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 tShell powder (SP) with chitosan (CS) immobilized was applied as a composite biosorbent (CS-SP) for adsorptive removal of Congo red from aqueous solution. The materials were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. Dye adsorption onto SP and CS-SP was investigated under varied conditions such as chitosan content, initial dye concentration, pH, salt concentration, and temperature. The optimum CS content was determined as 15 wt%, under which CS-SP displayed a fine coating structure and a greater adsorption capacity of 258.53 mg/g compared with 36.50 mg/g for SP at 30°C. The composite adsorbent maintained its performance in high-salinity, acidic or alkaline environment, and exhibited excellent reusability throughout five-recycle regeneration. The dynamic data conformed to pseudo-second-order and Elovich models while the equilibrium isotherms followed Langmuir and Temkin models, which revealed that chemisorption was involved in the adsorption mechanism. Besides, the maximum monolayer adsorption capacity for 283.29, 322.58 mg/g at 30°C, 40°C, and 50°C, respectively, and adsorption on CS-SP was verified to be endothermic and spontaneous from thermodynamic study. The results indicated that the prepared CS-SP biosorbent is quite promising for dye wastewater treatment.