Magnetic iron oxide/kaolinite (MK) composite was synthesized using co-precipitation method and characterized by XRD, FTIR, SEM/EDX, TGA, XPS, VSM, and zeta potential analyses. The synthesized composite consisting of kaolinite halloysites with small clusters of iron oxide on its outer surface was used in batch experiments to adsorb Congo red dye at different temperatures. The adsorption data were fitted to three different isotherms with Langmuir adsorption isotherm best fitting the adsorption data. The maximum adsorption capacity of MK adsorbent was found to be around 45.59 mg/g. Adsorption kinetics data obtained at three different temperatures were fitted to pseudo-first-order and pseudo-second-order models, where the latter model was able to better interpret the obtained kinetics data with a pseudo-second-order rate constant of 8.60 × 10−2 g.mg−1.min−1. Further analysis of the kinetic data revealed that the adsorption mechanism could be explained via intraparticle diffusion model. Thermodynamic parameters ΔG°, ΔH°, and ΔS° for the adsorption process were determined with the results revealing the adsorption process to be favorable, endothermic, and physical in nature. Finally, comparison with other adsorbents showed that the synthesized MK composite exhibits significant potential to be used as an adsorbent for the removal of organic pollutants from aqueous solutions.

Elevated arsenic levels in soil and water resources due to improper waste management by industry cause detrimental impacts on the environment and human health due to its carcinogenicity and high toxicity. This work demonstrated a facile and scalable method for the synthesis of γ-Fe2O3-PEG-PPG-PEG composites for practical arsenic adsorption. The synthesis of γ-Fe2O3-PEG-PPG-PEG composites resulted in a high percentage yield of 91.4%. Morphological analyses confirmed the microstructures and crystallinity of γ-Fe2O3-PEG-PPG-PEG composites. Besides, HR-TEM showed a homogeneous distribution of γ-Fe2O3 nanoparticles with an average particle size of 25 nm. The peak at 452 cm−1 in FT-IR spectra corresponds to the Fe–O stretching vibration, thus confirming the presence of γ-Fe2O3 nanoparticles. The synthesized composites showed increasing surface area (31–117 m2/g) and thermal stability with increasing γ-Fe2O3 nanoparticle compositions. The As(V) batch adsorption study revealed efficient As(V) removal up to 56.5 µg/g determined by the Langmuir adsorption isotherm. Furthermore, the equilibrium adsorptions were attained between 30 and 120 min. Notably, the adsorption capacity of the γ-Fe2O3-PEG-PPG-PEG composites increased significantly as the As(V) initial concentration increases. The research findings showed that the γ-Fe2O3-PEG-PPG-PEG composites could be potential adsorbents to treat arsenic-contaminated wastewater. Besides, the synthesized composites were proven to be economical and practical for scaling up due to their high product yield.

It is well accepted that moisture ingress in concrete reduces durability and life span of water assets. Condition assessment is an important tool to inform decision for maintenance, retrofit or replacement. However, the most significant challenge is to obtain accurate condition information, particularly when the inspection points are physically difficult to access or inaccessible. Therefore, a reliable and cost-effective monitoring (sensor) system, preferably real-time with ability to streaming online, would be a useful management tool, particularly for water utilities. This paper describes an approach to develop a distributed optical fibre humidly sensor for condition assessment and environmental monitoring both inside and outside of infrastructures, such as inside the concrete and surrounding soil. A new polyelectrolyte multilayer (PEM) coating with higher sensitive was evaluated for relative humidity measurement in soil and concrete, respectively. In this study, two simulated conditions, in concrete and soil, were conducted to evaluate the sensing concept with the development of appropriate measuring methodologies including fibre installation and protection. The optical fibre sensor setup in laboratory environment showed that optical sensor can detect and indicate voltage change with the variation of moisture contents in both soil and concrete. The test results indicate a good correlation between high levels of relative humidity/moisture and transmitted optical power. A simple relative humidity (RH) calibration can be used to convert signal to RH in percentage for soil and concrete measurements and the procedure used to imbed the fibre in both samples is effective. Nevertheless, the sensor measures soil humidity (not moisture content); therefore, further investigation is required to identify the consequence for the variation of the measured parameter.