Abstract The increasing contamination of water bodies by heavy metals, particularly cadmium (Cd²⁺), poses a significant threat to environmental and public health due to its toxicity, persistence, and bioaccumulate nature. This study investigates the potential of citric acid-modified chitosan, derived from oyster shells, as an eco-friendly and cost-effective adsorbent for the removal of cadmium ions from aqueous solutions. Chitosan was extracted through deproteination, demineralization, and deacetylation processes, followed by chemical modification using citric acid to enhance its adsorption properties. Characterization of the modified chitosan was conducted using Fourier Transform Infrared Spectroscopy (FTIR), UV–Visible Spectroscopy (UV–Vis), and Atomic Absorption Spectrophotometry (AAS). FTIR analysis confirmed the successful transformation of oyster shell into chitosan, with the emergence of functional groups such as hydroxyl, carbonyl, and amine groups critical for metal ion binding. UV–Vis. spectroscopy revealed strong absorbance in the UV region and optical transparency in the visible range, indicating high purity and suitability for biomedical and environmental applications. Batch adsorption experiments were performed to evaluate the effects of initial cadmium concentration, contact time, and temperature. The results showed that maximum adsorption occurred at low concentrations, with equilibrium reached at 60 minutes and optimal performance at 40°C. Isotherm modeling revealed that the Freundlich model (R² = 0.8389) better described the adsorption behavior than the Langmuir model (R² = 0.0245), suggesting multilayer adsorption on a heterogeneous surface. Kinetic studies indicated that the pseudo-second-order model (R² = 0.9738) best fit the data, implying chemisorption as the dominant mechanism. Overall, the study demonstrates that citric acid-modified chitosan is a promising biosorbent for cadmium removal, offering a sustainable solution for wastewater treatment. Further optimization and real-world application studies are recommended to enhance its practical viability.

Abstract The global issue of inadequate access to water supply affects more than 850 million people, while over 2.5 billion individuals face limitations in accessing sanitation facilities (WHO and UNICEF, 2014). Recognizing the importance sufficient sterilizations, clearness and safe water Improved sanitation reduces health system costs and leads to fewer days lost at work or school, decreased queue times at shared sanitation facilities, and the elimination of open defecation. This study used by cross- sectional study this means the sample was selected from the target group, and information was obtained simultaneously at a particular point in time. The study result concluded that majority 86 (68.4%) of the respondents were male. The highest number of the respondents 94(75.2%) were aged 20– 25 years.  The majority 60(48%) of the respondents were single. The majority 117 (93.6%) of the respondents were university level of Education. According to the business respondents, the majority of the respondent’s 51 (40.8%) student. 108 respondents (86.4%) have the perceived level of knowledge to consider as appropriate for using Aqua Tap, while 17 respondents (13.6%) do not. Aqua Tap is one of the technologies in water treatment, and given that respondents need to choose from various technologies, high knowledge of Aqua Tap indicates good availability and awareness of this particular technology. Highest number of the respondents 104 (86%) said yes there is serious problems that can cause poor water sanitation. The specialists dove into and underscored angles, for example, research configuration, target populace, test size, inspecting procedures, research instruments, information assortment, information examination, legitimacy and dependability, moral contemplations, and test outline. This study was a cross-sectional review. This implies that the example was chosen from the objective gathering, and data was gotten all the while at a specific moment.