This work used a variety of experimental studies to explore the elimination of cadmium and lead ions from aqueous solutions using a novel method for the biosynthesis of nanoparticles of zinc oxide sorbents (ZnO-NPs) from mangrove leaf extract. The influences of important factors affecting the adsorption technique were determined, including the pH value, contact duration, the initial concentration of metal ions, nano-adsorbent dose, different temperatures, and interfering ions. To confirm the formation of synthesized ZnO NPs and validate the properties of green-synthesized sorbents, a variety of analytical methods were used, including UV–vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The results showed that the average diameter of the ZnO-NPs was approximately 29.1 nm (spherical at the nano-size regime). The adsorption reaction rate was examined by comparing pseudo-second order against pseudo-first order templates. From the observed records, the adsorption reaction of Cd²⁺ and Pb²⁺ on the ZnO-NPs fitted well with the pseudo-second order template. Freundlich, Langmuir, Dubinin–Radushkevich, and Tempkin equilibrium isotherm models were used to evaluate the sorption of Cd²⁺ and Pb²⁺ onto the sorbent material. Based on the parameters extracted from each model, as well as the model-fitting values, the preferential isotherms for Pb²⁺ and Cd²⁺ ion adsorption on ZnO-NPs were the Dubinin–Radushkevich and Langmuir models, respectively. ZnO-NPs have the potential to be used as an effective and promising adsorbent material for eliminating metal ions from water solutions.

Chromium (Cr) ion is regarded as a particularly hazardous contaminant due to its high toxicity and potential carcinogens. The Cr⁶⁺ ions were removed in the current work using a new fabricated low-cost adsorbent called Pea pods biochar-NH₂ (PBN). PBN was characterized using BET, BJH, SEM, FTIR, TGA, DSC, XRD, XPS and EDX. The surface area and the pore size of PBN were decreased due to the amination process on the pea pods’ biochar-H₂O₂ (PBO). Optimized condition of different parameters of Cr⁶⁺ ions adsorption by PBN was observed at the pH 1.5, contact time (180 min), starting concentration (100 mg/L), and 0.1 g of PBN. The maximal adsorption capacity (Q_m) of PBN is 384.62 mg/g. Different error models were used to test the isotherm models’ results. The mechanism of the adsorption was proposed based on the XPS analysis. The adsorption process had an R² value of 0.999 as the best fit with the Freundlich isotherm (FIM) and pseudo-second-order kinetic (PSOM) models. These obtained data explored that the generated PBN can be a novel, cost-effective material for the adsorption of Cr⁶⁺ ions from an aqueous solution.

Marine sediment samples were collected along the Jeddah coast, Red Sea, Saudi Arabia, in order to assess radiation hazards and the exposure to human and marine living organisms. Using collaborative techniques, grain size, mineralogical characteristics, and natural radioactivity were investigated. To examine the influence of sediment characteristics over the distribution of the measured radionuclides, resulting data were statistically processed by using multivariate analyses. ²³⁸U, ²³²Th, and ⁴⁰K levels were specified to be 19.50, 9.38, and 403.31 Bq kg⁻¹, respectively. Radionuclides distributions were affected by sediment mud content, organic matter, and heavy minerals index. The calculated radiation risk parameters are within the safe range and lower than the global average. Natural radiation from these marine sediments is normal and poses no significant radiological risk to the public or marine living organisms. The natural radioactivity of the marine sediment in this Jeddah coastline will have to be monitored on a regular basis to avoid overexposure to the residents.

In this study, eighteen sites at Jeddah coastal area, Red Sea, have been assessed for water quality status, depending on nutrients, metals, Chlorophyll-a (Chl-a) and physical variables during 2018 and 2019. The investigated parameters of the Water Quality Index (WQI) are temperature, pH, salinity, dissolved oxygen (DO), DO saturation, oxidizable organic matter (OOM), suspended particulate matter (SPM), Chl-a, ammonium, nitrite, nitrate, total nitrogen, reactive phosphate, total phosphorus, silicate, Zn, Fe, Mn Cu, Cd, Pb, and Ni. The results revealed that the pH values were slightly alkaline with a range of 7.85–8.20. The results of other parameters were as follow: salinity (36.95–42.61PSU), DO (5.22–6.67 mg/L), OOM (0.40–1.23 mg/L), SPM (12.39–21.5 mg/L), Chl-a (0.10–0.83 µg/L). The range of nutrients (μM) were 0.07–0.22, 0.45–1.47, 9.62–18.64, 23.31–57.65, 0.05–0.15, 0.55–2.78 and 2.54–5.51 for NH4/N, NO2/N, NO3/N, TN, PO4/P, TP and SiO4/Si, respectively. Cluster analysis was used to classify the stations studied. From the current study, five clusters were found, indicating the need to perform cluster analysis in the water quality assessment process to confirm the durability and consistency of the data discovered in the current application.

This study investigates the potential of pure chitosan powder as an effective, sustainable, and low-cost adsorbent for the removal of synthetic dyes from aqueous media. The work demonstrates the potential of pristine chitosan for practical wastewater treatment applications by adsorbing two commonly used textile dyes, methyl orange (MO) and methylene blue (MB). To elucidate the adsorption mechanism, chitosan was comprehensively characterized using zeta potential analysis, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy (SEM–EDX), Thermogravimetric Analysis (TGA), Brunauer–Emmett–Teller (BET) surface area analysis, and point of zero charge (pHpzc) determination. FTIR analysis revealed notable shifts in –NH₂ and –OH functional groups after dye adsorption, confirming their involvement in electrostatic interactions and hydrogen bonding with MO and MB. SEM images demonstrated significant surface morphological changes following adsorption, while EDX spectra confirmed successful dye uptake through the appearance of sulfur and nitrogen signals characteristic of MO and MB, respectively. Zeta potential and pHpzc results explained the strong pH-dependent adsorption behavior, highlighting favorable electrostatic attraction between chitosan and the ionic dyes. The optimum adsorption conditions were achieved at adsorbent dosages of 0.5 g for MO and 1.0 g for MB, a contact time of 30 min, initial dye concentrations of 20 and 100 mg/L, and solution pH values of 3 for MO and 9 for MB at room temperature. The adsorption data fit the Langmuir isotherm model, indicating monolayer adsorption on a homogeneous chitosan surface, with maximum adsorption capacities of 7.843 mg/g for MO and 7.605 mg/g for MB. Kinetic studies showed that adsorption followed the pseudo-second-order model, suggesting chemisorption as the dominant mechanism. Thermodynamic analysis indicated that the adsorption process was endothermic and non-spontaneous under the investigated conditions. In conclusion, these findings demonstrate that unmodified chitosan is a practical, eco-friendly adsorbent for dye removal, achieving removal efficiencies comparable to many modified chitosan composites, and represents a promising candidate for sustainable wastewater treatment.