Activated carbon was prepared from corn cob agricultural waste with different impregnation ratios and pyrolysis times. The optimal adsorbent prepared using at 4:1 ZnCl2:corn cob char ratio at a temperature of 800 °C for 180 min provided the maximum Brunauer-Emmett-Teller (BET) surface area, total pore volume and average pore width, with values of 912.47 m2/g, 0.52 cm3/g and 22.61 Å, respectively. ZnCl2 was effective in creating well-developed pores on the surface of the activated carbon. The removal efficiency and adsorption capacity of the colour and the chemical oxygen demand (COD) of the biologically pre-treated leachate were examined utilizing the best corn cob activated carbon (CCAC) with varying CCAC dosages, contact times and initial pH values. The greatest colour and COD removal effectiveness were 88.6±0.2% and 83.7±0.4%, respectively, at the optimum CCAC dosage of 12 g for 40 min with an initial pH value of 10. In addition, maximum adsorption capacities were achieved for colour and COD of 10.3±0.02 mg/g and 12.6±0.05 mg/g, respectively, under the same conditions. The kinetics of colour and COD adsorption fitted very well with pseudo-second-order kinetic model. The CCAC performs well as an adsorbent for removing colour and COD in biologically pre-treated leachate.

Increasing the pollution rate of water sources is one of the most severe issues that the world faces. This issue has stimulated researchers to investigate different treatment methods such as adsorption, chemical precipitation, membrane filtration, flocculation, ion exchange, flotation, and electrochemical methods. Among them, adsorption has gained broad interest due to its ease of operation, low cost, and high efficiency. The critical factor of the successful adsorption treatment process is finding attractive adsorbents with attractive criteria such as low cost and high adsorption capacity. In the last few decades, nanotechnology has attracted much attention, and numerous nanomaterials have been synthesized for water and wastewater treatment. This work provides a quick overview of nanomaterials, which have been investigated for water remediation as adsorbent and photocatalyst. This work reviewed more than 100 articles to provide a critical review that would determine the limitation of using nanomaterials in water treatment at the commercial scale.

The effect of ceramic filter composition on improving the quality of produced water by reducing total dissolved solids (TDS), barium, and phenol for reverse osmosis (RO) treatment was investigated in the present work. The ceramic filters were fabricated using a residue catalytic cracking (RCC) unit spent catalyst with and without activation, clay, and Dioscorea hispida starch (DHS), at various compositions.  The result showed that the optimum removal of TDS, barium, and phenol in produced water was achieved at a flow rate of sample 7 L/min and an operating time of 90 min. Ceramic filter with the composition of 60% spent catalyst without activation: 37.5% clay: 2.5% DHS reduced 34.84% TDS, 27.97% barium, and 71.11% phenol. While, the ceramic filter with a composition of 37.5% activated spent catalyst: 60% clay: 2.5% DHS was removed 51.44% TDS, 27.93% barium, and 85.29% phenol from produced water. The next steps of treatment of filtrates of the ceramic filter using reverse osmosis (RO) membrane showed that the permeate met the Indonesian standard for oil and gas wastewater. In addition, adsorption of TDS, barium, and phenol from produced water was dominated by clay composition in the ceramic filter.

The production rate of industrial and agricultural waste is increasing due to population growth. Soil is the most important receiver of industrial and agricultural waste. Contaminants such as heavy metals in various waste after reception by the soil, immediately become part of the cycle that has different impacts on the environment. Geopolymer, as a chemical stabilizer has the potential to stabilize heavy metals in the soil. In this research, several geopolymers for the stabilization of heavy metals in soil were synthesized. Silicon dioxide (SiO2) and aluminosilicate (Al2SiO4) must be used to produce the geopolymers. Rice husk ash was used as the SiO2 source. Also, Iranian zeolite and sepiolite, and red clay soil were utilized as the source of Al2SiO4. The synthesized geopolymers were investigated for the adsorption of nickel and cadmium. Also, batch and column studies of using geopolymers for the chemical stabilization of heavy metals in soil were conducted. The results revealed a high adsorption capacity of the geopolymers. The zeolite, sepiolite, and red clay geopolymer-soil samples adsorbed 100% of the heavy metals (i.e., Ni and Cd) at a concentration of 100 ppm. The zeolite geopolymer adsorbent adsorbed 57% and 96% of Ni and Cd at a concentration of 1000 ppm, respectively. In general, it was concluded that the use of geopolymer compounds in soils with high heavy metal adsorption capacity could be an efficient approach to prevent groundwater resource pollution.

Arsenic (As) contamination in the groundwater of Bangladesh is one of the major public health concerns. It has become a challenge to remove As from groundwater and a great deal of efforts employed in this regards with limited success. Cerium oxide is one of the important medias of arsenic removal techniques. Nine units of cerium-based arsenic technology were tested with seven different well waters in five hydro-geological areas in Bangladesh. Interestingly, the same technology showed variable results in terms of As removal performance from well water. Therefore, this study aimed to investigate the reasons behind the variant performance of the As removal technology. The studied wells were contaminated with a range of 283 to 873 μg/L of arsenic, 0.35 to 10.4 mg/L of iron, 0.29 to 6.83 mg/L of phosphate, 32.5 to 49.5 mg/L of silicate, 0.08 to 0.25 mg/L of sulfate and pH range was 7.11 to 7.65. The cerium-based As removal technology consistently produced As safe water from three wells containing more than 80% As (III) of total arsenic (As) and >3 mg/L of iron and reduced As concentration to below 50 μg/L consistently but failed at other four wells containing less than 75% As (III) of tAs and

