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A B S T R A C TThe present study addresses the application of raw and modified carbon nanotubes (CNTs) and activated carbon (AC) for the removal of hexavalent chromium (Cr(VI)) from aqueous solution. Surfaces of both the adsorbents were modified by acid treatment. Nitric acid was used to remove impurities and to introduce carboxylic functional groups on the surfaces of CNTs and AC. Raw and modified adsorbents (CNTs and AC) were characterized by scanning electron microscopy, Brunauer-Emmett-Teller surface area analysis, and thermogravimetric analysis. The influence of adsorbent dosage, contact time, agitation speed, and solution pH were evaluated on the Cr(VI) removal efficiency using batch adsorption experiments. The optimum pH for maximum adsorption of Cr(VI) was found to be 3 and 4 for AC and CNTs, respectively. Modified and raw AC were able to remove 99 and 92% of Cr(VI) ions, respectively, at 75 mg adsorbent dosage, agitation speed of 200 rpm, initial Cr(VI) concentration of 1 mg/L, contact time of 4 h, and solution pH 3, while the removal of Cr(VI) ions recorded maximum values of 87 and 80% for modified and raw CNTs under same treatment conditions. However, acid modification of CNTs was found to have no major effect on the percentage removal of Cr(VI) ions at low adsorbent dosage. Adsorption capacities of both the adsorbents were determined using batch adsorption experiments and experimental data were described by Langmuir and Freundlich adsorption isotherm models. However, Langmuir isotherm model was able to best describe the adsorption of Cr(VI) ions on raw and modified forms of CNTs and AC. Maximum adsorption capacity (q e ) was found to be 2.024 and 1.805 mg/g for raw and modified AC, while 1.021 and 0.964 mg/g for raw and modified CNTs.

We compute the Hilbert series of general weighted flag varieties and discuss a computer‐aided method to determine their defining equations. We apply our results to weighted flag varieties coming from the Lie groups of type G2 and GL(6), to construct some families of polarized projective varieties in codimensions 8 and 6, respectively.

This is a first introduction to unprojection methods, and more specifically to Tom and Jerry unprojections. These two harmless tricks deserve to be better known, since they answer many practical questions about constructing codimension 4 Gorenstein subschemes. In particular, we discuss here the two smoothing components of the anticanonical cone over P(1, 2, 3).Section 2 treats the "6 × 6 extrasymmetric format", that describes the Segre embedding of P 2 ×P 2 and some of its degenerations. One can view this as just algebraic manipulations, or as a typical case of Tom unprojection. In a similar vein, Section 3 treats the "Double Jerry construction", that describes the Segre embedding of P 1 ×P 1 ×P 1 and some of its degenerations. In Section 4 we put these two unprojection constructions together as a versal deformation of the anticanonical cone over P(1, 2, 3) over a reducible base, with the obstructions also controlled by the matrix format. We conclude with some general remarks, mnemonics, slogans, and FAQ. We do not pretend any generality, or any theoretical treatment of Gorenstein codimension 4 (compare [G4]).

Social Media is accepted and recognized as the most effective medium in the field of marketing, higher education, customer’s relationship management, electronic word of mouth and in public administration. Social media is an important tool for economic development as its tools provide two-way communication and low-cost marketing, to gain information and communicate and build a relationship with its customers. While public value is used to check the influence of government actions to create values for its citizens. The main objective of this research is to systematically study the literature on social media and public value relationship. By reviewing the 36 articles, out of which 29 articles published in Scopus Index Journal from the year 2011 to 2018 and 7 articles published in Web of Science Index Journal from the year 2014 to 2018, this paper provides the data about these articles. The systematic literature review shows that most work has been done in developed countries. In this review, the main objective of these papers is also discussed.