Sorbents obtained from cellulose-containing waste for water

Environmental pollution by industrial emissions is currently an acute environmental problem. A significant part of wastewater of various origins enters the environment without treatment, which negatively affects human health, the environment and the economy.
Among the most dangerous carcinogenic toxicants contained in industrial waste water are heavy metals belonging to I and II hazard classes. They rank second in terms of toxicological effects on the human body, behind pesticides.
Heavy metals include lead (Pb), cadmium (Cd), arsenic (As), chromium (Cr), copper (Cu), nickel (Ni), cobalt (Co), zinc (Zn) and others. It is necessary to constantly monitor their concentration in water to detect and assess contamination.
To purify wastewater from water-soluble salts of heavy metals, chemical, physicochemical, biological and combined methods of water purification are applicable. However, these technologies are either often ineffective, produce secondary products, or are too expensive.
Among the physicochemical methods of detoxification of both gas and liquid media, adsorption stands out, as a universal process that allows to almost complete removing of toxic impurities. The successful solution of many practical problems is determined by the choice of sorbents with optimal physicochemical properties and cost for these purposes.
We developed a technology for obtaining carbon materials with a high surface area. This technology was used for many types of raw materials (used tires, hazelnut and walnut shells, nectarine kernel, sawdust, plastics, etc.).
The process is one-stage and does not require preliminary processing of raw materials. Carbon dioxide, water and various gases generated in the process are used as a reagents and energy sources. In this case, the reactor vessel (stainless steel) acts as a catalyst. Using this technology, carbon materials were obtained from recycled organic waste, which are cheap and efficient.
The physicochemical properties of the above materials were measured, namely, BET surfaces, areas and volumes of micropores (by capillary nitrogen condensation, on GEMINI VII), chemical composition (on a scanning electron microscope HITACHI TM 3030 Plus), ash content. The measurement results are published in several scientific articles. Studies have shown that these materials are characterized by a large specific surface area, porous structure, high adsorption capacity, and can be successfully used to extract various heavy metal ions from water separately. It was found that carbon materials obtained from hazelnut and walnut shells are characterized by the best adsorption properties with respect to ions of cobalt, lead, copper and iron. The maximum adsorption of ions such as cobalt, copper and iron, separately, is achieved in 30-45 minutes, and for lead ions, 5-10 minutes is enough.
The purpose of this work was to study the sorption properties of carbon material obtained from secondary raw materials (hazelnut and walnut shells) according to the technology we have developed; determination of its applicability in the purification of drinking and waste water, in which ions of several heavy metals are simultaneously present.
Studies of solutions of various concentrations of metal ions have shown that in the presence of all four ions, the maximum adsorption rate and the degree of extraction are achieved at a solution concentration of 0.0025 M Me+2 in 30 minutes.