Selective Removal of Sodium Ions from Aqueous Media Using Effective Adsorbents: Optimization by RSM and Genetic Algorithm

This study aimed to determine the best adsorbent among Moringa oleifera-derived activated carbon (AC), eggshell-derived CaO nanoparticles and CaO/Fe3O4 for sodium (Na+) removal from aqueous media. In the first step, the appropriate adsorbent for sodium adsorption was determined among the three adsorbents, which the results showed that the AC had the highest sorption efficiency. Then, response surface methodology (RSM) was used to evaluate the impact of different factors on the Na+ ion sorption efficiency using the AC. The highest removal efficiency was obtained to be 95.91% at optimum conditions such as pH of 11, contact time of 45 min, temperature of 25 °C, sodium ion concentration of 900 mg/L, and adsorbent dosage of 5 g/L. Also, the best conditions using the genetic algorithm was obtained at contact time of 94.97 min, adsorbent dosage of 3.52 g/L, Na+ ion concentration of 939.92 mg/L and pH value of 10.92. Moreover, the maximum sorption capacity using the Langmuir model was obtained to be 249.67 mg/g, which was a significant value. Besides, the equilibrium and kinetic studies indicated that the experimental data of sodium adsorption process were fitted well with the Langmuir isotherm model and the pseudo-second-order kinetic model, respectively. Furthermore, the thermodynamic study indicated that the sorption process was endothermic. Generally, among the three adsorbents used, activated carbon with a high removal efficiency and significant sorption capacity can be considered as a promising adsorbent for the removal of sodium from wastewater on an industrial scale.

Biosorbents for wastewater treatment

Biosorption is a promising technology for removing various pollutants from industrial wastewater, which consists in the use of secondary plant raw materials (e.g., agro-industrial waste) to solve environmental pollution problems. The purpose of this study is to evaluate the potential of nut shells as a biosorbent, to study the effect of alkaline modification of shells on their properties and to study the use of spent biosorbents as additives in cement. The influence of the fractional composition of the initial material on its sorption capacity and the influence of the modification of shells with alkaline solution on the properties of the obtained biosorbents are investigated. The yield of the final products was determined gravimetrically as the ratio of the mass of the product to the mass of the raw material. The sorption capacity was studied using model solutions. The concentration of sodium hydroxide solutions was determined by titration, and the cationic dye by spectrophotometric method. Methylene blue was used as a test dye. The studies have shown that the fractional composition of the material largely determines its sorption properties. Reducing the particle size of the nut shells leads to an increase in the sorption efficiency of methylene blue from 17.2% for the fraction with a size of 1.5-2.0 mm to 39.2% for the fraction with a size of 0.5-1.0 mm. The static exchange capacity increases by an average of 30 % for each subsequent fraction. To improve the sorption properties of the initial material, along with grinding, it is advisable to use chemical modification. The method of alkaline modification was used, which is accompanied by partial destruction of the aromatic component of raw materials and low molecular weight polysaccharides and by removal of extractives of different nature, which leads to the formation of a more porous structure. The maximum sorption efficiency of methylene blue (80 %) corresponds to the biosorbent obtained from nut shells (fractional composition 0.5-1.0 mm) by modifying with 5 % NaOH solution for 180 min at a temperature of 100 oC. Alkaline treatment significantly improves the adsorption capacity of the biosorbent to the cationic dye compared to the initial material. The sorption capacity of nut shells and biosorbent based on shells was studied as a function of pH of aqueous dye solution and duration of contact. It was found that pH of the aqueous solution had a significant effect on the sorption of the dye and the maximum value was reached at pH 6. This is due to the electrokinetic properties of the surface of lignocellulosic materials - the ability to change charge depending on pH (positive in acidic, negative in neutral and alkaline), due to the presence of different functional groups. The study of kinetics showed that the maximum rate of absorption of methylene blue corresponded to the first 30 minutes of contact. Sorption equilibrium is achieved within 240 minutes of contact. Sorption kinetics was also studied using pseudo-first and pseudo-second order models, as well as a diffusion model. The pseudo-second order kinetic model (R2 = 0.99) best describes the absorption kinetics of the cationic dye and suggests that the fixation of methylene blue on the surface of the biosorbent occurs due to various mechanisms. The problem of further use of spent sorption materials is no less important than the efficiency of sorbents in creating an effective integrated water treatment technology. Spent biosorbent was used as an additive to the composition of cement type I/500. The use of plant material in the amount of 5% will not lead to a significant deterioration of the physical and mechanical properties of cement. This indicates the prospects of such an approach in the utilization of spent sorbents. In further research, it is planned to investigate various modification options for plant materials for obtaining highly effective biosorbents of multipurpose function for the solution of environmental problems.

Recovery of niobium from wastes generated in titanium production by cation exchange sorbents

This article presents the technology of niobium recovery by processing of chloride residues generated during the chlorination of titanium slags. For waste processing, a two-stage leaching technology is proposed. Water is used at the first stage of leaching and hydrochloric acid 4.0 M is used at the second stage. For the purpose of sorption of niobium from the solution composition obtained during leaching, cation-exchange sorbents Purolite-C104 and KU-2-8 H were used. By the usage of Purolite-C104 ion exchange resin the sorption efficiency of niobium from a solution with a concentration of 2 g/l was about 71.0 % (0.071 g/g) in 3.5 hours, while for KU-2-8 H ion exchange resin, sorption efficiency was about 89.0 % (0.089 g/g).

