Abstract
In this paper, we consider the possibility of using inexpensive and effective sorption materials based on plant raw materials, such as fruit rind, vegetable waste, fallen leaves, and the use of phytosorbents for the purification of sewage containing heavy metals and petroleum products. The use of vegetable waste for the manufacture of sorbents is a priority for solving environmental problems. It is suggested to use residual biomass as a sorption material, which is formed after extraction of lipids from C. sorokiniana microalgae and duckweed Lemna minor. To increase the sorption capacity, it was proposed to thermally modify the residual biomass. The optimum heat treatment conditions were 450 °C for 20 minutes with limited access to oxygen. The obtained biomass allows one to extract ions of heavy metals with efficiency of 91-93% for ions of lead, cadmium, zinc and copper. To increase the sorption capacity (A, mg/g) of the residual biomass, heat treated waste from the agro-industrial complex and chitosan were proposed as additives. The addition of chitosan makes it possible to obtain a sorption material in the form of granules, which is convenient to use. For the sorption materials obtained, microstructural studies were carried out, which allowed us to substantiate the sorption properties of the materials. The physical and mechanical properties of sorbents, such as abrasion, grindability, allow us to offer new materials for use on an industrial scale. In the article, a technological scheme for obtaining sorption materials from residual biomass is given.
Highlights
Microalgae are intensively used in various branches of the national economy, for example as additives for livestock, materials for biologically active additives, phytosorbents for wastewater purification and so on [1,2,3,4,5]
For obtaining granules based on chitosan, thermally-treated residual biomass (TTB) and thermally-treated wastes from the agro-industrial complex (TTWA) we prepared mixture of the following composition: 40 g of chitosan is added to 960 g of 3 % acetic acid
To determine optimum conditions of thermal treatment of the residual biomass we carried out thermogravimetric analysis (Figure 1), which showed that the treatment should be performed within temperature range from 200 to 500 °С
Summary
Microalgae are intensively used in various branches of the national economy, for example as additives for livestock, materials for biologically active additives, phytosorbents for wastewater purification and so on [1,2,3,4,5]. It is known from literature that microalgae biomass contains cellulose as the major component (23.5%), starch, hemicelluloses, chitin- and pectine-like substances. Containing of cellulose, hemicellulose and chitin substances determine sorption properties of biomass, so usage of algae for water purification is advantageous [6]. It is known that C. sorokiniana, C. vulgaris and S. obliquus microalgae are used as sorbents for purification of wastewaters from pharmaceutical production. The most efficient removal of paracetamol was obtained using the C. sorokiniana strain [7]. The paper [8] presents consideration of C. sorokiniana microalga as a biosorbent for heavy metals. C. sorokiniana showed the highest efficiency of lead ions removal from wastewater in comparison with other metals. Due to large ion radius it is the easiest to embed into the cell wall
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