The Use of Aminated Wheat Straw for Reactive Black 5 Dye Removal from Aqueous Solutions as a Potential Method of Biomass Valorization

Abstract

Straw is a by-product from cereal cultivation. Using straw surplus as a biofuel is a popular means of its management. However, before being used for fuel purposes, straw can be successfully used as a sorbent. The present study investigated the sorption properties of wheat straw (Triticum aestivum L.) modified with ammonia water and epichlorohydrin against the reactive dye Reactive Black 5 (RB5). The tested sorbents were characterized based on FTIR, elemental analysis (C/N content), and pHPZC. The scope of the research included, among others, research on the effect of pH (pH 2–11) on the RB5 sorption efficiency, research on sorption kinetics, and determination of the maximum sorption capacity of the tested sorbents. The sorption efficiency of RB5 on the tested sorbents was the highest at pH 2–3. The experimental data from the research on the sorption kinetics of RB5 were best described by a pseudo-second-order model. The introduction of primary amine groups to the structure of sorbents significantly increased their sorption capacity towards RB5. The obtained sorption capacity of the aminated straw and the aminated straw pre-activated with epichlorohydrin was 24.12 mg RB5/g and 91.04 mg RB5/g, respectively, and it was higher by 44.3% and 444.5% compared to the unmodified straw.

Aminated Rapeseed Husks (Brassica napus) as an Effective Sorbent for Removing Anionic Dyes from Aqueous Solutions

“…Sorption equilibrium times similar to those for RH, RH-A, RH-E were also obtained in the studies on the sorption of RB5 on goldenrod biomass (150 min) [ 39 ], wheat straw (195 min) [ 40 ] and sunflower biomass (210 min) [ 41 ]. In turn, equilibrium times similar to that of RH-EA were recorded in the studies addressing the removal of RB5 on activated carbon from Carob tree (120 min) [ 42 ] as well as biochar from gasification of wood waste [ 43 ].…”

“…The sorption effectiveness of rapeseed husks modified with epichlorohydrin and then aminated with ammonia (RH-EA) is much greater than that of non-modified lignocellulosic biosorbents, such as seed husks, plant stalks or sawdust ( Table 5 ). The process of biomass amination that had earlier been pre-activated with epichlorohydrin effectively increases the sorption capacity of other lignocellulosic materials, like sunflower seeds and buckwheat sed husks, wheat straw or Canadian goldenrod biomass, as described in our previous works [ 19 , 34 , 39 , 40 ].…”

The Effect of Modifying Canadian Goldenrod (Solidago canadensis) Biomass with Ammonia and Epichlorohydrin on the Sorption Efficiency of Anionic Dyes from Water Solutions

“…The shorter equilibrium times of dye sorption onto GB-EA compared with GB, GB-A, and GB-E stemmed from a high concentration of -NH 2 groups on the sorbent’s surface. The amine functional groups of GB-EA, protonated at pH 3, were responsible for a strong positive charge on the sorbent’s surface, which intensified and accelerated the dyes’ binding from the solution [ 20 , 21 , 23 ]. No similar effect was observed in the case of GB-A ( Figure 4 ), due to a substantially lower content of primary amine functional groups.…”

“…The second phase probably began when most of the active sites of the sorbent’s surface had been saturated. This phase was less intensive but substantially longer than the first one, and consisted of the saturation of the last free sorption centers on sorbent’s surface [ 20 ]. In addition, strong competition was observed in this phase between dye molecules for the last available sorption centers.…”

“…Appropriate chemical modification of plant biomass can significantly increase its sorption capacity. This is the case with amination, which consists of incorporating primary amino groups [ 20 , 21 ] into the sorbent’s structure. As a result, the modified material, and likewise chitosan, gains an alkaline nature and a much higher capacity for anionic dye sorption [ 22 ].…”