Removal of As(III) and Cr(VI) from aqueous solutions using “green” zero-valent iron nanoparticles produced by oak, mulberry and cherry leaf extracts

Abstract The production of nano zero-valent iron nanoparticles, using the extract from natural products, increased in recent years as it represents green and environmentally friendly method. Synthesis of green zero-valent iron nanoparticles (nZVI) using oak, mulberry and cherry leaf extracts (OL-nZVI, ML-nZVI and CH-nZVI) proved to be a promising approach for As(III) and Cr(VI) removal from aqueous solutions. The oak, mulberry and cherry leaves were chosen because of their high oxidant capacity as an important property for the production of the nZVIs. Also, oak, mulberry and cherry trees are widely distributed and easy to find in Vojvodina, the north province of Serbia. Characterization of produced green nZVI materials confirmed the formation of nanosize zero-valent iron particles within the size of 10–30 nm. Nanoparticles were spherical in shape and represented stable material with minimum agglomeration observed by TEM and SEM morphology measurements. Batch experiments revealed that the adsorption kinetics followed pseudo-second order rate equation. The obtained adsorption isotherm data could be well described by the Freundlich model. In addition, investigated pH effect showed that varying the initial pH value had a great effect on As(III) and Cr(VI) removal. This study indicated that nZVI could be produced by low cost and non toxic method with oak, mulberry and cherry leaf extracts and potentially be used as a new green material for remediation of water matrices contaminated with As(III) and Cr(VI)

Three different clay-supported nanoscale zero-valent iron materials for industrial azo dye degradation: A comparative study

In video streaming it is important that the video stream reaches the users in time, and without errors. To retransmit lost packets in a largescale multimedia video transmission is often unfeasible because of the retransmission delay. Because of that errors require either costly retransmissions or causes a downgrade of performance for the receiving user, an important goal is to minimize the number of errors that occurs when transmitting data during video streaming through a wireless channel. In this paper an adaptation-algorithm is proposed, which adapts itself in such away that the receivers of e.g. the broadcast will receive enough packets in order to be able to FEC-decode the received data in low- as well as high loss-scenarios. The algorithm adapts itself by changing the rate of FEC-encoded redundant packets based on the current packet-loss-rate of the channel, with the aim of optimizing the bandwidth-usage and providing the receiver with playable data meeting deadlines. It adds an additional self-adaptive amount of FEC-encoded redundant packets for each FEC-encoded-session in order to guarantee the ability of the receiver to FEC-decode the data and play the media, even under the conditions in which the inteference-level of the channel increases during the transmission of each such session. Simulations demonstrate that in a wireless channel with a packet loss rate of 10%, using 1000 source packets per FEC-encoded unit, 12.6% redundant packets are required in order to ensure a FEC-decoding-failure probability < 1/1000 .När man streamar video är det viktigt att videostreamen når användarna i tid och utan fel. Att återsända förlorade paket i en storskalig överföring av video är ofta olämpligt p.g.a. den fördröjning som återsändning av paket orsakar. Eftersom att fel kräver antingen kostsamma återsändningar eller orsakar en försämring av prestandan för den mottagande användaren, är det ett viktigt mål att minimera antalet fel som uppstår när man överför data genom en trådlös nätverkskanal. I denna thesis presenteras en anpassningsalgoritm, som anpassar sig själv på sådant sätt att mottagarna av t.ex. broadcast kommer att motta tillräckligt många paket för att kunna utföra en FEC-dekodning av datan i scenarion med både små och stora paketförluster. Algoritmen anpassar sig själv genom att ändra andelen av FEC-kodade redundanta paket baserat på kanalens nuvarande andel av paketförluster, med målet att optimera användandet av bandbredd och att förse mottagaren med uppspelbar data inom deadlines. Andelen FEC-kodade redundanta paket är beräknade så att datan ska kunna dekodas och spelas upp även under de förhållanden där störningsnivån i kanalen ökar under överföringen av datan. Simuleringar, gjorda i en trådlös kanal i vilken 10% av paketen förloras, visar att det med 1000 paket av den ursprungliga datan krävs ytterligare 12.6% redundanta paket per FEC-kodad enhet för att uppnå en sannolikhet för ett misslyckande av FEC-dekodningen < 1/1000