Arsenic is a highly toxic element for human beings, which is generally found in groundwater. Dissolved Arsenic in water can be seen as As+3 and As+5 states. The adsorption process is one of the available methods to remove Arsenic from aqueous solutions. Thus, this papers aims at removing Arsenic (III) from aqueous solutions through adsorption on iron oxide granules. The relation among four independent variables, namely the initial concentration of Arsenic (III), pH, adsorbent dose, and contact time have been investigated through Response Surface Methodology. Design-Expert software and Central Composite Design method have been used to design and analyze the experiments and results. Also, SEM and FTIR analysis have been conducted to characterize the absorbent morphology. The optimum initial concentration of Arsenic (III), pH, contact time, and adsorbent dosage are 30ppm, 5, 49.99min, and 8g/l, respectively. Under these optimum conditions, the Arsenic (III) removal efficiency is 67%. The predicted 2FI model shows the highest Arsenic removal coefficient (R2=0.887).

The present study was carried out to investigate the adsorption and leaching behavior of Cu2+, Zn2+ and Pb2+ by sediments collected from the western banks of three different sectors along River Nile at Aswan governorate, Egypt. The feasibility of sediments for the removal of Cu2+, Zn2+ and Pb2+ from aqueous solutions was tested under the effect of three conditions (pH, initial metal concentration and contact time). By increasing pH, the adsorption of Cu2+ and Pb2+ by sediments decreased while that of Zn2+ increased. The optimum pH values for Cu2+, Zn2+ and Pb2+ removal were determined as 5, 8.5 and 5, respectively. The adsorption capacities of sediments for metal ions were in the order of Pb2+ > Cu2+ > Zn2+. The maximum uptake for Cu2+, Zn2+ and Pb2+ by sediments occurred at contact times of 48 h, 24 h and 72 h, respectively. Adsorption data were fitted well by Freundlich, Dubinin–Radushkevich and Temkin isotherms. The experimental results obtained were analyzed using two adsorption kinetic models, pseudo-first-order and pseudo-second-order, in which pseudo-second-order equation described the data more than pseudo-first-order one. The average leaching percentages of Cu2+, Zn2+ and Pb2+ from sediments were 0.77%, 2.72% and 0.38%, respectively, with respect to pH, 0.83%, 2.49% and 0.38%, respectively , with respect to temperature, and also 0.79%, 2.34% and 0.38%, respectively with respect to contact time. The leaching percentages of metal ions from sediments were in the order of Zn2+ > Cu2+ > Pb2+.

Management of solid wastes is considered as an economic and environmental issue in the building stone industry. The current study uses raw and calcined calcareous sludge, generated in the stone cutting factories, in order to remove sulfur dioxide. Sludge characterization has been performed, using X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) analyses. The removal experiments of sulfur dioxide have conducted under different humid contents and adsorbent doses. The results showed that the higher the adsorbent dosage and humidity content, the greater the SO2 adsorption.. The calcination process at temperatures of 400, 500, 600, and 700℃ revealed that with rising calcination temperature and humidity content, the adsorbent capability is enhanced considerably. This method could be developed for the management of stone sludge produced from the stone cutting industry through its conversion into an effective and low-cost adsorbent for desulfurization process.

The magnetic derivative of Activated Carbon (AC) is a promising new technique to isolate and recover consumed adsorbent. In this light, the current research seeks to summarise the magnetisation rout of AC and its applications, while identifying both benefits and drawbacks of different synthetic routs. Several methods, such as chemical co-precipitation, hydrothermal, impregnation, ball milling, and one-step synthetic routs, have been studied by previous researchers. Among these methods, chemical co-precipitation is simple, extensively adapted for Magnetic Activated Carbon (MAC) syntheses. In general, the magnetic derivatives of AC show a reduction in the surface area and pore volume, due to introduction of magnetic nanoparticles. Magnetisation enhances contaminants' adsorption, despite the reduction in surface area. It allows elimination of contaminants, barely treated by pristine AC due to the introduction of magnetic materials. Developments in synthetic procedures could overcome the destructive influence of acidity on MAC, providing a shield against it. MAC has been used in several applications, including organic and inorganic contaminant removal. Medically, MAC is used to lead drugs to a specific organ and, thus, reduce damages to non-affected organs. It can be said that the preparation method did not obstruct MAC application for specific contaminant adsorption. MAC regeneration has been reported for several sorption cycles, making the process sustainable and cost-effective. Future work could further develop the synthetic route and enhance the characteristics of the produced composite. It also may consider the influence of iron on the treated water, depending on its proposed usage.

For the first time, the present study removes ions of mercury, in the form of Hg (I) and Hg (II) ions, from aqueous solutions by adsorbing them onto titanium dioxide nanoparticles. The effects of various parameters, such as solution's initial pH, temperature, sorbent dosage, initial mercury concentration, and contact time have been examined on the adsorption process. The experimental results have been compared with Langmuir, Freundlich, and Temkin adsorption isotherms. The maximum adsorption, obtained for Hg (I) and Hg (II) ions, have been 97.5% and 98.6%, respectively. Also, it has been shown that the Langmuir isotherm has better fitting with the equilibrium data than the Freundlich and Temkin isotherms. Thermodynamic parameters of the adsorption, such as and  have been calculated, the negative values of which show that the mercury ions adsorption is an exothermic process and that randomness is decreased, respectively. The study of adsorption kinetics shows that the adsorption of Hg (I) and (II) ions with TiO2 nanoparticles is pseudo-second order.