Green Filtration of Total Solids from Various Water Sources Using Coconut Coir and Loofah

In this study, environmentally benign and readily available organic waste materials (coconut coir and loofah) were used as biofilters to remove total solids (TS) in water samples from various sources in Araromi Coastal Region of Ilaje Local Government, Nigeria. The TS levels observed in the river, pond, well, borehole, and seawater samples were 4,000, 1,610, 3,980, 2,600, and 34,800 mg/L, respectively. Generally, the organic filters reduced the TS in the water samples. Also, the sorption efficiency increased with the filter mass-to-water volume ratio. The overall performance of coconut coir was better than loofah, probably because the former has a more closely packed fibrous mesh. The optimum sorption efficiency of 60 g of the coconut coir filter for river, pond, well, borehole, and sea water was 50%, 78%, 80%, 92.3%, and 48.8%, while those for loofah were 42.5%, 56.3%, 70%, 84.6%, and 40.2%, respectively. This work showed that pretreated coconut coir is an efficient green filter for TS in water sources, especially boreholes, wells, and ponds.

Oil Sorption Performance of Sorbent Materials Examined Under Static and Dynamic Conditions

Oil spill cleanup and subsequent restoration of the environment is majorly a function of spill cleanup methods applied. Some of these methods, though efficient, are, however, very expensive and require more personnel for their application and relative deployment in the field. The study was aimed at examining the efficiency of a locally and readily available, eco-friendly and low cost agricultural waste (coconut husk coir) as sorbent materials for spilled engine oil cleanup under static and dynamic marine water conditions. The sorbent material was prepared and used in three forms: raw coconut husk coir (CHC), modified coconut husk coir (MCHC), and reused coconut husk coir (RCHC). Under static and dynamic marine water conditions, oil sorption batch equilibrium experiments were used to study the engine oil sorption capacity and efficiency of the sorbent. Effects of sorbent dosage and sorption times on the oil sorption and efficiency of CHC, MCHC, and RCHC were studied and determined. At a constant sorption time of 60 minutes and varying sorbent dosages of 2-8 /320 ml of engine oil-marine water concentration, MCHC exhibited the highest oil sorption efficiency of 61.18% and 44.33% for dynamic and static conditions, CHC had 55.61% and 38.50% for dynamic and static conditions, whereas RCHC had 41.66% and 26.04% for dynamic and static conditions, respectively. It is statistically deduced from the results that sorption times and sorbent dosages have significant effects on the sorption efficiency of experimental coir for spilled engine oil removal. Though there is a need for proper blending or modifications of the sorbent material to enhance its affinity to oil and hydrophobicity, there are enough potentials in the materials for mild marine water current spilled engine oil cleanup.

Preparation and Characterization of Novel Magnesium Composite/Walnut Shells-Derived Biochar for As and P Sorption from Aqueous Solutions

Elevated or unnatural levels of arsenic (As) and phosphorus (P) concentrations in soils and waterbodies from anthropogenic sources can present significant hazards for both natural ecosystems and human food production. Effective, environmentally friendly, and inexpensive materials, such as biochar, are needed to reduce mobility and bioavailability of As and P. While biochar features several physicochemical properties that make it an ideal contaminant sorbent, certain modifications such as mineral-impregnation can improve sorption efficiencies for targeted compounds. Here, we conducted sorption experiments to investigate and quantify the potential utility of magnesium (Mg) for improving biochar sorption efficiency of P and As. We synthesized a Mg-modified walnut shells-derived biochar and characterized its ability to remove As and P from aqueous solutions, thereby mitigating losses of valuable P when needed while, at the same time, immobilizing hazardous As in ecosystems. SEM-EDX, FTIR and elemental analysis showed morphological and functional changes of biochar and the formation of new Mg-based composites (MgO, MgOHCl) responsible for improved sorption potential capacity by 10 times for As and 20 times for P. Sorption efficiency was attributed to improved AEC, higher SSA, chemical forms of sorbates and new sorption site formations. Synthetized Mg-composite/walnut shell-derived biochar also removed >90% of P from real samples of wastewater, indicating its potential suitability for contaminated waterbody remediation.

Ecological Aspects of Clay Sorption Materials Usage in Leather and Fur Production Technologies

The work is devoted to solving the current problem of increasing the level of environmental safety of treatment industrial wastewater of leather production from chromium ions (III) through the use of natural and modified bentonite. The studies of natural and modified bentonite use in the adsorption of Cr3 + ions were conducted. The influence of the process duration on the sorption efficiency of chromium ions was studied. Studies were conducted to use spent bentonite in tanning and filling processes. The efficiency of modification of montmorillonite has been proved and the expediency of using mineral dispersion for qualitative formation of the structure and properties of the leather during tanning has been established.