Two novel adsorbents derived from shrimp shell were prepared and their adsorption performances on Congo red were investigated. The results suggested that treated shrimp shell powder exhibited a higher adsorption capacity than raw shrimp shell powder. The factors of initial concentration, solution pH, adsorption time, and temperature were investigated. The maximum adsorption capacity of treated shrimp shell powder calculated according to the Langmuir isotherm model was 288.2 mg/g, which is much higher than that of chitin. The adsorption behavior could be fitted well by the pseudo-second-order kinetic model. Intra-particle diffusion model was also used to study the adsorption process. The thermodynamic parameters indicated the spontaneous and endothermic nature of the adsorption. Shrimp shell powder exhibited enough advantages such as large adsorption capacity, low cost, simple processing methods and high specific gravity compared with chitin or chitosan. This work confirmed that the shrimp shell biosorbent had a potential to be applied in dye wastewater treatment area.

To explore the application of shell powder (SP) in rubber, a dye-loaded SP (DSP) bio-filler based on SP and Congo red was incorporated into natural rubber (NR). The adsorption experiments demonstrated that the maximum monolayer adsorption capacity of Congo red onto SP was 69.3 mg/g. The effect of aluminate coupling agent and DSP was investigated by evaluating the cure characteristics, mechanical, thermal, and coloring properties of NR/DSP composites. It was suggested that the optimum amount of aluminate coupling agent was 2 wt %, and the best tensile strength (24.80 MPa) of vulcanizates was achieved at the DSP content of 20 phr, while other mechanical properties such as tear strength kept increasing with the addition of DSP. Furthermore, the improved thermal stability and uniform color distribution of the NR composites was obtained. The results indicate that DSP is promising to become a low-cost filler and pigment for rubber materials.

a b s t r a c tChitin adsorbents with different degrees of deacetylation (DDA) were prepared from crab shells waste and applied in adsorptive removal of dye Congo Red (CR). The adsorbents were characterized by thermal gravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffraction, and elemental analysis. The effects of solid-liquid ratio, initial dye concentration, contact time, temperature, pH value, salt concentration, and DDA on adsorption were studied. It was indicated from orthogonal experiments that the removal of CR reached 99.28% under the optimum condition (DDA = 17.85%, pH = 5.40, and time = 20 h) at 300 K. The equilibrium data were plotted by Langmuir and Freundlich isotherms and described better with Langmuir model (Q m = 366.3 mg/g, 300 K) as the temperature increased and the adsorption kinetics was well fitted by pseudo-second-order equation. It was verified from the thermodynamic parameters (ΔG, ΔH, and ΔS) that the adsorption was spontaneous, exothermic and entropy decreasing. Functional groups including amino, acetyl amino, O-glycosides, and -O-on the pyranose ring of chitin were involved in adsorption as active sites through van der Waals force and hydrogen-bonding with the adsorbate. Moreover, CR adsorption on chitin with different DDA further revealed that the crystallinity of chitin played a more important role than amino group content.