Summary: A series of hydrogels as heavy metals adsorbent were prepared from chitosan and acrylamide by gamma irradiation at room temperature. Chitosan solutions with different concentration (1%, 2%, 3%) (w/v) have been mixed with 7.5% (w/v) of acrylamide and irradiated at doses of 10-40 kGy. The properties of the prepared hydrogel of chitosan-co-poly(acrylamide) (Chi-co-PAAm) were evaluated in terms of the gel fraction and degree of swelling. It was found that the incorporation only 3% (w/v) chitosan with 7.5% (w/v) acrylamide can produces an elastic hydrogel when irradiated with gamma rays up to 15 kGy. Batch adsorption experiments were carried out to study heavy metals ions removal from its aqueous solutions. The different parameters effecting on the adsorption capacity such as contact time, pH of the solution, hydrogel dose, initial metal ion concentration, and competitive ions were investigated. The results indicated that the ions uptake performance of the hydrogel significantly changed with all the parameter tested. However, Chi-co-PAAm hydrogel demonstrated a great uptake ability for heavy metal ions. The order of heavy metal ions uptake on Chi-co-PAAm hydrogel was Zn 2þ > Cr 6þ > Pb 2þ > Cu 2þ > Co 2þ > Ni 2þ . The Freundlich and Langmuir adsorption isotherms models were applied to describe the isotherms and isotherm constants the adsorption data obtained in this study.

In this study, we synthesized the adsorbent based zeolite as an adsorbent for toxic metal removal. The modified zeolite adsorbent has been successfully synthesized using polymerization radiation technique by gamma rays. The monomer of acrylamide was applied to be grafted onto zeolite. The irradiation doses used in this study were 10–75 kGy and we obtained the optimum dose for synthesizing the zeolite-g-polyacrylamide by using the simultaneous irradiation technique was 25 kGy, with 99.88% and 48.01% for the gel fraction and degree of grafting, respectively. The zeolite-g-polyacrylamide were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Scanning Electron Microscope (SEM).

The improvement of Bangka’s white pepper quality in term of microbial contamination and physicochemical parameters has been done using gamma irradiation. Pepper samples were irradiated using gamma rays with dose of 2 to 10 kGy, and 0 kGy as unirradiated (control). The Harwell dosimeter was used to determine the absorbed dose. To evaluate the storage effect on the Bangka’s white pepper quality, the optimum irradiation dose of 8 kGy was used and peppers were then kept at room temperature (27°C) for 3, 6, 9 and 12 months. The results showed that unirradiated sample was contaminated by bacteria and mold, both of them with concentration of 103 up to 104, while there was no contamination of yeast, E. coli and Salmonella. The physicochemical properties such as light berries, dark-colored berries, moisture, piperine and essential oil contents were 1.7, 0.7, 11, 5.5 and 2.8 (w/w), respectively. Gamma irradiation with dose of 2, 4, 6, 8 and 10 kGy reduced the number of bacteria to 3.5x101, 2.5x101, less than 10, less than 10 and 1.5x101 cfu/g, respectively. While for mold, irradiation from 2 up to 10 kGy reduce the number of molds to become less than 10 cfu/g. From the dose evaluation, irradiation dose of 8 kGy was selected to evaluate the effect of storage time. It was found that storage time up to 12 months, unirradiated sample still showed contamination of bacteria from 103 up to 104 cfu/g, while the irradiated pepper showed the contamination less than 10 cfu/g. The effect of storage time on physicochemical properties showed that there is no significant change for both unirradiated and irradiated pepper even after kept for 12 months. Piperine and essential oil contents of unirradiated pepper were 5.45 and 2.4%, respectively. Irradiated pepper showed slightly higher piperine content compared to un-irradiated. It can be concluded that gamma irradiation with a dose of 8 kGy is effective to improve the quality of Bangka’s white pepper while maintaining its bioactive substances (piperine and essential oil) and other physicochemical properties as well.

Chitosan has been used as antimicrobial, anti‐fungal, anti‐virus, antioxidant, and anti‐cancer agent. As a new biomaterial, chitosan will be required to undergo certain toxicity tests for biocompatibility and safety assessment; one of the requirements is acute toxicity. In this study, nonirradiated and irradiated chitosan is used. The MW of chitosan is analyzed using GPC. The degree of deacetylation (DD) is measured by FTIR. OECD Guideline for Testing of Chemicals No 423 is used for evaluation of acute oral toxicity tests of nonirradiated and irradiated chitosan using mice with body weight (BW) ranging from 20 to 30 g. During 14 days after the dosing of chitosan, there are daily observations of toxic symptoms, death of test animals, changes in weight gain, and manifestations of toxic effects of individual animals. The results show that nonirradiated and irradiated chitosan with 75 kGy have an average MW of 276.0 and 90.0 kDa, respectively. Chitosan has a DD of 92%, which is increased by 4% at 75 kGy irradiation dose. Administration of nonirradiated and irradiated chitosan with a concentration of 300 mg/kg BW and continuous following with 2000 mg/kg BW show no toxic symptoms or death of mice test animals, LD50 > 5000 mg/kg. It is concluded that nonirradiated and irradiated chitosan with 75 kGy are categorized as practically nontoxic with LD50 > 5000 mg/kg. The dose up to a test limit of 5000 mg/kg BW is estimated to be equivalent to the dose of 38.79 mg (≈ 38.79 g) in humans (70 kg).

Zeolite‐g‐polyacrylamide is prepared by using the radiation induced grafting technique. Clinoptilotite, a natural zeolite, is used as the base matrix. In order to increase the degree of grating of polyacrylamide into the zeolite, its surface is modified with silane compound before the grafting reaction and applied a poor solvent method in the grafting reaction, i.e., a mixture of toluene and H2O. The irradiation doses are varied from 10 to 50 kGy. The grafting parameters are 40% w/w acrylamide, temperature 60 °C and 3 h grafting time. The highest degree of grafting is 93% at an irradiation dose of 25 kGy. The zeolite‐g‐polyacrylamide is then characterized with FTIR spectroscopy and SEM observation. Batch experiments are also carried out to investigate the adsorption capacity for ion Cr3+, Pb2+, and Zn2+. The maximum adsorption capacities of zeolite‐g‐polyacrylamide are 544, 345, and 1046 mg g−1 for ion Cr3+, Pb2+, and Zn2+, respectively. The equilibrium data are also tested with Langmuir and Freundlich isotherm to find the best suitable adsorption isotherm system.