Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. ICMASD (2025) 1036 https://internationalpubls.com Recent Advances in Removal of Heavy Metals from Aqueous Solution by Gelatin Acrylic Acid-Based Hydrogel - A Review Diksha Bhatt1*, Vaneet Kumar 1, Ramanand Mishra1, Keerti Shrivastava2, Sahilpreet Singh1, Nitika Saini2, Harnoor Kaur2 1 Department of Natural Sciences, CT University, Ferozepur Road, Ludhiana, Punjab, India 2 Department of Biotechnology, CT Group of Institutions, Shahpur, Jalandhar, Punjab, India Article History: Received: 12-12-2024 Revised: 25-01-2025 Accepted: 05-02-2025 Abstract: The contamination of water sources by heavy metals poses significant environmental and health risks, necessitating the development of effective water treatment technologies. This study investigates the potential of gelatin and acrylic acid-based hydrogels for the removal of heavy metals from aqueous solutions. Gelatin, a natural biopolymer, was crosslinked with acrylic acid to form a composite hydrogel, benefiting from both the inherent biocompatibility of gelatin and the ion-exchange properties of acrylic acid. The hydrogel was synthesized through a simple free-radical polymerization method, followed by characterization using scanning electron microscopy (SEM) techniques and swelling studies. The removal efficiency of the hydrogel was evaluated for common heavy metals, including lead (Pb²⁺), mercury (Hg²⁺) and under varying conditions of pH, contact time, and metal ion concentration. Results indicated that the hydrogel exhibited high adsorption capacities for these metals, with the swelling behaviour and ion-exchange interactions enhancing the uptake of heavy metal ions. The hydrogel demonstrated a fast adsorption rate and showed good reusability, making it a promising candidate for sustainable heavy metal removal in contaminated water. This work highlights the potential of gelatin-acrylic acid-based hydrogels as a cost-effective, eco-friendly, and efficient material for environmental remediation. Keywords: contamination, environmental, polymerization, biopolymer. Introduction Heavy metal pollution of water sources is a major environmental concern in the modern day. Metals such as mercury (Hg²⁺), lead (Pb²⁺), cadmium (Cd²⁺) and arsenic (As³⁺) are extremely dangerous to marine life and humans due to their great toxicity and ability to bioaccumulate. Conventional methods of water purification, such as exchange of ions, precipitation from chemicals, and reversible osmosis, can be complex, expensive, and even lead to secondary contamination. In contrast, natural biopolymers, especially hydrogels, have gained increased interest as adsorbents for eliminating heavy metals from polluted water due to their inexpensive cost, high effectiveness, and ecological sustainability [1,2] Hydrogels can be created with the help of gelatin, a biopolymer derived from the animal collagen, because it is safe, sustainable, and naturally compatible with the body [3,4]. Incorporating acrylic acid, an early precursor to synthetic polymers, into the hydrogel mixture enhances its ion exchange Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. ICMASD (2025) 1037 https://internationalpubls.com processes. When purifying water, this component is crucial for removing ions of heavy metals. By incorporating acrylic acid's multifunctional carboxyl groups into the hydrogel matrices, strong interactions involving metal ions are enhanced [5]. This paper summarizes the current state of research in this domain and focuses upon the synthesis, characterization, and utilization of hydrogels composed of acrylic acid and gelatine for facilitating the removal of heavy metals off water solutions. The Development and Evaluation of Hydrogels Based on Acrylic Acid and Gelatin Methods of Synthesis The creation of hydrogels composed of acrylic acid and gelatin typically involves a free-radical synthesis process [6,7]. This process involves the addition of initiators, crosslinking substances, and gelatin to the acrylic acid. Since the approach is suitable for usage in mild conditions, it is attractive for ecological uses. To ensure that the structure of hydrogel maintains its structural integrity throughout the adsorption procedure, it can be crosslinked with an assortment of agents, one of which being N,N'-methylenebisacrylamide [8,9]. 1. Mechanisms of Crosslinking: Hydrogels rely on crosslinking to enhance the stability of their structure. Hydrogels can adsorb more heavy metal ions thanks to the interconnected structure formed by crosslinking substances, which increases the total surface area within the gel [10]. 2. Green Chemistry: The increasing use of green chemistry methods has led to a decrease in the frequency of using toxic chemicals or solvents in the creation of hydrogels [11,12] Methods for Characterization The hydrogels are characterized upon they are produced in order to understand their physical, chemical, and structural properties. 