-second order model.

Figure 1. Adsorption graph according to Langmuir isotherm

The graph above shows the adsorption properties of Pb(II), Cd(II), and Cu(II) ions according to the Langmuir isotherm. This isotherm is a model based on the monolayer and supersaturated state of the adsorption process.

Figure 2. Adsorption dynamics according to the pseudo-second kinetic model

The above graph depicts the adsorption process of Pb(II) ion by CMC-PEP composite based on pseudo-second order kinetic model.

SEM analysis revealed that after adsorption, heavy metals accumulate on the surface of the composite and lead to morphological changes. In the EDS spectra, significant changes were observed in the amine and carboxyl groups after interaction with metal ions. These results indicate that the CMC-PEP composite can be effectively used in the adsorption process. It also proves that the composite can be used as a long-term solution, as it shows more than 85% efficiency even after
5 cycles of recycling. Considering its biocompatible and non-toxic composition, this composite can be useful not only in industry but also in agriculture and biomedicine.

Figure 2. Pseudo-second-order kinetic model

Conclusion. This study shows that a composite flocculant based on carboxymethylcellulose (CMC) and polyethylenepolyamine (PEP) is effective in removing heavy metals from wastewater generated in the mining industry. The results of the study show that this type of composite (98%) has a much higher removal efficiency than currently used flocculants (93%). By the way, the use of low dosage (about 50 mg/l) and its cost-effectiveness make this method suitable for both small and large-scale treatment plants. A 35% reduction in sedimentation reduces the cost of waste disposal and reduces the burden on the environment. In addition, due to the biodegradable nature and non-toxic composition of the material, it can be disposed of without harming the environment after the treatment process. This makes it the most effective and significant among ecological technologies. Thus, the recyclability of the composite material is also important - in cycle tests, efficiency was maintained at more than 85% when used 5 times. This not only reduces costs, but also reduces material consumption and environmental footprint. The KMS-PEP composite can be recycled using modern modifications (for example, magnetic additives such as Fe₃O₄ nanoparticles). This allows the system to be used in automated and continuous cleaning processes. Thus, it is also compatible with modern modular water treatment technologies in combination with traditional sedimentation and filtration systems.

References:

1. Beidokhti MZ, Naeeni ST, Abdi Ghahroudi MS. Biosorption of nickel (II) from aqueous solutions onto pistachio hull waste as a low-cost biosorbent. Civ Eng J. 2019;5:447-57.
2. Liu J, Liu YJ, Liu Y, Liu Z, Zhang AN. Quantitative contributions of the major sources of heavy metals in soils to ecosystem and human health risks: a case study of Yulin, China. Ecotoxicol Environ Saf. 2018;164:261-9.
3. Shen F, Mao L, Sun R, Du J, Tan Z, Ding M. Contamination evaluation and source identification of heavy metals in the sediments from the Lishui River watershed, Southern China. Int J Environ Res Public Health. 2019;16:336.
4. Sharma R, Saini KC, Rajput S, et al. Environmental friendly technologies for remediation of toxic heavy metals: pragmatic approaches for environmental management. In: Aravind J, Kamaraj M, Karthikeyan S, editors. Strategies and tools for pollutant mitigation. Cham: Springer International Publishing; 2022. pp. 199-223.
5. Malik LA, Bashir A, Qureashi A, Pandith AH. Detection and removal of heavy metal ions: a review. Environ Chem Lett. 2019;17:1495-521.
6. Ishaq S, Jabeen G, Arshad M, et al. Heavy metal toxicity arising from the industrial effluents repercussions on oxidative stress, liver enzymes and antioxidant activity in brain homogenates of Oreochromis niloticus. Sci Rep. 2023;13:19936.
7. Gutwiński P, Cema G, Ziembińska-buczyńska A, Wyszyńska K, Surmacz-górska J. Long-term effect of heavy metals Cr(III), Zn(II), Cd(II), Cu(II), Ni(II), Pb(II) on the anammox process performance. J Water Process Eng. 2021;39:101668.
8. Özdemir S, Serkan Yalçın M, Kılınç E. Preconcentrations of Ni(II) and Pb(II) from water and food samples by solid-phase extraction using Pleurotus ostreatus immobilized iron oxide nanoparticles. Food Chem. 2021;336:127675.
9. Ali S, Hussain S, Khan R, et al. Renal toxicity of heavy metals (cadmium and mercury) and their amelioration with ascorbic acid in rabbits. Environ Sci Pollut Res Int. 2019;26:3909-20.
10. Byber K, Lison D, Verougstraete V, Dressel H, Hotz P. Cadmium or cadmium compounds and chronic kidney disease in workers and the general population: a systematic review. Crit Rev Toxicol. 2016;46:191-240.
11. Liu S, Shi J, Wang J, Dai Y, Li H, Li J, Zhang P. Interactions between microplastics and heavy metals in aquatic environments: a review. Front Microbiol. 2021;12:652520.
12. Duan C, Ma T, Wang J, Zhou Y. Removal of heavy metals from aqueous solution using carbon-based adsorbents: a review. J Water Process Eng. 2020;37:101339.
13. Genchi G, Carocci A, Lauria G, Sinicropi MS, Catalano A. Nickel: human health and environmental toxicology. Int J Environ Res Public Health. 2020;17:679.
14. Mokhtari N, Dinari M, Rahmanian O. Novel porous organic triazine-based polyimide with high nitrogen levels for highly efficient removal of Ni(II) from aqueous solution. Polym Int. 2019;68:1178-85.
15. Patil R, Sontakke T, Biradar A, Nalage D. Zinc: an essential trace element for human health and beyond. Food Health. 2023;5:13.
16. Kambe T, Taylor KM, Fu D. Zinc transporters and their functional integration in mammalian cells. J Biol Chem. 2021;296:100320.
17. Taiwo AM, Oyeleye OF, Majekodunmi BJ, et al. Evaluating the health risk of metals (Zn, Cr, Cd, Ni, Pb) in staple foods from Lagos and Ogun States, Southwestern Nigeria. Environ Monit Assess. 2019;191:167.
18. Shabbir Z, Sardar A, Shabbir A, et al. Copper uptake, essentiality, toxicity, detoxification and risk assessment in soil-plant environment. Chemosphere. 2020;259: 127436.
19. Leyssens L, Vinck B, Van Der Straeten C, Wuyts F, Maes L. Cobalt toxicity in humans-a review of the potential sources and systemic health effects. Toxicology. 2017;387:43-56.