As low as 1 ppm concentration of ammonia is sufficient to pose a threat to fish cultured in the fish farm, and therefore effective ammonia removal method is necessary to minimize the ammonia concentration. In this study, cellulose, which is one of the low-cost and highly versatile green polymers, has been modified by TEMPO-mediated oxidation and first applied for ammonia removal from water. For the TEMPOoxidized cellulose of 0.78 mmol/g carboxylate group content, the adsorption capacity was measured to be 8.21 mg/g (empirically, 9.465 mg/g derived from Langmuir isotherm model) from water at pH around 7.0, which is comparable with the existing carbon-based sorbent for the reduction of ammonia. This also indicates close to 100% utilization of the carboxylate adsorption sites. In addition, equilibrium adsorption can be achieved within 5 min. The ammonium adsorption data fit the Langmuir model very well, indicating a monolayer chemical adsorption process. The adsorption performance of the material was minimally influenced by a pH range of 5.0−9.0 but substantially affected by the presence of competing ions. Despite a slight decrease in adsorption performance, the material can be regenerated and applied in a real water sample. Electrostatic interaction and hydrogen bonding between the introduced carboxylate groups and ammonium ions appear to be the adsorption mechanisms governing the material performance in ammonia removal. Further discussion on performance comparison, alternative modification methods, production cost, and potential usage of the postadsorption material is also included.
Highly controllable electronic properties (carrier mobility and conductivity) were obtained in the sophisticatedly devised, structure-controlled, boron-doped microcrystalline silicon structure. Variation of plasma parameters enabled fabrication of films with the structure ranging from a highly crystalline (89.8%) to semi-amorphous (45.4%) phase. Application of the innovative process based on custom-designed, optimized, remote inductively coupled plasma implied all advantages of the plasma-driven technique and simultaneously avoided plasma-intrinsic disadvantages associated with ion bombardment and overheating. The high degree of SiH4, H2 and B2H6 precursor dissociation ensured very high boron incorporation into the structure, thus causing intense carrier scattering. Moreover, the microcrystalline-to-amorphous phase transition triggered by the heavy incorporation of the boron dopant with increasing B2H6 flow was revealed, thus demonstrating a very high level of the structural control intrinsic to the process. Control over the electronic properties through variation of impurity incorporation enabled tailoring the carrier concentrations over two orders of magnitude (1018–1020 cm−3). These results could contribute to boosting the properties of solar cells by paving the way to a cheap and efficient industry-oriented technique, guaranteeing a new application niche for this new generation of nanomaterials.
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