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Magnetic modified graphene oxide was synthesized as a new modified magnetic nano-composite (MMNC) by a simple sonochemical–hydrothermal method. The sonochemical reaction was employed to exfoliate, functionalize and decorate neomycin on graphene oxide sheets. Nickel ferromagnetic particles were synthesized by hydrothermal co-precipitation method and decorated on neomycin-modified graphene oxide. The morphology and chemical structure of MMNC were characterized by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction spectroscopy. The adsorption capability of MMNC for removal of phenolic compounds was assessed through adsorption of 4-nitrophenol (4-NP) from aqueous solution. The three-factor Box–Behnken design coupled with response surface method was applied to evaluate and optimize the important variables which affect the adsorption process. A significant quadratic model (p-value <0.05, R2(adj) = 0.9593) was derived using analysis of variance. The maximum adsorption capacity of 125.4 mg 4-NP/g MMNC at pH 6 was obtained, which was comparable in some cases and higher than most adsorbents reported in the literature. The presence of neomycin on graphene oxide sheets improved the maximum adsorption capacity of the nano-sorbent up to 28% (from 98.7 to 125.4 mg 4-NP/g adsorbent). The adsorption isotherms fitted well with the Langmuir model (Langmuir constant b = 0.064 l/mg, R2 = 0.9989) and the kinetic study showed that the nitrophenol uptake process followed the pseudo-second-order rate expression (R2 ≥ 0.9960, pseudo-second-order constant K2 ≥ 1.7 × 10−3).

Background Risk assessment of gas pipelines is very important because of various hazards and economic losses. Using fuzzy logic increases the reliability and accuracy of the results. The purpose of this study is to evaluate the fuzzy risk of fire, explosion and release of toxic gas in the pipeline using fuzzy analytical hierarchy process. Methodology Extraction of all hazards from HAZOP and HAZID was carried out. Fuzzy risk assessment was performed using MATLAB software. Using fuzzy hierarchy process analysis, the weight of each basic risk item (BRI) was summed up in a framework, and the fuzzy risk level was determined with a five-state criterion including highly desirable, favorable, moderate, undesirable and highly undesirable. Results The final risk score was equal to 0.1492, which according to the five-state criterion the risk level is in the favorable area. The highest risk score was related to hot work with open flame item with a risk score of 0.2485. Conclusions The final risk score of fire, explosion and release of toxic gas in Siri–Assaluyeh gas pipeline is in the optimal area. Fuzzy risk assessment, compare to conventional risk matrices, provides more data to safety managers about the hazards and their rankings. Accordingly, the results are expected to be applicable to the safety managers while making decisions related to the risk management of gas pipelines.

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