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 increase in cement production as a result of growing demand in the construction sector means an increase in energy consumption and CO₂ emissions. These emissions are estimated at 7% of the global production of CO₂. Ultra-high-performance concrete (UHPC) has excellent mechanical and durability characteristics. Nevertheless, it is costly and affects the environment due to its high amount of cement, which may reach 800–1000 kg/m³. In order to reduce the cement content, silica fume (SF) was utilized as a partial alternative to cement in the production of UHPC. Nevertheless, SF is very expensive. Therefore, the researchers investigated the use of supplementary cementitious materials cheaper than SF. Very limited review investigates addressed the impact of such materials on different properties of UHPC in comparison to that of SF. Thus, this study aims to summarize the effectiveness of using some common supplementary cementitious materials, including fly ashes (FA), ground granulated blast furnace slag (GGBS), metakaolin (MK) and rice husk ashes (RHA) in the manufacturing of UHPC, and comparing the performance of each material with that of SF. The comparison among these substances was also discussed. It has been found that RHA is considered a successful alternative to SF to produce UHPC with similar or even higher properties than SF. Moreover, FA, GGBS and MK can be utilized in combination with SF (as a partial substitute of SF) as a result of having less pozzolanic activity than SF.

The novel aspect of this research is the fabrication, characterisation, and application of an engineered adsorbent made from quartz sand coated with calcium ferric oxides (QS/CFO) derived from the wastepaper sludge ash (WPSA) for the removal of tetracycline (TC) from synthetic water. Initially, the new adsorbent was fabricated using a Ca/Fe molar ratio, sand/FeCl₃ ratio, pH (of synthesising environment), ethylene glycol dose, and temperature of 1:0.75, 1:1, 12, 6 mL/100 mL, and 95 °C, respectively. Then, the new adsorbent was applied to treat water having 50 mg/L of TC in batch experiments, taking into account the effects of the contact time (0–180 min), pH of water (2–12), the dose of adsorbent (0.05–0.5 g), and agitation speed (0–250 rpm). The results obtained proved the engineered adsorbent can remove as much as 90% of the TC (adsorption capacity of 21.96 mg/g) within 180 min at an initial pH, adsorbent dosage, and agitation speed of 7, 0.3 g per 50 mL, and 200 rpm, respectively. It was also found that the pseudo-second-order model describes the kinetic measurements better than the pseudo-first-order model, which indicates that the TC molecules have been bonded with the prepared sorbent through chemical forces. Furthermore, the intra-particle diffusion model results demonstrated that the diffusion mechanism plays a significant role in TC adsorption; however, it was not the predominant one. Finally, the outcomes of the characterisation analysis proved that the newly formed layer on the quartz sand substantially contributed to the removal of the TC from the contaminated water.

A new green reactive adsorbent (calcium ferric oxide silica sand (CFO-SS)) made from wastepaper sludge ash and ferric ions was synthesised and shown to remove tetracycline antibiotics (TC) from contaminated water effectively. The synthesised sand was dried at 95 °C, and a series of batch and fixed bed experiments were performed to determine the optimum operating conditions. Results showed that the adsorption capacity of the CFO-SS increases with the concentration gradient between the solid and liquid phases. 0.3 g of the new adsorbent was proven sufficient to remove more than 90% of the TC at a pollutant dose of 50 mg/L in 50 mL of simulated groundwater with an agitation speed of 200 rpm for 3 h. The adsorption isotherm followed the Langmuir isotherm model, with a loading capacity of 21.96 mg/g at pH 7, while the Pseudo second-order model best described the absorption kinetics. The adsorption mechanisms proposed included electrostatic interaction, intraparticle diffusion, hydrogen bonding, and cation-π interactions. Characterisation investigations revealed that the newly precipitated oxides on silica sand play an essential role in TC adsorption support. In fixed-bed experiments, it was discovered that reducing the flow rate and inflow concentration of TC and increasing the sorbent mass significantly extended the lifetime of the produced sorbent in the packed column. The measured breakthrough curves were best fit with the Adams-Bohart and the Clark models, as they provided the highest square root number (R²) values. Finally, considering the efficacy of CFO-SS in TC adsorption performance, it can be noted that the novel synthesised reactive material is an efficient and environmentally friendly material for TC removal, and it presents a potential solution to resolving the challenge of TC-rich groundwater.

This study addresses the significant environmental challenge of pharmaceutical pollutants by demonstrating the effectiveness of a hybrid electrocoagulation–adsorption (EC-A) technique for removing Montelukast Sodium (MS) from contaminated water. The research was conducted in three stages—adsorption, electrocoagulation, and adsorption using the residual water from the electrocoagulation process. The adsorbent materials were characterised using various analytical techniques: X-ray Diffraction (XRD) for determining the crystalline structure, Energy-Dispersive X-ray Spectroscopy (EDX) for elemental composition, Scanning Electron Microscopy (SEM) for surface morphology, and Fourier Transform Infrared Spectroscopy (FTIR) for identifying functional groups before and after interaction with the pollutants. The adsorption phase achieved optimal results at a pH of 3 and a contact time of 120 min, with a maximum removal efficiency of 99.5% for a starting MS concentration of 50 mg/L using Calcium Ferric Oxide–Silica Sand (CFO-SS) adsorbent. The electrocoagulation phase showed a 97% removal efficiency with a pH of 11, a current density of 20 mA, and a 5 mm electrode distance, achieved in just 20 min. Finally, the combined EC-A process, with the pH of residual water adjusted to 3, further enhanced the removal efficiency to 74%, highlighting the method’s potential for pharmaceutical contaminant removal. These findings underscore the potential of the EC-A technique as a highly effective and adaptable solution for mitigating pharmaceutical contaminants in water.

This study investigates the effectiveness of using Iraqi clay as a low-permeability layer to prevent the migration of lead and nickel ions in groundwater-aquifers. Tests of batch operation have been conducted to determine the optimal conditions for removing Pb²⁺ ions, which were found to be 120 minutes of contact time, a pH of 5, 0.12 g of clay per 100 mL of solution, and an agitation of 250 rpm. These conditions resulted in a 90% removal efficiency for a 50 mg L⁻¹ initial concentration of lead ions. To remove nickel ions with an efficiency of 80%, the optimal conditions were 60 minutes of contact time, a pH of 6, 12 g of clay per 100 mL of solution, and an agitation of 250 rpm. Several sorption models were evaluated, and the Langmuir formula was found to be the most effective. The highest sorption capacities were 1.75 and 137 mg g⁻¹ for nickel and lead ions, respectively. The spread of metal ions was simulated using finite element analysis in the COMSOL multiphysics simulation software, taking into account the presence of a clay barrier. The results showed that the barrier creates low-discharge zones along the down-gradient of the barrier, reducing the rate of pollutant migration to protect the water sources.