Abstract. Various superabsorbent polymers (SAPs) were synthesized by free radical copolymerization at 70°C using acrylic acid (AA), potassium acrylate (KA), N-isopropyl acrylamide (NIPAM) and sulfopropyl methacrylate potassium salt (SPM) as monomers, bis [2-(methacryloyloxy)ethyl] phosphate (BMEP) as crosslinker and potassium persulfate (KPS) as initiator. The optimization of the synthesis led to the preparation of a SAP with very high water absorption ability, with a maximum swelling of 2618 g water/g dry hydrogel. The most promising SAP was fully characterized and the absorption capacities were studied at different pH and ionic strengths. When this SAP was mixed with soil, the mixture was able to lose water more slowly. Also, this material revealed high loading capacity and showed good releasing profiles using urea as model fertilizer. Due to these advantageous properties, the synthesized SAP can be used in agricultural applications.

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Carboxymethyl cellulose (CMC) stabilized Fe‐Ni bimetallic nanoparticles (CMC‐bNP‐Fe‐Ni) were used for the reductive degradation of the drug nimesulide (NMS) in aqueous solution and in a secondary effluent. The influence of the concentrations of CMC‐bNP‐Fe‐Ni and NMS as well as the Ni content were investigated systematically. Nanoparticles containing 17 wt% of Ni showed the best performance for the reductive degradation of NMS. A complete removal of NMS was verified with the formation of aromatic by‐products for concentrations of NMS ranging from 10 to 60 mg L−1 using CMC‐bNP‐Fe(0.83)–Ni(0.17) (0.2 g L−1). As the CMC‐bNP‐Fe(0.83)–Ni(0.17) and NMS concentrations increased, so did the removal rate, a result consistent with a heterogeneous reaction carried out under agitated conditions. The degradation of NMS using the CMC‐bNP‐Fe(0.83)–Ni(0.17) system in the presence and absence of dissolved oxygen revealed that oxygen affects the process for NMS concentrations <45 mg L−1. A comparative study using CMC‐bNP‐Fe(0.83)–Ni(0.17), bNP‐Fe(0.83)–Ni(0.17), and CMC stabilized zero‐valent iron nanoparticles (CMC‐ZVIn) revealed that higher degradation levels of NMS were only obtained with the CMC‐bNP‐Fe(0.83)–Ni(0.17) system by means of the reduction of nitro and sulfonyl groups with the formation of aromatic by‐products. The reductive treatment of a secondary effluent with CMC‐bNP‐Fe(0.83)–Ni(0.17) led to a rapid decrease in the NMS concentration, with a percentage reduction of 95% achieved after 5 min of reaction.

Chitosan (CHI)-stabilised Ni–Fe bimetallic nanoparticles (bNP/CHI) were synthesised varying the content of nickel and denoted as 2-bNP/CHI, 17-bNP/CHI, and 27-bNP/CHI. The nanoparticles were characterised using several techniques and used in the removal of nimesulide. XRD and Mössbauer analyses confirmed the formation of an amorphous structure containing Fe0 and Fe2O3 while the FT-IR analysis confirmed the presence of chitosan in the nanoparticles. A very high removal of nimesulide was obtained after only 15 min of treatment with the 17-bNP/CHI system. The by-product obtained after the reductive treatment was identified using the chromatography analysis coupled to the mass spectrometry technique.