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 provision of safe water for people is a human right; historically, a major number of people depend on groundwater as a source of water for their needs, such as agricultural, industrial or human activities. Water resources have recently been affected by organic and/or inorganic contaminants as a result of population growth and increased anthropogenic activity, soil leaching and pollution. Water resource remediation has become a serious environmental concern, since it has a direct impact on many aspects of people’s lives. For decades, the pump-and-treat method has been considered the predominant treatment process for the remediation of contaminated groundwater with organic and inorganic contaminants. On the other side, this technique missed sustainability and the new concept of using renewable energy. Permeable reactive barriers (PRBs) have been implemented as an alternative to conventional pump-and-treat systems for remediating polluted groundwater because of their effectiveness and ease of implementation. In this paper, a review of the importance of groundwater, contamination and biological, physical as well as chemical remediation techniques have been discussed. In this review, the principles of the permeable reactive barrier’s use as a remediation technique have been introduced along with commonly used reactive materials and the recent applications of the permeable reactive barrier in the remediation of different contaminants, such as heavy metals, chlorinated solvents and pesticides. This paper also discusses the characteristics of reactive media and contaminants’ uptake mechanisms. Finally, remediation isotherms, the breakthrough curves and kinetic sorption models are also being presented. It has been found that groundwater could be contaminated by different pollutants and must be remediated to fit human, agricultural and industrial needs. The PRB technique is an efficient treatment process that is an inexpensive alternative for the pump-and-treat procedure and represents a promising technique to treat groundwater pollution.

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.