We aimed to obtain magnesium/iron (Mg/fe)-layered double hydroxides (LDHs) nanoparticlesimmobilized on waste foundry sand-a byproduct of the metal casting industry. XRD and ft-iR tests were applied to characterize the prepared sorbent. The results revealed that a new peak reflected LDHs nanoparticles. In addition, SEM-EDS mapping confirmed that the coating process was appropriate. Sorption tests for the interaction of this sorbent with an aqueous solution contaminated with congo red dye revealed the efficacy of this material where the maximum adsorption capacity reached approximately 9127.08 mg/g. The pseudo-first-order and pseudo-second-order kinetic models helped to describe the sorption measurements, indicating that the physical and chemical forces governed the removal process. The severity of water pollution has been resulted from the economic development adopted by human overall the world. The different industries such as textile, plastic, coating, and paper utilize the "dyes" in the different manufacturing stages 1-3 These compounds, even at extremely low concentrations can cause a significant contamination and, consequently, the destroying of the ecosystem elements 4-6. The continuous discharge of water contaminated with poisonous dyes to the environment can be formed a potential threat to the aquatic life and human health especially that the dyes are intrinsically toxic 7,8. Therefore, economical and highly efficient techniques need to be developed for treatment of the contaminated water 9-11. The presently available techniques include photocatalysis 12 , biodegradation 13 , chemical coagulation 14 , ion exchange 15-17 , and adsorption 18-22. The adsorption is one of the most valuable methods in the treatment of the aqueous solutions because of its high efficiency, ease of operation, low cost of operation, and easy desorption 23-25. The selection or fabrication of the adsorbents is the main operative point of adsorption, where these materials must be highly stable, low cost, environment-friendly, and definitely efficient 26,27. Until date, literatures have been reported different reactive materials containing activated carbon, zeolite, clay, chitosan, montmorillonite, and vermiculite 7. However, several disadvantages of these materials include the high cost, poor adsorption capacity, and low reuse rate, which limits their usage 28,29. Thus, finding more efficient, longer durability and low cost new adsorbents are a difficult but a vital task. Layered double hydroxide (LDH) is a type of layered anionic compound that is joined via a non-covalent bond-an interaction between non-framework interlayer anions and positively charged main lamellar. Its general formula is [M +2 1-x M +3 × (OH) 2 ] x + [An − x/n •mH 2 O] x − , where, M +3 is a trivalent metal ion such as Fe +3 , Cr +3 , Sc +3 , and Al +3 ; M +2 is divalent metal ions such as Mn +2 , Mg +2 , Ni +2 , and Zn +2 ; An − is an anion that balances the interlayer charge such as Cl − , OH − , NO 3 − , and CO 3 −2 ; x is the ratio of M +3 / (M +3 + M +2), var...

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The present study modifies the sorption isotherm for simulating the influences of initial pH and temperature variations on the cadmium sorption from contaminated water using waste foundry sand based on Langmuir, Freundlich, and Temkin models. Results proved that the Langmuir expression is able to adopt these effects by relating sorption capacity and affinity constants with pH and temperature of aqueous solution through exponential relationships (determination coefficient = 0.9375). The present model is assumed that the sorption process occurs through acidic functional groups and this is consistent with FTIR outputs. Interaction of cadmium/WFS is found to be exothermic by thermodynamic analysis.

The present study investigated the removal efficiency of ammonia nitrogen from simulated wastewater by waste foundry sand based on 120 batch experiments which were modeled by three-layer artificial neural network technique. Contact time (5-120 min), pH of the aqueous solution (3-10), concentration (400-600 mg/L), sorbent dosage (20-120 g/100 mL) and agitation speed (50-250 rpm) were studied. Results showed that the best values of the above parameters were time of  90 min, pH= 10, 400 mg/L, dosage of 90g/100 mL and 200 rpm respectively with removal efficiency equals to 95%. The sorption process was described in a good manner using ANN model which consisted of the tangent sigmoid and linear transfer functions at hidden and output layers respectively with 8 neurons and the maximum sorption capacity was 0.9 mg/g. The sensitivity analysis signified that the relative importance of contact time equal to 36.9% and it is the influential parameter in the sorption of ammonia nitrogen. However, the relative importance of other parameters was agitation speed of 27.43%, WFS dosage of 17.32%, pH of 9.86% and initial concentration of 9.39%.

The present study develops the sorption model for simulating the effects of pH and temperature on the uptake of cadmium from contaminated water using waste foundry sand (WFS) by allowing the variation of the maximum adsorption capacity and affinity constant. The presence of two acidic functional groups with the same or different affinity is the basis in the derivation of the two models; Model 1 and Model 2 respectively. The developed Bi-Langmuir model with different affinity (Model 2) has a remarkable ability in the description of process under consideration with coefficient of determination > 0.9838 and sum of squared error < 0.08514. This result is proved by FTIR test where the weak acids responsible of cadmium ions removal using WFS sorbent can be represented by surface silanol (O-H) functional groups.