Recent trends in Ni(II) sorption from aqueous solutions using natural materials

The use of materials of natural origin for the adsorption of heavy metal ions from aqueous solutions has gained attention in recent years among the scientific community. This is explained by the fact that nickel compounds, due to severe health consequences, are considered to be among the most dangerous to the environment. This article reviews the results of studies on the use of biosorbents for purification of aqueous solutions from nickel ions, and then attempts to classify them according to their origin. The characteristics of materials and their sorption capacity have been compared, and the removal mechanisms identified of which chemisorption and ion exchange are considered to be the most common. From the analyses, a major trend is the use of biomass; however, biosorbents from other groups also continue to attract the interest of researchers. Conducting laboratory studies can help select materials with high efficiency. The highest sorption capacity values for the materials in each group were: for waste products 56 mg Ni·g−1 (olive stone), for peat 61 mg Ni·g−1, for miscellaneous 225 mg Ni·g−1 (microbial flocculant GA1), for biomass 286 mg Ni·g−1 (Plantanus orientalis bark) and for composites/modified materials calcinated eggshells 769 mg Ni·g−1 (calcinated eggshells). However, for some materials the sorption phenomenon may be accompanied by precipitation in the presence of hydroxides, which significantly affects the sorption capacity achieved. There is a need to transfer these experiments to an industrial scale so as to verify their applicability. In such industrial scale applications, attention should be paid not only to the effectiveness of the material, but also to its availability, price, and ease of use, as well as the effect of the biosorbent in terms of changing the quality parameters of the aquatic environment.

Physicochemical and Sorptive Properties of a Phosphorylated Mercerized Cotton Fabric

A process of phosphorylation for a mercerized cotton kersey fabric was investigated. After wet oxidation, the phosphorus content in each sample was determined by spectrophotometric analysis. The range was 0.179 to 0.950 mmol g–1. A significant decrease in the tensile strength of samples resulted from an increase of phosphoric acid concentration in the phosphorylating solution. The mercerization has a positive impact on the process of phosphorylation, as the phosphorus content was found to be three times higher in the samples that underwent mercerization. The sorption properties of phosphorylated cotton fabric were studied using the Cu2+ sorption process as a reference. The value of the static exchange capacity for the phosphorylated fabric was determined to reach its maximum when the concentration of the H3PO4 in the phosphorylating solution was 1.40 M, and was found to be 1.48 ± 0.11 mmol g–1 with the phosphorus content equal to 0.898 ± 0.090 mmol g–1. The sorption of Cu2+ by a single phosphorus-containing group occurred for samples with phosphorus content not exceeding 0.80 mmol g–1. The preliminary studies of micro-quantities of 241Am, 233U, and 239Pu radionuclide sorption from aqueous solutions with phosphorylated textile demonstrated the high efficiency.

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.

The use of air-lift adsorber with a floating filling from a cross-linked chitosan hydrogels for Reactive Black 5 removal

This work substantially extends knowledge on the possibilities of treating colored industrial wastewater via sorption under flow conditions. The presented study aimed to determine the effectiveness of Reactive Black 5 (RB5) dye sorption from aqueous solutions under dynamic (flow) conditions in an unconventional air-lift type loop reactor with a filling made of hydrogel chitosan sorbents. The dye was removed from mono-component solutions (deionized water + RB5) and synthetic dyeing wastewater containing RB5 dye, NaCl (3 g/L), and an anti-creasing agent—UNICREASE JET (2 g/L). The sorbents tested in the study included: unmodified chitosan (CHs), chitosan ionically cross-linked with sodium citrate (CHs-CIT), and chitosan covalently cross-linked with epichlorohydrin (CHs-ECH). Each experimental series aimed to determine: the bed break-through time (CE = 0.1 C0), time of depletion of the sorbent’s sorption properties (CE = C0), and maximal sorption capacity of the sorbents (Qmax). The data obtained under dynamic conditions were described using Thomas, Yoon–Nelson, and Bohart–Adams models. The volume of the solution effectively treated in the air-lift reactor was significantly affected by chitosan sorbent type. At C0 = 50 mg RB5/L, the adsorber with the filling made of 1 g d.m. CHs allowed for the effective treatment of 4.6 L of synthetic wastewater (Qmax = 1504.7 mg/g), whereas CHs-ECH ensured 34.6 L of the treated solution (Qmax = 3212.9 mg/g).

Lead sorption from aqueous solutions by kaolinite: laboratory experiments

The lead has adverse effects in contamination the aquatic environment, for this reason, a laboratory simulation was conducted using kaolinite collected from the Ga’ara Formation at western Iraq to be considered as a natural sorbent material that can be addressed Pb2+ from the aqueous environments. The Energy-Dispersive X-ray Spectroscopy and atomic absorption spectroscopy clarifying very fine grains and pure phase with a very little quantity of quartz and has a number of active sites for adsorption. The sorption of kaolinite for the Pb2+ has been carefully tested by several designed laboratory experiments. Five lead solutions of different concentrations (25, 50, 75, 100 and 125 ppm) were tested under different values of pH (1.3-9). The best sorption has been recorded at pH 9, with an equilibrium reaction time 40 m and the solid-liquid ration 1.25 gm:50 ml. The sorption reaction is endothermic with two main mechanisms were identified, the rapid ion exchange which gets at the beginning of the reaction during the first 10 m, and ion exchange, which gets slow later due to form ionic complexes

Removal of methylene blue from aqueous solutions by adsorption on amorphous silicon dioxide from rice husks

This study shows the effect of conditions on methylene blue sorption from aqueous solutions using amorphous silicon dioxide obtained from rice husk by oxidative roasting with and without pre-treatment with 0.1 M HCl. Adsorption activity for methylene blue increases with increasing pH, reaching its maximum above the point of zero charge. Thermodynamic parameter values (ΔG298 > 0, ΔH < 0, ΔS > 0) indicate that methylene blue adsorption is exothermic and occurs with an increase in molecular mobility in the adsorption layer. The process is described by the Freundlich and Dubinin-Astakhov equations, which indicates that it is determined by both electrostatic interaction with active centers on the surface and the volumetric filling of micropores.