1. Scanning electron microscopy (SEM) It is is employed to examine its outermost layer morphology of the hydrogels. Research indicates that hydrogels made of gelatin and acrylic acid are able to more effectively adsorb metal ions due to their extremely porous nature [13]. 2. Fourier transform infrared spectroscopy (FTIR) It can help identify functional groups within hydrogels. Metal ions can attach to hydrogel by a the exchange of ions process that requires carboxyl (-COOH) as well as hydroxyl (-OH) units from the acrylic acid as well as gelatin, respectively [14, 15]. 3. Studies on Swelling To comprehend the hydrogel's water-absorbing capacity, which influences its heavy metal- absorption capability, one must comprehend its swelling behavior. Ionic strength and pH are examples of such elements [16, 17] Adsorption of Heavy Metals: Hydrogels made of acrylic acid and gelatine eliminate heavy elements through adsorption mostly through ion-exchange linkages. The carboxyl residues of acrylic acid within the hydrogel bind to Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. ICMASD (2025) 1038 https://internationalpubls.com cations made of metals (e.g., Hg2+ and Pb2+) or to substitute molecule of water as well as counter- ions within the gel matrix. Many factors influence the adsorption procedure: The effect of pH The pH level of the solution has a significant impact on hydrogels' capacity to absorb metal ions. Research has shown that the optimal pH for maximum adsorption of certain metals varies. For example, at slightly higher pH levels, lead (Pb²⁺) and mercury (Hg²⁺) show better removal efficiency due to increased ion exchanges [18, 19]. Metal Ion Concentration Affects The effective ability to adsorb is proportional to the concentration of metal ions in the surrounding solution. The ability to absorb may reach a saturation limit where no additional adsorption occurs, even while the motivating factor for metallic ion exchange rises with higher levels of metal ions. [20, 21]. ➢ Contact Period The bulk of metal absorption occurs in the initial several hours, and metallic adsorption typically occurs rapidly thereafter. The equilibrium period required for complete adsorption can be affected by a variety of factors, including the sort of metal ion, hydrogel properties, and environmental conditions [22,23]. ➢ The Endurance and Reusability of Gelatin and Acrylic Acid Hydrogels Hydrogels made of gelatin and acrylic acid have the advantage of being reusable. Renewing these hydrogels is as simple as liberating the adsorption of metals utilising desorption techniques, such as washing with acid or chelating compounds, after each adsorption process. The capacity to reuse adsorbent materials reduces the wastewater treatment procedures overall expenditure [24,25], making it a vital feature for practical applications. However, these hydrogels' ability to maintain stability after multiple adsorption/desorption cycles is an essential component. Hydrogels made of acrylic acid and gelatine have shown to be very stable and with an excellent ability to adsorb even after several cycles of cycling; nevertheless, a small drop in adsorption efficiency could be caused by hydrogel deterioration or functional group leaking [26,27]. Applications for Water Management A variety of heavy metals, including mercury, lead, chromium and cadmium can be efficiently eliminated from water solutions using hydrogels composed of acrylic acid and gelatins. During both laboratory and field tests, these hydrogels showed promising results for real-world uses. Using these gels to treat water has several notable advantages, including: • Environmentally Friendly: Hydrogels, composed of natural biopolymers such as gelatin, offer a non-toxic and biodegradable alternative to traditional methods of eliminating heavy metals [28]. • Efficient Use of Resources: Hydrogels composed of gelatin and acrylic acids are simple to produce, which reduces overall manufacturing expenses. Another inexpensive ingredient is gelatin [29]. High Adsorption Capacity: The hydrogels are useful for cleaning contaminated water since they have high adsorption capacities for a variety of heavy metals [30]. Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. ICMASD (2025) 1039 https://internationalpubls.com Challenges and Prospective Directions Hydrogels made of acrylic acid and gelatins show potential for heavy metallic removal, however there are still many unanswered questions prior to they can be employed extensively: • High-concentration metal solution limitation: When exposed to solutions containing high concentrations of metallic ions, hydrogels may lose some of their adsorption capacity because the available binding sites have become saturated [31,32]. • Consistency over Time: The long-term stability of hydrogels made of gelatin and acrylic acid in harsh environmental conditions is still unknown. 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