[Ethereum] Cannot convert string to buffer. toBuffer only supports 0x-prefixed hex strings

   var infuraApiKey =process.env.INFURA_API_KEY;
  // var privateKey = process.env.PRIVATE_KEY;

   var web3js = new web3(new web3.providers.HttpProvider("https://kovan.infura.io/v3/"+infuraApiKey));

   web3js.eth.defaultAccount = myAddress;
   var privateKey=new Buffer(process.env.PRIVATE_KEY, 'hex');

//   var toAddress = 'ADRESS_TO_SEND_TRANSACTION';

   //contract abi is the array that you can get from the ethereum wallet or etherscan
   var contractABI =bonusABI;
   var contractAddress =bonusAddress;
   //creating contract object
   var contract =  web3js.eth.contract(contractABI).at(contractAddress);
   var count;
   var nounce;
   var errcode="";
   web3js.eth.getTransactionCount(myAddress, function(err, result) {
        nounce=result;
        var nounceHex = web3js.toHex(nounce);

        var rawTransaction = {"from":myAddress,
        "gasPrice":web3js.toHex(2*1e9),
        "gasLimit":web3js.toHex(920000),
        "to":contractAddress,
        "data":contract.addBonus.getData(bonusType, target, year, month, day, token, bonus, bonusName, ineq),
        "nonce":nounceHex}

        var transaction = new Tx(rawTransaction);
        transaction.sign(privateKey);

        var serializedTx = transaction.serialize();
        web3js.eth.sendRawTransaction('0x'+serializedTx.toString('hex'), function(err1, hash) {
           if (!err1) {
               errcode=hash;
          }
           else
               errcode=err1;
        });
  })