No / This study aims to examine the potential of natural clay mineral from the southern part of Saudi Arabia as an effective adsorbent material for the removal of heavy metal ions of cadmium (Cd) and nickel (Ni) from aqueous solutions. The SEM analysis showed that clay particles had mixed shapes such as elongated rod-like and rectangular shape having rough corners with larger particles of 2-8 µm in size and smaller particles in the sub-micron size range. X-ray diffraction data revealed that clay particles had a good crystalline structure and composed of a mixture of various minerals including feldspar, illite, quartz, calcite, and gypsum. The BET surface area was found to be 35 ± 1 m ² /g and the average pore size and pore volume of 6.5 ± 0.5 nm and 5.7e-02 cc/g, respectively. The X-ray fluorescence analysis of clay showed main compounds of SiO₂ (47.33%), Al₂O₃ (18.14%), Fe₂O₃ (15.89%) with many others such as CaO, MgO, TiO₂, and K₂O in minor quantities. It was found that 1.2 g of clay removed up to 99.5% of Ni and 97.5% of Cd from 40 ppm aqueous solutions. The metal removal efficiencies were increased from around 95% up to 99% by increasing the pH of aqueous solutions from 4 to 11. The adsorption of Ni and Cd ions on Saudi clay was relatively fast, and up to 97% of ions were removed from solution within 45 min. The SEM-EDX and BET analysis for recycled clays further confirmed that the metal ions were removed from water through adsorption onto the clay. The experimental data fitted well with Langmuir and Freundlich isotherms. The maximum adsorption capacity of clay for Cd and Ni from isotherms was found to be 3.3 and 2.7 mg/g respectively. The findings of this study confirm the potential role of Saudi natural clay in wastewater treatment processes as a cheap, environment-friendly and safe natural adsorbent material. / The authors extend their appreciation to the Deanship of Scientific Research at King Khalid University for funding this work through research groups program under grant number R.G.P1./97/40.

An increasingly recognized problem in the world is stormwater runoff and its generation of pollutants in urban areas. Stormwater treatment technologies have therefore increased in implementation to prevent this pollution. One of these preventions are detention ponds, which primary function is the equilibration of water, but have also proven to have the capacity to remove many particle-bound pollutants by sedimentation. What's not as known is to what extent. The investigated detention ponds were compared to see to what extent they had accumulated particle-bound elements such as heavy metals, phosphorus and sulphur. This because it is essential to clarify whether they embody ecotoxicological hotspots and if when dredged will have sediment classified as hazardous waste. What was found in this study was that there was no significant difference in accumulation of pollutants or sediment depending on inlet or outlet, a difference between these could still be seen though by looking at the figures. The sediment of some of the detention ponds also had levels of the investigated elements higher than existing guideline values recommend for living organisms in the sediment and could also be classified as hazardous waste when emptied. More investigations need to be done, for example about how hydrology, plant uptake and design affect the sedimentation of pollutants to know for sure how the accumulation of pollutants in detention ponds work.

Increasing population across the globe paved the way for rapid growth in industrialization. Pharmaceuticals, automotive, textiles, agriculture, electronics, electrical and many other industries discharge different types of heavy metals, dyes and organic contaminants into ground water. These discharges are released into lakes and rivers without prior treatment causing huge environmental impact to the environment. Among different remediation techniques, adsorption was considered the most promising method because of its low-cost and high efficiency. Biomass is considered as the most practical and renewable source for production of bio products and biofuels. Biomass is also used for carbon sequestration and as an essential element to produce hydrochar and biochar which are considered as the 21st century black gold. Hydrochar and biochar can be used as an excellent low-cost adsorbent for the removal of heavy metals, dyes and organic contaminants from water. This dissertation work focuses on, firstly, development of novel oxone treated hydrochar as an adsorbent for the efficient removal of Pb(II) and Methylene Blue (MB) from aqueous solutions. Secondly, preparing novel ozone oxidized hydrochar treated with polyethyleneimine for removal of Remzol Brilliant Blue (RBB) and Remzol Reactive Black (RRB) dyes from aqueous solutions. Thirdly, producing high-performance CO2 activated biochar as an adsorbent for efficient removal of Aniline from aqueous solution. All prepared hydrochar and biochar adsorbents were characterized by SEM, TGA, FTIR, Elemental analysis, conductometric titration, and N2 adsorption-desorption isothermal analyses (BET and BJH). The adsorption capacities were determined by Atomic absorption spectrometry (AAS) and Ultraviolet–visible spectroscopy (UV-VIS) respectively. The adsorption capacity of each prepared biochar or hydrochar was determined and both kinetic and isothermal studies were performed. The optimal preparation conditions and adsorption parameters were determined for each adsorbent.

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