The removal of Pb(II) and Cu(II) ions by using marine red macroalgae (Gracilaria changii) as a biosorbent material was evaluated through the batch equilibrium technique. The effect of solution pH on the removal of metal ions was investigated within the range of 2–7. The response surface methodology (RSM) technique involving central composite design (CCD) was utilised to optimise the three main sorption parameters, namely initial metal ion concentration, contact time, and biosorbent dosage, to achieve maximum ion removal. The models’ adequacy of response was verified by ANOVA. The optimum conditions for removal of Pb(II) and Cu(II) were as follows: pH values of 4.5 and 5, initial concentrations of 40 mg/L, contact times of 115 and 45 min, and biosorbent dosage of 1 g/L, at which the maximum removal percentages were 96.3% and 44.77%, respectively. The results of the adsorption isotherm study showed that the data fitted well with the Langmuir’s model for Pb(II) and Cu(II). The results of the adsorption kinetic study showed that the data fitted well with the pseudo-second order model for Pb(II) and Cu(II). In conclusion, red alga biomass exhibits great potential as an efficient low-cost sorbent for removal of metal ions.

Hitherto, a considerable amount of research has been carried out to investigate the equilibrium condition of adsorption process; nevertheless, there is no comprehensive study to evaluate the surface adsorption properties of MOFs. Therefore, the adsorption mechanism and equilibrium capacity of MOFs have not been fully understood. Furthermore, the mass transfer mechanism is still unknown and so it is not possible to predict the adsorption process using MOFs. In this work, a new metal–organic framework (MOF) named UIO-66–MnFe₂O₄ was synthesized as an adsorbent for oily wastewater treatment. In this way the effects of temperature, amount of adsorbent, adsorption time, pH, and pollutant initial concentration were studied in the treatment of oily wastewater using the UIO-66-MnFe₂O₄ MOF through the adsorption process. Furthermore, to examine the process of surface adsorption, different adsorption kinetic models (pseudo-first-order, pseudo-second-order, and Elovich) have been performed for the removal of oily pollutants on MOF adsorbents and the surface adsorption mechanism has been discussed carefully. Moreover, to investigate the mass transfer mechanism of oily pollutants in the surface adsorption process, different mass transfer models (Weber and Morris, liquid film diffusion, and Bangham and Burt) have been investigated on porous adsorbents, and finally the mass transfer mechanism of the adsorption process has been proposed.

Activated carbon obtained from red algae Gracilaria changii was used as an adsorbent to remove Pb (II) and Cu (II) from an aqueous solution. The raw red algae were first impregnated with phosphoric acid, followed by thermal activation. The Box–Behnken design was used to optimize the activation process. The optimum activation parameters were 84%, 650 °C, and 175 min for acid concentration, activation temperature, and activation time, respectively. The obtained activated carbon had a high surface area of 867 m²/g. The removal of Pb (II) and Cu (II) was evaluated using a batch adsorption study. The effect of solution pH on the removal of metal ions was investigated within the range of 2–7. The effect of three important adsorption parameters (initial metal ion concentration, adsorbent dosage, and contact time) was analyzed using central composite design. The optimum removal of Pb (II) and Cu (II) was 76% and 36%, respectively. The adsorption kinetics obeyed the pseudo-second-order model, while the adsorption isotherm obeyed the Langmuir model.

This study assessed the quality of water in the Shatt Al-Hillah River by adopting some variables of physical, chemical, and heavy metal elements. The samples have been taken at six sites along the river in 2020 (from January to December). The water quality index has been determined by using the weighted-arithmetic method which is including a series of equations. Also, the model of Inverse-Distance-Weighting in the Geographic information system was applied to create a map of the water quality in the study area. Eleven physicochemical variables and five elements of heavy metals were comprised of calcium, magnesium, dissolved oxygen, Hydrogen Ions, chloride, sulfate, total hardness, total dissolved solids, turbidity, alkalinity, electric conductivity, cadmium, copper, iron, lead, and zinc. The results showed the values of the water quality index ranged from 245 to 253 (with a category of 200–300). The water quality index was rated as very poor for the selected locations along the Shatt Al-Hillah River. The GIS result illustrated the distributing map of water quality for the Shatt Al-Hillah River for household uses. The combination of the water quality index calculations with GIS in the current study might be used as a guide for future studies.

Red algae-derived activated carbon was evaluated for its ability to remove lead (Pb) from synthetic aqueous solution. The activated carbon was prepared at a constant temperature of 300°C for 1 hour using a muffle furnace. Effect of pH contact time, initial ions concentration, and activated carbon dosage as important operating variables on the reaction process were also investigated. The batch experiment was conducted for adsorption experiment. The maximum lead uptake capacity was obtained at pH 6 and operation time of 30 min. the maximum uptake capacity of Pb (II) was found to be 0.1 mg/g. This work confirms the potential use of red algae Gracilaria changii for the removal of heavy metals from wastewater.